Eared Grebe

A regular breeding species and migrant; the Eared Grebe was a rare species during the Minnesota Breeding Bird Atlas (MNBBA).

Present on every continent except Australia and Antarctica, the North American subspecies (Podiceps nigricollis californicus) is a western bird. Restricted largely to the northern Great Plains of the United States and Canada and to the more arid grasslands farther west, the Eared Grebe reaches the eastern periphery of its breeding range in western Minnesota. Scattered pockets of abundance are found in a few widely dispersed localities (Figure 1).

Assigned a Continental Concern Score of 12/20 by Partners in Flight and ranked as a species of Moderate Concern by the North American Waterbird Conservation Plan; designated a Species of Greatest Conservation Need in Minnesota.

Medium-distance migrant; most birds winter in coastal waters along California.

A diver that forages primarily on a wide variety of aquatic invertebrates, although small fish and frogs may be taken as well.

A loosely constructed platform of aquatic vegetation that may be floating in shallow water or anchored to other vegetation. A colonial nester.

In the early 1900s, Roberts (1932) described the Eared Grebe as a summer resident in the western prairie region of the state, breeding as far east as Hodgson Lake in Renville County, as far south as Swan Lake in Nicollet County, and as far north as eastern Kittson and Marshall Counties. Roberts considered the grebe to be quite abundant in some localities but noted that it was “irregularly distributed.” He observed a colony of 100 or more birds on Heron Lake in Jackson County, nestled within the lake’s legendary Franklin’s Gull colony, and at least 150 birds at another unidentified site in the southwest region. Elsewhere, however, smaller colonies usually supported just 10 to 15 breeding pairs. Despite their broad distribution, confirmed nesting records (nests with eggs) were limited to Jackson, Kittson, Marshall, and Renville Counties. An inferred breeding record (“feeding young”) also was reported from Lyon County. Although the birds were observed at the large wetland complex on Swan Lake for many years, nearly thirty years passed before nesting was confirmed (Huber 1961).

The grebe’s rarity was confirmed more than 40 years later when Green and Janssen (1975) provided an updated account of the species. Its breeding range remained essentially unchanged from Roberts’s earlier description. Confirmed breeding records from 11 counties were restricted largely to the southwestern and south-central regions of the state but also stretched as far north as Kittson and Marshall Counties in the northwest. Most notable was the fact that in the 25 years preceding the publication of their book, Eared Grebes had only been reported nesting at three sites: near the town of Alberta in Stevens County, at Swan Lake in Nicollet County, and at the Agassiz National Wildlife Refuge in Marshall County.

Then, in the late 1970s and early 1980s, the newly established Minnesota Nongame Wildlife Program launched an effort to assess the distribution and abundance of all colonial waterbirds nesting in the state. The project focused on compiling reports from Minnesota Department of Natural Resources field staff working throughout the state and from local and federal natural resource agencies and colleges and universities. Limited field surveys also were conducted. As a result of these efforts, 4 active Eared Grebe colonies were identified in 1977 (Henderson 1977) and 8 in 1980 (Henderson and Hirