Management Plan for the Horned Grebe (Podiceps auritus) in Ontario

Management plan prepared under the Endangered Species Act, 2007
September 2014

This is an image of the Horned Grebe

About the Ontario management plan series

This series presents the collection of management plans that are written for the Province of Ontario and contain possible approaches to manage species of special concern in Ontario. The Province ensures the preparation of the management plans meet its commitments to manage species of special concern under the Endangered Species Act, 2007 (ESA, 2007) and the Accord for the Protection of Species at Risk in Canada.

What is a species of special concern?

A species is classified as special concern if it lives in the wild in Ontario, is not endangered or threatened, but may become threatened or endangered due to a combination of biological characteristics and identified threats.

What is a management plan?

Under the ESA, 2007, a management plan identifies actions that could be taken to ensure, at a minimum, that a species of special concern does not become threatened or endangered. The plan provides detailed information about the current species population and distribution, their habitat requirements and areas of vulnerability. The plan also identifies threats to the species and sets a clear goal, possible strategies, and prioritized activities needed to address the threats.

Management plans are required to be prepared for species of special concern within five years of the species being added to the Species at Risk in Ontario list as a special concern species.

What’s next?

Nine months after the completion of a management plan a government response statement will be published which summarizes the actions that the Government of Ontario intends to take in response to the plan and the government priorities in taking those actions. The implementation of the management plan depends on the continued cooperation and actions of various sectors, government agencies, communities, conservation organisations, land owners, and individuals.

For more information

To learn more about species of special concern in Ontario, please visit the Ministry of Natural Resources Species at Risk webpage.

Cover photo credit: Brian Small

Recommended citation

Kirk, D. A. 2014. Management Plan for the Horned Grebe (Podiceps auritus) in Ontario. Ontario Management Plan Series. Prepared for the Ontario Ministry of Natural Resources and Forestry, Peterborough, Ontario. viii + 32 pp.

Cover illustration: photo credit Brian Small

© Queen’s Printer for Ontario, 2014

ISBN 978-1-4606-4435-5 (PDF)

Content (excluding the cover illustration) may be used without permission, with appropriate credit to the source.

Cette publication hautement spécialisée «Management plans prepared under the Endangered Species Act, 2007», n'est disponible qu'en anglais en vertu du Règlement 411/97 qui en exempte l'application de la Loi sur les services en français. Pour obtenir de l'aide en français, veuillez communiquer avec le ministère des Richesses naturelles au 1-800-667-1940.


David Anthony Kirk


The author would like to thank the following who provided information on Horned Grebes in Ontario and elsewhere in their range: Karen Barry (Bird Studies Canada, British Columbia), Ron Bazin (Wildlife Biologist, Canadian Wildlife Service), André Breault, (Wildlife Biologist, Canadian Wildlife Service), Wendy Calvert (Wildlife Biologist, Canadian Wildlife Service), Doug Campbell (University of Guelph), Jennifer Chipault (USGS National Wildlife Health Center), Dave Elder (Biologist, Michigan), Rob Foster (Northern Bioscience), Al Harris (Northern Bioscience),

Craig Hebert (Canadian Wildlife Service), Leo Heyens (Ontario Ministry of Natural Resources and Forestry), Catherine Jardine (Bird Studies Canada), M. Lubeck (USGS, Colorado), Jon McCracken (Bird Studies Canada), Dave Moore (CWS, Ontario Region), Neal Niemuth (US Fish and Wildlife Service, North Dakota), Cynthia Paszkowski (University of Alberta), Dan Routhier (University of Saskatchewan), Bonita Sample (Minnesota Breeding Bird Atlas), Candan Soykan (Christmas Bird Counts, National Audubon Society), Christopher Sharp (CWS, National Capital Region), Al Smith (retired Canadian Wildlife Service, Saskatoon), Ron Summers (Royal Society for the Protection of Birds, Scotland, UK), Donald Sutherland (Natural Heritage Information Centre, Ontario Ministry of Natural Resources and Forestry), John Van den Broeck (Ontario Ministry of Natural Resources and Forestry), Scott Wilson (Environment Canada), John Woodcock (Thunder Cape Bird Observatory) and Alan Wormington (Consultant, Leamington).


The management plan for the Horned Grebe was developed in accordance with the requirements of the Endangered Species Act, 2007 (ESA). This management plan has been prepared for the Government of Ontario, other responsible jurisdictions and for the many different constituencies that may be involved in managing the species.

The management plan does not necessarily represent the views of all of the individuals who contributed to its preparation, or the official positions of the organizations with which the individuals are associated.

The goals, objectives and management approaches identified in the plan are based on the best available knowledge and are subject to revision as new information becomes available. Implementation of this plan is subject to appropriations, priorities and budgetary constraints of the participating jurisdictions and organizations.

Success in the management of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this plan.

Responsible jurisdictions

Ontario Ministry of Natural Resources and Forestry
Environment Canada – Canadian Wildlife Service, Ontario
Parks Canada Agency
Department of Fisheries and Oceans

Executive summary

The Horned Grebe (Podiceps auritus) is a small, duck-like, sometimes semi-colonial, waterbird. In breeding plumage it is unmistakable, with golden fan-shaped 'horns' behind the eyes contrasting with black facial feathers, chestnut neck and flanks, dirty white belly and dark-coloured back. It is a medium-distance migrant and returns to Ontario shortly after ice break-up in late March or early April (peaking in mid-April).

Horned Grebes nest on small ponds, protected bays or larger lakes within wetlands of at least 0.05 ha in extent and usually of 1 to 10 ha. They nest in deeper (usually fishless) ponds with less dense emergent vegetation than does the Pied-billed Grebe Podilymbus podiceps. Horned Grebes are influenced by water levels and are opportunistic in their selection of nest sites. They appear to be sensitive to disturbance by humans and will abandon nests where there is human activity nearby.

Autumn migration occurs from early September to late December, peaking in late October to mid-November. In autumn, Horned Grebes migrate nocturnally southwards in small flocks over the continent and spend the winter offshore and on some inland waters.

The Horned Grebe is listed as critically imperilled in Ontario by NatureServe. It is vulnerable in Manitoba and the disjunct eastern population, which breeds on the Magdalen Islands in Québec, is critically imperilled and designated by COSEWIC as endangered. The species has not been assessed in neighbouring states in the United States. Historically, the Horned Grebe was thought to breed throughout much of the province of Ontario. However, many observations were based on nest records. It was later discovered that many of these were, in fact, of Pied-billed Grebes, the eggs of which are hard to distinguish in the field from those of the Horned Grebe. The Horned Grebe is distributed widely throughout western Canada, but is on the edge of its eastern range in Ontario.

Surveys done during the first Ontario Breeding Bird Atlas (1981–1985) confirmed breeding in the Fort Severn area as well as possibly in the St. Clair marshes and Rondeau Provincial Park. Prior to this, no breeding had been confirmed since 1938. In the second atlas (2001–2005), three nesting locations were found, none of which were occupied during the first atlas. It has been suggested that the provincial population is comprised of less than 10 breeding pairs annually, though it is likely that other pairs breed undetected in remote locations. Although the North American Breeding Bird Survey (BBS) has limitations for surveying waterbirds, it is the best source of standardized trend data for the species. Analyses show negative trends for most states, provinces and Bird Conservation Regions, and Canada overall (note: trend analyses specific to Ontario are not possible because of the very small numbers of sightings). Although long-term trends (1970–2011) demonstrate a significant decline in Canada, short-term trends (2001–2011) suggest that the declines may have levelled off. Christmas Bird Count (CBC) data suggest a long-term decline in the continental population, but this survey probably misses many of the wintering individuals in the Atlantic. Some Horned Grebes are counted at bird observatories during migration, but trend analyses have not been conducted; at Long Point there was a significant long-term decline, but the greatest rate of decrease was in the 1980s.

Little information exists on threats to the Horned Grebe, and those that are suggested are largely speculative. Factors that influence wetland quality are believed to be most important – including agricultural run-off (fertilizers) that could cause eutrophication, and pesticides that could have toxic impacts. Either could impact aquatic invertebrates as well as fish populations at breeding ponds or wetlands used during migration. Direct wetland habitat loss (filling or draining) is also a factor, as well as surrounding land uses that influence water levels (e.g., tile drainage). Climate change also has the potential to influence water levels. It has been speculated that interspecific competition may be occurring with other grebe species – particularly the Red-necked Grebe Podiceps grisegena, and Pied-billed Grebe. Cumulative effects on Horned Grebes are uncertain but could include habitat loss, invasive species and climate change. In the wintering areas, oil spills in marine areas may pose a significant threat as the species appears to be especially susceptible to oiling. Grebes also appear to be vulnerable to botulism and perhaps some other diseases. Determining management options to conserve Horned Grebe are difficult in the absence of more information about the species' distribution and abundance, and the small Ontario breeding population.

The goal of this management plan is to formulate strategies for increased and more effective collaboration with provinces in central and western Canada that have greater proportional responsibility for the species, and to determine how management objectives for the species may be achieved.

In order to attain this goal, a series of objectives have been developed. Achieving these objectives will rely on the support and cooperation of interested stakeholders – including especially other provincial governments, municipalities, landowners, First Nations, non-government organizations and the Ontario government. The objectives are listed below.

  1. Determine the distribution and abundance of breeding Horned Grebes in Ontario; identify migration stopover and wintering arears.
  2. Determine local and landscape level habitat requirements for Horned Grebe in Ontario.
  3. Identify the main threats to the Horned Grebe (initially using the IUCN threats calculator).
  4. Through a multispecies approach, that includes the Horned Grebe and other wetland species, maintain or expand existing wetland habitat, as well as restore or create new wetlands.
  5. Develop landowner agreements and management activities to secure, protect, enhance and restore potential wetland habitats for Horned Grebes and other wetland species.
  6. Encourage aboriginal communities to develop stewardship projects and activities that involve wetland species at risk and especially the Horned Grebe.

1.0 Species assessment and classification

Common name: Horned Grebe
Scientific name: Podiceps auritus
SARO List Classification: Special Concern
SARO List History: Data deficient
COSEWIC Assessment History: Special Concern (2009)
SARA Schedule 1: Not listed

Conservation status rankings:


The glossary provides definitions for the abbreviations above.

2.0 Species information

2.1 Species description and biology

Species description

The Horned Grebe is a typical small grebe (300-570 g, 31-38 cm in length). There are two subspecies: Podiceps auritus cornutus in North America and Podiceps auritus auritus in Europe and Asia. In Europe, the Horned Grebe is known as the Slavonian Grebe. On the basis of shared characteristics such as behavioural displays and the plumage pattern of the downy young, the Horned Grebe is believed to be more closely allied with the Red-necked Grebe P. grisegena, and Great Crested Grebe P. cristatus than the smaller grebe species (Storer 1963, 1969, Fjeldså 1973a, 1982).

The Horned Grebe has a long neck, and its bill is short, straight, pointed, and pale-tipped. The forehead is flat with a short peak at the rear of the crown. In breeding plumage the most distinctive feature is the facial 'horns' on both sides of the face. These are fan-shaped patches of bright buff or golden feathers behind the eye (erected during courtship), and they contrast with the black, fan-shaped feathers on the face. The foreneck, lores, upper breast and flanks are chestnut in colour, while the crown and back are blackish and the belly is a dirty white. During the nonbreeding season the plumage is more nondescript and appears black and white at a distance. The slate-grey crown borders white cheeks which extend almost around the nape; the border between the crown and cheeks extends in an almost straight line behind the eye and generally there is a whitish spot over the lores in front of the eye. The black feathers on the nape narrow to a thin black line. The neck is whitish, sometimes with a dusky wash on the lower part. During flight, the Horned Grebe displays white secondary feathers and a small white patch at the base of the upper forewing (which is sometimes reduced or absent). Although the sexes are similar, males in breeding plumage are slightly larger and brighter in colouration (Stedman 2000).

The grebe species that is most similar to the Horned Grebe in Ontario and globally is the Eared Grebe (Podiceps nigricollis); however, the Eared Grebe differs in that the steep forehead rises to a peak in the centre of the crown (compared to the rear of the crown in the Horned Grebe).

In addition, the neck is more slender, the bill thinner and more upturned, the back more rounded and the tail end has fluffier feathers than in the Horned Grebe. In flight, the Eared Grebe does not have whitish patches at the base of the upper forewing. Finally, in breeding plumage, the Eared Grebe has a black head and yellowish, wispy fan-shaped ear tufts behind the eye; in winter plumage it is distinguished from the Horned Grebe by the black feathers on the head bulging downwards below the eye and separating the white cheeks (Stedman 2000).

Species biology

The Horned Grebe is thought to be strongly monogamous with occasional cases of polygyny (a male pairing with two females). Evidence suggests that Horned Grebes likely do not maintain their pair bond over the winter, but fidelity to breeding territories allows some pairs to re-establish bonds the following spring. In these few pairs there is sustained monogamy, but it is possible that most pairs do not stay together (A. Breault, pers. comm. 2014). Pair-bonds develop during mid-to late-winter and pairs may remain in flocks until arriving in their breeding areas.

A variety of elaborate displays are used for pair-bonding and these ceremonies are similar to those of other grebe species (summarized by Cramp and Simmons 1977). They include the 'Discovery Ceremony', the 'Weed Ceremony', the 'Head-Shaking Ceremony' and the 'Triumph Ceremony' (see Cramp and Simmons 1977). Horned Grebes tend to nest solitarily and are very territorial, but in some circumstances they are loosely colonial.

Nests are built in shallow wetlands in emergent vegetation within a few metres of open water Specific characteristics of wetlands are required for Horned Grebe nest sites, including size, vegetation characteristics and water depth. Horned Grebes prefer small water bodies (marshes and ponds) as demonstrated by findings in Manitoba, Saskatchewan and North Dakota (Ferguson and Sealy 1983, Faaborg 1976, Sugden 1977). In Manitoba, Ferguson and Sealy (1983) found that the mean pond size selected was 1.2 ha and ranged from 0.1 to 8.4 ha (n=65 ponds). In Saskatchewan, the pond type that was used most averaged 1.17 ha in size, whereas the second most used pond type averaged 0.42 ha (Sugden 1977).

Both North American and European studies indicate that water depth at the nest site must be at least 20 cm deep so that adult Horned Grebes can approach the nest from underwater. Based on 119 measurements of water depth, mean depth in Manitoba was 39.2 cm (Ferguson and Sealy 1983). Permanency of water is also important for Horned Grebes. In Saskatchewan, Sugden (1977) found that the most-used ponds had a depth of approximately 120 cm. They also had the largest area of open water, although water was scarce in some ponds by July. Ephemeral wetlands that dried up by July were either not used at all or little used.

Nest building begins shortly after arrival in the breeding areas and is strongly dependent on weather. Prior to building substantial nests, copulation platforms may be built. Nests are constructed from material immediately surrounding the nest site. Dominant species growing near Horned Grebe nests in Manitoba were whitetop Scolochloa festucacea, bulrushes Scirpus spp. and cattails Typha spp. (Ferguson and Sealy 1983). The time between nest site inspection and completion of the nest varies from three to four hours up to two to three days (Ferguson 1977).

In Ontario, Horned Grebe nests may contain eggs from mid-May to the end of June (Peckand James 1983). Dates of first clutch initiation are similar in both southern and northern sites (17 May to 11 June in Manitoba; Ferguson and Sealy 1983, 20 May to 11 June in the Northwest Territories; Fournier and Hines 1999). Normally, clutches in Manitoba ranged from three to eight eggs with a mean of 5.9 (81% of nests had 5, 6 or 7 eggs; Ferguson and Sealy 1983). The date of first egg hatching was between 10 June and 2 August in Manitoba (Ferguson and Sealy 1983), whereas in the Northwest Territories most clutches (69%) hatched between 21 and 27 June (Fournier and Hines 1999). The incubation period is 23 to 25 days and young depart the nest immediately after hatching (Stedman 2000). As in several other grebe species, young are carried and brooded on their parents' backs. During their first three days of life this is done almost continuously but the frequency of carrying decreases over time (7-10 days). Usually chicks are brooded for nine days following hatching and are fed for 14 days (Stedman 2000). When all of the young have hatched, the parents may separate the brood, and each parent cares for the split brood. This phenomenon occurs more frequently in the case of large broods (Stedman 2000).

Young Horned Grebes take their first flight at 41 to 50 days of age (Stedman 2000). Generally, one brood is reared each breeding season, but sometimes there are two or more broods. If the first clutch is lost then usually replacement clutches are laid, but these often fail and rarely fledge young successfully (Stedman 2000). From a sample of 637 nests in Manitoba, hatching success was 30.3 percent (Ferguson and Sealy 1983), whereas in 1,332 nests from Iceland and Norway it was 63 percent (Fjeldså 1973b). Most egg loss in Manitoba was attributed to predation, mostly by Raccoons (Procyon lotor). Predation of Horned Grebe eggs can be severe, but quantifying the impact of nest predation on population viability is challenging. Confirmed and possible predators other than Raccoons include American Crow (Corvus brachyrhynchos), Black-billed Magpie (Pica hudsonia), American Coot (Fulica americana) and gull species (Larus spp.). Also in Manitoba, 72 percent of chicks survived until they were ten days old and most mortality occurred within the first few days following hatching. Sixty-four percent of chicks fledged from an average brood size of 4.3. This translated to a productivity of 2.75 per pair per year (Ferguson and Sealy 1983). Comparable numbers from Europe were 62.5 percent of chicks surviving until ten days old and 53 percent surviving 20 days (Fjeldså 1973b).

Generally a pair of birds will defend a small pond for their exclusive use, but in larger ponds and wetlands, two pairs may occur. There is a negative relationship between territory size and habitat quality (richness of food supply or availability of nest sites). Where habitat quality is very high, Horned Grebes are loosely colonial (Stedman 2000). Experienced pairs tend to select breeding areas with protective cover and so by implication may have higher success rates than first-time breeding pairs that select areas with lower densities of vegetation (Fjeldså 1973a, 1973b).

Horned Grebes are nocturnal migrants, travelling at night overland on a broad front from inland breeding populations and along the Pacific and Atlantic coasts (Stedman 2000). They are thought to follow the Atlantic or Mississippi flyway en route to the Atlantic Coast or the Gulf of Mexico (COSEWIC 2009). However, in some areas diurnal migration occurs (A. Wormington, pers. comm. 2014).

The maximum age recorded for the species is five years and two months (Clapp et al. 1982). Little information exists on survivorship of Horned Grebes. Because some individuals winter in marine waters, metal bands can corrode and there are low rates of band recovery (Clapp et al. 1982, Stedman 2000). As well, few Horned Grebes are banded. For example, of the 403 Canadian Horned Grebes banded, only 11 were recovered between 1921 and 1995 according to the Canadian Wildlife Service’s atlas of Bird Banding (Dunn et al. 2009). Of these records, five included birds that were banded in the eastern or northern prairies; these were either recovered on the east coast or between the banding location and the east coast. Some Horned Grebes from Saskatchewan may winter along the Pacific coast as demonstrated by a bird that was banded in Oregon in December and recovered in Saskatchewan in May. Another individual banded as young in its natal areas in Alberta was recovered in Beach Grove, British Columbia (Dunn et al. 2009).

The Horned Grebe is highly territorial, defending a one ha area around the nest from other grebes and other small or medium-sized bird species (Stedman 2000). Unfortunately, information on pair and site fidelity is sparse because of the lack of consecutive banding recoveries from the same pairs in the wintering and breeding areas. In some dry years in the central interior of British Columbia, Horned Grebes may have "multiple" philopatry where some known nesting birds visit the breeding areas early in the spring and then depart again after a few days (A. Breault, pers. comm. 2014). In Manitoba, Ferguson (1981) re-captured seven of 50 grebes (43 adults, seven juveniles). Five of the seven recaptures returned to the same ponds where they had successfully bred the year previously. There was one instance of a nesting pair that returned to the same territory in two consecutive years (1975 and 1976). Some unconfirmed information on high pair fidelity comes from Sweden (Fjeldså 1973c) as well.

During the winter, flocks occur regularly each year at some sites – both in North America and Europe (Stedman 2000).

In summer, the diet of the Horned Grebe is mainly aquatic arthropods; some aerial arthropods are also eaten. In the winter, a wider variety of species are taken, including fish, crustaceans (especially amphipods and crayfish – at least in North America), and polychaetes. Benthic invertebrates (rather than mid-water species) are taken more often during the winter (Madsen 1957, Ainley and Sanger 1979). Exhaustive studies of diet have been undertaken in North America (e.g., McAtee and Beal 1912) but unlike Europe (Fjeldså 1973c), little investigation of seasonal variation has been done (Stedman 2000). In Scotland, productivity in Horned Grebes is linked to abundance of Chironimidae (Brooks et al. 2013). In North America by volume, invertebrates were most important, followed by fish, crustaceans, small frogs, salamanders, leeches and tadpoles (Westmore 1924). As in other grebe species, Horned Grebes swallow feathers to aid in digestion of fish bones.

North American young Horned Grebes are eaten by Northern Pike (Esox lucius – Ulfvens 1988) and gulls, while adults are preyed on by American Mink (Neovison vison) (Arnold and Fritzell 1990, Eberhardt and Sargeant 1977). There is also an anecdotal observation of a Great Blue Heron (Ardea herodias) attempting to kill a Horned Grebe in Oregon (Walravens 1985).

2.2 Population and distribution

The Horned Grebe has a holarctic distribution, meaning it is found in the world’s northern continents. It occurs at low population densities throughout temperate and boreal regions. There are two subspecies: Podiceps auritus cornutus which breeds throughout western North America and Podiceps auritus auritus which breeds in Europe (del Hoyo et al. 1992).

Over 92 percent of the North American population breeds in Canada (COSEWIC 2009) where its range (Figure 1) extends from "British Columbia eastwards to the Ontario-Manitoba border and northwards into the Yukon and Northwest Territories" (Cadman et al. 2007, Atlas of the Breeding Birds of Ontario 2001–2005, p. 144).

Within Canada, there are two populations of Horned Grebe: the western population and the Magdalen Islands population in Québec. Ontario is at the extreme eastern periphery of the range of the western population.

Figure 1. Distribution of Horned Grebe in North America (Stedman 2000, used with permission from Birds of North America online maintained by the Cornell Lab of Ornithology).

This is a map of North America depicting the distribution of the Horned Grebe for breeding and wintering.

Enlarge figure 1 breeding distribution map of Horned Grebe

Determining the distribution and abundance of Horned Grebes accurately in Ontario is complicated by four factors. Firstly, although Hoar (2007) estimated the provincial population at 10 pairs, some potential breeding sites in northwestern and northern Ontario have not been surveyed. Second, Horned Grebe eggs can be mistaken for those of the Pied-billed Grebe, and thus many nest records could be invalid (D. Sutherland, pers. comm. 2014). Third, much of the Horned Grebe population consists of non-breeders, making confirmation of nesting challenging. Finally, since fledged juvenile grebes retain their plumage until the autumn, sightings of juveniles are not necessarily confirmation of breeding at a particular location, since these individuals could have hatched elsewhere.

The Horned Grebe is a rare and irregular breeder in Ontario (Hoar 2007). One of the best sources of data come from the Atlas of Breeding Birds of Ontario, which was first carried out between 1981 and 1985 (Cadman et al. 1987), and then repeated 20 years later between 2001 and 2005 (Cadman et al. 2007) (Figures 2 and 3). During the first atlas, Horned Grebes were confirmed breeding in the Fort Severn sewage lagoons in the northwest, and possibly breeding in the St. Clair marshes and Rondeau Provincial Park marshes in the southwest (Eagles 1987). However, none of these sites were occupied in the second atlas when Horned Grebes were found nesting at Opasquia Provincial Park, Pikangikum Lake and the Rainy River sewage lagoons (Hoar 2007).

Figure 2. Distribution of Horned Grebes in Ontario based on the First Breeding Bird Atlas of Ontario (1981–1985). Used with permission (Source: Cadman, M.D., D.A. Sutherland, G.G. Beck, D. Lepage, and A.R. Couturier (eds.). 2007. Atlas of the Breeding Birds of Ontario, 2001–2005. Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, and Ontario Nature, Toronto, xxii + 706 pp.).

This is a map illustrating the first breeding evidence of the Horned Grebe in Ontario.

Enlarge figure 2 first breeding evidence map of Horned Grebes

Figure 3. Distribution of Horned Grebes in Ontario based on the Second Breeding Bird Atlas of Ontario (2001–2005). Used with permission (Source: Cadman, M.D., D.A. Sutherland, G.G. Beck, D. Lepage, and A.R. Couturier (eds.). 2007. Atlas of the Breeding Birds of Ontario, 2001–2005. Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, and Ontario Nature, Toronto, xxii + 706 pp.).

This is a map illustrating the second breeding evidence of the Horned Grebe in Ontario.

Enlarge figure 3 map second breeding evidence

In the Birds of Quetico Provincial Park and the Atikokan Area, Elder (1994) recorded a possible breeding record for Marmion Lake, just north of Atikokan. However, the source of this record has not been found (D. Elder, pers. comm. 2014).

It is probable that Horned Grebes which breed in northwestern Ontario are linked genetically to those in Manitoba, and are thus part of the western population.

During winter Horned Grebes occur in nearshore marine coastal waters, including sheltered bays, lagoons and estuaries (del Hoyo et al. 1992, Ogilvie and Rose 2003, Paton et al. 2010). They also occur in a range of inland water bodies, including inland large lakes and rivers. In Ontario, Horned Grebes are recorded during Christmas Bird Counts (CBCs) on Lake Ontario. They have also been recorded on the Lake Ontario Mid-winter Waterfowl Count and the more recent January Lower Great Lakes Waterfowl Survey carried out by Long Point Waterfowl. Typically, however, only low numbers are seen during the latter survey and so they are not recorded (T. Barney, pers. comm. 2014).

The specific wintering locations of Ontario breeding Horned Grebes are unknown. Birds from the prairies, including those breeding in Ontario, move south overland towards the Atlantic coast and the Gulf of Mexico. Christmas Bird Counts (CBCs) demonstrate that 41 percent of Horned Grebes winter on the Pacific coast, 47 percent on the Atlantic coast (including Florida), 6 percent of birds in states bordering the Gulf of Mexico (i.e., Texas, Louisiana, Mississippi and Alabama) and 6 percent in other inland states (National Audubon Society 2006 cited in COSEWIC 2009). Fewer individuals winter inland in eastern North America as far as the northern United States and southern Canada and these are mostly on the lower Great Lakes (Godfrey 1986, American Ornithologists Union 1998).

Horned Grebes are counted regularly on spring and fall migration at various bird observatories in Ontario such as Long Point (J. McCracken, pers. comm. 2014) and Thunder Cape (J. Woodcock, pers. comm. 2014). Horned Grebes are also regular spring and fall migrants in the Rainy River District of Ontario (D. Elder, pers. comm. 2014). During late spring, ice break-ups, large concen- trations of waterfowl, including Horned Grebes, may congregate in open water (e.g., at the mouth of the Rainy River, where it empties into Lake of the Woods, > 500 Horned Grebes were counted on 6 May 1996; a similar situation occurred in 2013 at the outlet of Rainy Lake at Fort Frances; D. Elder, pers. comm. 2014). Horned Grebes are also sometimes seen in various inland Important Bird Areas (IBAs) such as the recent spring count of 170 birds on 2nd May 2014 at the Lake Deschênes IBA on the Ottawa River (T. Cheskey, pers. comm. 2014).

The numbers of Horned Grebes migrating through Ontario on fall and spring migration are shown in Figures 2 and 3 (data summarized for the period 1970–2014; eBird 2014). The highest average number of birds (18.7 birds) and highest count (3,000 birds) was on the week beginning 15th April. On fall migration, the highest average numbers were in the week beginning on the 22nd October and the highest count was in the week beginning on the 15th November (314 birds). During the winter season, the highest average count (3.8) and the highest count (80) was in the week beginning on the 1st December.

Figure 4. Fall (August to November) migration counts of Horned Grebes in Ontario over the period 1970–2014. (Source: eBird).

This is a an image of two charts indicating the average and high migration count of the Horned Grebes in Ontario. The lowest average and highcount was under two on August 1<sup>st</sup>. The highest average was recorded between September 26 and October 24. The highest count recorded was November 21st.

Figure 5. Spring (March to May) migration counts of Horned Grebes in Ontario over the period 1970–2014. (Source: eBird).

This is an image depicting the average and high count of the spring migratoin of the Horned Grebes in Ontario.

In the eastern part of the range (including Ontario), it is likely that most birds winter along the Atlantic coast and in the Gulf of Mexico. Fewer individuals winter inland in eastern North America as far as the northern United States and southern Canada and these are mostly on the lower Great Lakes (Godfrey 1986, American Ornithologists Union 1998).

Horned Grebes winter along the Pacific Coast of North America from the Aleutians and south coastal Alaska to northern Baja California (Stedman 2000). Mostly south of 38°N, where average January temperatures are warmer than -1° C, Horned Grebes also spend the winter on inland water bodies (lakes, rivers, and reservoirs; Root 1988, Stedman 2000). For example, during Christmas Bird Counts (CBC) they have been recorded wintering inland in central Maryland, eastern Virginia, eastern North Carolina, central South Carolina, northern Georgia, Florida (except the southern Florida peninsula), Tennessee, and from north-central Arkansas, northern and southeastern Louisiana west through southeastern Oklahoma and northeastern Texas (Stedman 2000). In Texas, more Horned Grebes are found inland than on the coast (A. Wormington, pers. comm. 2014).

Population trends

The Horned Grebe has been showing long-term declines and range contraction in North America according to the North American Breeding Bird Survey (NABBS). Long-term NABBS analysis demonstrates that the probability of a Canada-wide decrease between 1970 and 2011 was 95% (annual trend index -1.74, medium reliability based on 151 routes; Environment Canada 2014). Most of the NABBS routes (and the prairie pothole stronghold of the Horned Grebe) are in Alberta and Saskatchewan, both of which show long-term decreases similar to the continental trend. However, over the short-term (2001–2011), there is evidence that numbers of Horned Grebes have stabilized and trends are positive; the probability of there being an increase over the short-term was 78% Canada-wide (Environment Canada 2014).

Based on the Christmas Bird Count, previous trend analyses demonstrated significant long-term (1966–2005) declines in Horned Grebes continental-wide of 1.5 percent per year (National Audubon Society 2006) or a population decrease of approximately 45 percent since the mid-1960s (COSEWIC 2009). However, the most recent CBC analyses demonstrates that although declines were evident until the late 1990s, in the early 2000s these declines levelled off and trend estimates are positive (no change) at the continental level (C. Soykan, pers. comm. 2014).

Horned Grebes have been counted over a 50 year period at Long Point Bird Observatory and over a 15 year period at Thunder Cape Bird Observatory. At Long Point, there was a significant long-term decline in spring counts of Horned Grebes over the period from 1961 to 2011 (annual % change -5.0% per year, P = 0.01 (J. McCracken, pers. comm. 2014). The steepest declines occurred prior to the mid-1980s and numbers of grebes have been stable since then. No statistically significant trends have occurred in autumn counts over any period (J. McCracken, pers. comm. 2014). Fewer birds pass through Long Point in the autumn which may account for why no significant trends were found at this time of year. The most recent counts at Long Point show maximum high spring counts of 191 Horned Grebes in 2013, 41 in 2012, 65 in 2011, 16 in 2010 and 3 in 2009. Maximum high autumn counts were 26 in 2013, 2 in 2012, 2 in 2011, 0 in 2010 and 2 in 2009.

Recent counts at Thunder Cape Bird Observatory showed fairly large inter-annual variation. Over the last four years peak/highest daily numbers of Horned Grebes observed per year’s fall were 53 in 2010, 87 in 2011, 14 in 2012, and 69 in 2013 (J. Woodcock, pers. comm. 2014). The breeding origin of these birds is unknown but may include northwestern Ontario and Manitoba.

2.3 Habitat requirements

In much of their Canadian range, Horned Grebes prefer shallow wetlands and nest in the edges of these wetlands in emergent vegetation adjacent to open water (Hoar 2007, Kindopp 2006, Routhier 2012). They prefer small ponds or the protected bays of lakes within wetlands of at least 0.05 ha in extent and usually of 1 to 10 ha. They nest in emergent vegetation provided that it is not too dense. They nest in deeper (usually fishless) ponds and less dense emergent vegetation than the Pied-billed Grebe Podilymbus podiceps. Positive relationships between the abundance of certain invertebrate groups (clams – class Bivalvia, damselflies - suborder Zygoptera, and copepods or small crustaceans – order Cyclopoida) and shoreline irregularity was found for wetlands used for brood-rearing by Horned Grebes in the Northwest Territories (Kindopp 2006). Conversely, there was a negative relationship between abundance of Caddisflies (order Trichoptera) and brood-rearing wetlands for Horned Grebe.

It has been stated that Horned Grebes prefer microhabitats with the greatest degree of interspersion of water and vegetation (hemi-marsh) and that these habitats are still selected regardless of changes in water levels (Barnes and Nudds 1990). No studies have been carried out to determine the landscape level requirements of Horned Grebes, except for the recent study by Routhier (2012) in the prairies.

Routhier (2012) found that breeding occupancy of wetlands by Horned Grebes could be predicted by the number of wetlands (permanent, semi-permanent and artificial) at the landscape scale in 2010 but not in 2011. In 2011, Horned Grebe occupancy and productivity was higher in landscapes with low wetland density. He attributed this to inter-annual changes in water conditions and suggested that Horned Grebes were opportunistic and would occupy landscapes with low wetland densities in years of above-average rainfall.

Horned Grebes readily adapt to human-created habitats. They have bred in human- created ponds in eastern Ontario (Locky et al. 2005) and also in borrow pits (excavated pits that fill with water after removal of gravel or sand) in Alberta (Kuczynski and Paszkowski 2005) and in the Northwest Territories and Yukon (Fournier and Hines 1999). In Scotland, the area of sedge (Carex spp.) nesting vegetation at Loch Ruthven has been artificially expanded to encourage nesting Horned Grebes (Ogilvie and Rose 2003). During the second Ontario Breeding Bird Atlas, they were found nesting in the Rainy River sewage lagoons. Moreover, of 575 boreal forest breeding sites surveyed in the Northwest Territories between 1986 and 1996, more than half were flooded borrow pits (Fournier and Hines 1999).

2.4 Characteristics contributing to vulnerability of species

Because Horned Grebes nest in wetlands they are subject to a variety of aquatic contaminants that occur in water bodies as a result of agricultural run-off and other sources (Forsyth et al. 1994). They are also area sensitive and appear to only nest in wetlands of a minimum size (Stedman 2000).

Horned Grebes are sensitive to human disturbance and also vulnerable to nest predation (Stedman 2000).

3.0 Threats

Natural ecosystems are continually evolving in response to a variety of forces and factors. But they are limited in their ability to adapt to rapid change, such as that introduced through human activities. Humans sometimes disrupt and degrade biodiversity through habitat loss, introduction of invasive species, population growth, pollution, unsustainable use and climate change. Our growing population combined with our rising levels of resource consumption can threaten biodiversity (OBC 2011). Recently, an assessment of pressures on Ontario’s biodiversity showed that many threats are increasing (OBC 2010).

The following threats have been identified as currently facing the Horned Grebe:

Habitat loss:

Wetland loss through conversion to other uses is a major threat to the Horned Grebe. The extent of this threat in the main potential Ontario breeding areas in the northwest is largely unknown. However, much of the Rainy River region is agricultural and so wetlands are vulnerable to loss through drainage and conversion to farmland. In southern Ontario, where Horned Grebes use wetlands during migration and occasionally breed, much more is known about the rate of wetland loss. A recent study found that wetland loss is continuing in much of southern Ontario and over 72 percent of wetlands have been lost since pre-European settlement (Ducks Unlimited 2010).


Various diseases could threaten Horned Grebes which breed or migrate through Ontario. These include West Nile Virus and botulism (probably all type E in the Great Lakes).

Transmitted by two mosquito species (mainly Culex pipiens and Culex tarsalis, in eastern and western North America respectively), West Nile Virus (WNV) is an arbovirus (a disease transmitted by arthropods) which affects bird species in temperate areas mostly in the late summer and fall. While only two species of grebe were impacted by WNV prior to 2013 (Pied-billed Grebe and Clark’s Grebe (Aechmophorus clarkii), in that year up to one percent (10,000) of the two million Eared Grebes that winter on Great Salt Lake were impacted (Sleeman 2014). No cases have been reported of Horned Grebes infected with WNV, but the recent case of mortality in the closely related Eared Grebe suggests that this is a possibility.

The most significant disease threat to Horned Grebe comes from Type E and perhaps Type C Botulism. Generally Type C Botulism is more common and affects mostly waterfowl in wetlands, lakes and ponds; Type E Botulism is less common and in North America is confined to the Great Lakes. It is believed to be caused by ecosystem changes in the Great Lakes and perhaps facilitated by invasive species. First identified in Ontario in 1998, outbreaks of Type E Botulism have occurred annually in Lake Huron, Lake Erie and Lake Ontario (Campbell and Barker 1999, CWHC n.d.). Thousands of loons, diving ducks, mergansers, grebes, gulls, and shorebirds have been killed during these events. Botulism is thought to have caused 100,000 bird fatalities on the Great Lakes since 1999 (Lubek 2014). There are many avenues by which Horned Grebes could be infected with Type E Botulism, including consumption of contaminated fish and invertebrates (Perez-Fuentetaja et al. 2008).

Type E Botulism has been confirmed in Horned Grebes, Red-necked Grebes and Eared Grebes (USGS 2014, D. Campbell, pers. comm. 2014). For example, between 2004 and 2013, the USGS National Wildlife Health Center received reports of 660 known (2,304 estimated) dead Horned Grebes recovered on Great Lakes shores and associated with confirmed or suspect botulism type E mortality events in Wisconsin, Michigan, Pennsylvania, New York, and Ontario (J. Chipault, pers. comm. 2014). Unfortunately, assessing the extent of botulism mortality to Horned Grebe populations is challenging due to limitations of testing methods and a lack of samples found and tested (D. Campbell, pers. comm. 2014).


Horned Grebes are susceptible to pollution in their breeding areas, on stopover migration and in their wintering areas. For example, many lakes and wetlands are exposed to contaminants through agricultural run-off and atmospheric deposition (e.g., rain). Many aquatic species, including grebes, are exposed to bioaccumulation of metals such as lead and mercury, as well as selenium, cadmium and arsenic (Burger and Eichorst 2007). These metals can have direct toxic effects or can cause behavioral abnormalities or neurotoxicological effects (e.g., Scheuhammer et al. 2008). Eggs of Horned Grebes in the Canadian prairies contained DDE and PCBs in all cases, and dieldrin, mirex and oxychlordane were present in low levels. Mercury was also present at low levels (Forsyth et al. 1994).

Horned Grebes appear to be extremely vulnerable to oil spills during the overwinter period (del Hoyo et al. 1992, Ogilvie and Rose 2003, Fjeldså 2004). For example, between 1973 and 1978, oil spills in the Chesapeake Bay Region were estimated to have killed 40,000 birds and of these individuals, 76 percent were Horned Grebes and Long-tailed Ducks Clangula hyemalis (Perry et al. 1978). More than 4,000 Horned Grebes were estimated to have been killed by an oil spill in 1976 (Roland et al. 1997). If such large numbers were killed by oiling incidents in the 1970s, it is quite possible that these mass mortality events had population level effects and led to the declines in numbers observed on the BBS and Long Point migration count data during the 1970s and 1980s. It is not known what impact the recent Deepwater Horizon Spill along the Gulf Coast had on Horned Grebes; remarkably only one incident of an oiled Horned Grebe was reported by USFWS.

Horned Grebes were rated as being moderately vulnerable to oiling in the northeastern Pacific (King and Sanger 1979). However, more recent data – from beached bird surveys conducted in the Pacific northwest by COASST (Alaska to California) suggest that Horned Grebes contribute only a small percentage to the total number of beached birds (0.09%, n = 36: COASST 2014). On the British Columbia Coast, relatively few Horned Grebes are counted during Beached Bird Surveys (K. Barry, pers. comm. 2014), and the frequency of oiling of birds of all species has declined since the 1980s.

However, while beached bird surveys are extremely valuable, caution must be used in using them to estimate mortality from oiling events (see O'Hara and Morgan 2006). For example, compared to Newfoundland and Labrador where 63 percent of beached bird carcases were oiled (Wiese 2003), only 12 percent were oiled in British Columbia (Burger 2002). With the new and increased frequency of oil shipping along the British Columbia Coast, oiling may well become a greater threat to the Horned Grebe.

Horned Grebes are susceptible to oiling in their European wintering range since large aggregations of birds occur there. In North America, the wintering range is more extensive and grebes are more scattered and are thus perhaps less vulnerable to catastrophic oiling incidents (Stedman 2000).

Unsustainable use:

Fisheries by-catch is a global issue for many waterbird species. The extent of this problem for Horned Grebes is currently unknown. Horned Grebes are known to be susceptible to fisheries by-catch and many are drowned in nets on the Great Lakes and other inland waterbodies, as well as at sea. Horned Grebe is listed as one of seven species where by-catch is thought to be a major threat by the Southeast United States Waterbird Conservation Plan (Hunter et al. 2006).

In Europe the threat of by-catch may not be as high; a recent analysis of studies from the North Sea and Baltic Sea indicated that by-catch for the Horned Grebe (Slavonian Grebe) was relatively small and numbered only in the tens of individuals affected (Žydelis et al. 2009). Other incidental catch includes a small number of birds that are shot mistakenly for waterfowl by hunters (Environment Canada 2013).

Climate change:

Because their breeding habitat is dependent on water depth and extent and specific habitat conditions, Horned Grebes may be susceptible to global warming trends (NABCI 2012). The frequency of drought as a consequence of climate warming is predicted to increase within the core range of the Horned Grebe in the Canadian prairies (IPCC 2012) and potentially impact waterbirds (see Steen and Powell 2012). These droughts are predicted to reduce the extent and depth of wetlands, as well as cause extensive drying out of ephemeral wetlands.

In the areas where breeding has been recorded in northwestern Ontario, climate models predict that average temperatures will rise by 5° C by 2071 (Colombo et al. 2007). These warming trends may have several direct and indirect impacts on Horned Grebes. First, wetland area and water levels through the breeding season may decline through increased evapotranspiration.

Second, this could influence aquatic water quality and food supply for Horned Grebes. Third, increases in the length of the growing season as a result of warmer temperatures are predicted to spur an increase in crop production. This could provide increased economic incentive to drain existing wetlands for agricultural production.

Many aspects of the life history of birds, including their survivorship, recruitment, productivity, population dynamics and timing of migration are influenced by climate change and oscillations, including the North Atlantic Oscillation and El Niño Oscillation (Favero and Becker 2006). These can influence temperature, precipitation, storm tracks, and jet stream location and intensity over huge areas (Plummer and Nott 2002). The effects of these oscillations on Horned Grebes are unknown but they could influence breeding distribution and abundance, as well as timing of migration and other factors.

Invasive species:

Invasive plant species such as Reed Canary Grass (Phalaris arundinacea), Common Reed (Phragmites australis ssp. australis) and Purple Loosestrife (Lythrum salicaria) could affect vegetation structure of wetland areas where Horned Grebes nest. These species also compete with native plant species and can dry out wetlands, which could impact habitat quality for Horned Grebes and other wetland-associated species (see Catling and Mitrow 2009, Timmermans et al. 2008). European Common Reed has already reached parts of north-western Ontario (Catling and Mitrow 2009) where Horned Grebes occasionally breed. It is possible that with climate warming, the impact of this species may be even greater, with further drying out of wetlands.

Population growth:

Although Horned Grebes are sensitive to human disturbance in Europe, the effects of this in North America are not well studied. In Scotland, Summers et al. (2009) found that Horned Grebes were disturbed by bank anglers and other recreational use of lochs.

4.0 Management

4.1 Management goal and objectives

The management goal for the Horned Grebe is to enhance and improve the status and viability of the species in Ontario. To reach this goal a set of objectives have been determined with measurable, time-defined approaches that require the support and cooperation of a number of stakeholders. Among the key management objectives are identifying important wetlands used for staging, migration and potential breeding, clarifying the main threats to Horned Grebes, developing Best Management Practices to reduce threats and restore wetland habitat and the development of protocols to accurately assess the current status and range of the species in Ontario.

Understanding the threats to this species involve determining cumulative effects of pollution, climate change, invasive species, and increased human recreational activities on habitat quality and amount.

Table 1. Management objectives for the Horned Grebe in Ontario

No.Management objective
1Determine the distribution and abundance of breeding Horned Grebes in Ontario; identify migration stopover and wintering areas for Horned Grebe in Ontario.
2Determine local and landscape level habitat requirements for Horned Grebe in Ontario.
3Identify the main threats to the Horned Grebe (initially using the IUCN threats calculator and expert opinion); assess methods for mitigating winter mortality from oil spills and by-catch (fishing nets).
4Through a multispecies approach, that includes the Horned Grebe and other wetland species, maintain or expand existing wetland habitat, as well as restore or create new wetlands.
5Develop landowner agreements and management activities to secure, protect, enhance, and restore potential wetland habitats for Horned Grebes and other wetland species.
6Encourage Aboriginal communities to develop stewardship projects and activities that involve species at risk and especially the Horned Grebe.

4.2 Management actions completed or underway

Horned Grebes are protected by the Migratory Birds Convention Act (1994) and are on Schedule 1 of the Species at Risk Act (2003); they are also protected provincially under the Endangered Species Act in Ontario (ESA 2007).

4.3 Management plan approaches for action

Table 2. Management plan approaches for action for the Horned Grebe in Ontario

1. Determine the distribution and abundance of breeding Horned Grebes in Ontario; Identify migration stopover and wintering areas for Horned Grebe in Ontario

Management themeManagement approachRelative priorityThreats or knowledge gaps addressedRelative timeframe
Research Monitoring and AssessmentConduct extensive surveys in areas not well covered by other programs to determine overall population size using adapted CWS Waterfowl Breeding and Habitat Population Surveys or expansion of Marsh Monitoring ProgramNecessary
  • Uncertainty regarding total breeding population in Ontario

2. Determine local and landscape level habitat requirements for Horned Grebe in Ontario

Management themeManagement approachRelative priorityThreats or knowledge gaps addressedRelative timeframe
ResearchDetermine potential habitat in northwestern and southwestern Ontario using habitat suitability models from western provinces (Manitoba)Beneficial
  • Habitat loss
  • Local and landscape habitat requirements
  • All threats
ResearchAddress research needs to more fully understand factors involved in breeding site selection and site fidelityNecessary
  • Habitat loss
  • All threats
Monitoring and assessmentIdentify migration stopover and wintering areas for Horned Grebes in Ontario (using geolocators, satellite radio-telemetry or other platforms such as Motus)Necessary
  • Knowledge gap
Monitoring and assessmentAssess potential contribution of migration counts for determining trends in numbersBeneficial
  • Population status

3. Identify the main threats to the Horned Grebe

Management themeManagement approachRelative priorityThreats or knowledge gaps addressedRelative timeframe
Monitoring and assessmentUse expert opinion and IUCN threats calculator to identify main threats to Horned GrebeCritical
  • All threats
Inventory and monitoringMonitor known breeding and migration stopover sites and investigate threats such as changes in habitat quality, water level control mechanisms, predation, invasive species and human disturbanceNecessary
  • All threats
Long-term Ongoing
ResearchAssess the numbers of Horned Grebes killed by Type E Botulism in Great Lakes (USGS and CWHC)Necessary
  • Threats on staging and wintering areas
Long-term Ongoing
ResearchCollate information on by-catch during the wintering periodBeneficial
  • Unsustain able use
ResearchCollate information on oiling incidents through Beached Bird Surveys involving Horned Grebe – liaise with other jurisdictionsBeneficial
  • Threats on wintering areas

4. Maintain or expand the breeding distribution of Horned Grebe in Ontario by protecting and enhancing existing wetland habitat, restoring wetlands, or creating new wetlands

Management themeManagement approachRelative priorityThreats or knowledge gaps addressedRelative timeframe
ManagementExplore potential for encouraging Horned Grebes to nest in Ontario, through management of water levels, or wetland restorationBeneficial
  • Habitat loss

5. Develop landowner agreements and management activities to secure, protect, enhance, and restore potential wetland habitats for Horned Grebes

Management themeManagement approachRelative priorityThreats or knowledge gaps addressedRelative timeframe
CommunicationsFoster collaboration between agencies such as Ontario Ministry of Natural Resources and Forestry, Environment Canada, and non- government organizations such as Bird Studies Canada, Ducks Unlimited Canada and scientific community to implement protection of breeding and staging areasCritical
  • All threats
Education and outreachLiaise and establish partnerships with other governments, landowners, conservation authori- ties, cottager associations and First Nations to facilitate Best Management Practices that are compatible with the needs of the Horned Grebe and other wetland species (i.e. a multi-species approach) on their landsCritical
  • All threats

Supporting narrative:

Relatively little is known about Horned Grebes in Ontario and the main challenge is that the Western population is on the edge of its range in the province. The most critical objective therefore is to more accurately determine areas used for staging and migration and the breeding distribution and abundance of the species. Setting up a survey specifically for Horned Grebes may be hard to justify or finance, but adapting existing surveys is entirely feasible. It is recom- mended that the modified protocols for the Waterfowl Breeding and Habitat Survey be used in northwestern Ontario (Conway and Gibbs 2005, Routhier 2012, Routhier et al. 2013). This would more completely and accurately describe the distribution and abundance of the species.

Once this has been done, it is recommended that habitat suitability models be developed using data from Ontario and Manitoba to determine the local and landscape level factors influencing Horned Grebe occupancy and breeding success. This would involve GIS mapping of wetland attributes and adjacent land cover, as well as local habitat (wetland size, water quality, vegetation interspersion; see Quesnelle et al. 2013). It is particularly important to identify the key features of wetlands that attract breeding Horned Grebes. Time-lapse photography (see Perkins et al. 2013) could be used to determine the fate of nests. Similar habitat models could be conducted for sites used for staging and migration in Ontario.

It is important that there is collaboration and cooperation among agencies and landowners to protect sites where Horned Grebes are found breeding, as well as other suitable wetlands. This involves working with sewage lagoon managers to maintain existing management regimes or ones that are favourable to Horned Grebes. Although sewage lagoons are apparently attractive to Horned Grebes, the possibility exists that such breeding sites are sinks and that individuals that breed there are bioaccumulating organochlorine pesticides, PCBs and metals (see Hothem et al. 2006 for other avian examples). Best practices could be encouraged and implemented by landowners managing land adjacent to wetland water bodies to minimize agricultural run-off.

Identifying wetlands used by Horned Grebes for staging and migration is also a key management objective. To begin this process, IBAs used by Horned Grebes could be listed (see Zeran et al. 2011 draft).

Horned Grebes appear to adapt readily to human-made ponds so there is considerable potential for wetland restoration (see Locky et al. 2005, Kuczynski, and Paszkowski. 2011). For example, in the second Ontario Breeding Bird Atlas they were recorded nesting in the Rainy River sewage lagoons. Certain types of water regimes at these lagoons may benefit Horned Grebes, whereas others may be detrimental. Changes in the management regime at the sewage lagoons which could influence water levels may determine whether or not habitat is suitable for Horned Grebes (J. Van den Broeck, pers. comm. 2014).

Extrapolating from recent studies in the Prairie Potholes, though in very different landscapes, suggests that grebes may have a metapopulation structure. Routhier (2012) found that occupancy and productivity of breeding grebes was higher in landscapes with greater wetland density and suggested that source-sink dynamics may operate. In terms of management implications, this suggests that conservation efforts for Horned Grebes should focus on maintaining wetland quality in landscapes where grebes breed in higher densities.

Little is known about the specific migration routes and wintering areas of Ontario Horned Grebes. Attaching satellite radio-transmitters or geolocators to some individual grebes from northwestern Ontario and Manitoba would allow these to be ascertained. Radiotelemetry has recently been used successfully for Eared Grebes (Roberts et al. 2013).

Once more information is available on breeding areas, migration routes and wintering areas, specific threats during the annual cycle need to be identified and prioritized. A first step is to use the IUCN threats calculator and solicit expert opinion. A second step is to determine the significance of factors such as by-catch and oiling incidents on Horned Grebe population viability. Collaboration among organizations and personnel working on mitigation to reduce the impact of spills (Ronconi et al. 2004) would be beneficial for the management of the Horned Grebe in Ontario and elsewhere in its range.

5.0 Glossary

Benthic: Organisms associated with the bottom substrate of aquatic environments such as lakes and rivers.

Committee on the Status of Endangered Wildlife in Canada (COSEWIC): The committee responsible for assessing and classifying species at risk in Canada.

Conservation status rank: A rank assigned to a species or ecological community that primarily conveys the degree of rarity of the species or community at the global (G), national (N) or subnational (S) level. These ranks, termed G-rank, N-rank and S-rank, are not legal designations. The conservation status of a species or ecosystem is designated by a number from 1 to 5, preceded by the letter G, N or S reflecting the appropriate geographic scale of the assessment. The numbers mean the following:

1 = critically imperilled
2 = imperilled
3 = vulnerable
4 = apparently secure
5 = secure

Endangered Species Act, 2007 (ESA): The provincial legislation that provides protection to species at risk in Ontario.

Eutrophication: The response of an ecosystem to the addition of natural or artificial substances such as fertilizers or sewage to an aquatic system.

Hemi-marsh: The structure of a freshwater marsh where the proportion of emergent vegetation (e.g., Cattails, Rushes) is equal in proportion (50:50) to open water.

Holarctic: the ecozones of the Northern Hemisphere, includes North America, Asia and Europe. Marsh Monitoring Program (MMP): A volunteer-based program managed by Bird Studies Canada since 1995 where observers annually sample wetlands for breeding birds and calling amphibians to detect trends in populations.

Organochlorines: a carbon based pesticide compound that contains chlorine. These chemicals are known for their negative effects on reproduction in birds of prey and some waterbirds.

Species at Risk Act (SARA): The federal legislation that provides protection to species at risk in Canada. This act establishes Schedule 1 as the legal list of wildlife species at risk to which the SARA provisions apply. Schedules 2 and 3 contain lists of species that at the time the Act came into force needed to be reassessed. After species on Schedule 2 and 3 are reassessed and found to be at risk, they undergo the SARA listing process to be included in Schedule 1.

Species at Risk in Ontario (SARO) List: The regulation made under section 7 of the Endangered Species Act, 2007 that provides the official status classification of species at risk in Ontario. This list was first published in 2004 as a policy and became a regulation in 2008.

Source-sink dynamics: a model of habitat use where one patch of habitat is considered the source and another is considered the sink. The source patch is high-quality habitat where a population of an organism tends to increase. The sink patch is low-quality and cannot sustain a population on its own. The source patch can sustain a sink patch if an excess of individuals moves to the sink patch from the source patch.

6.0 References

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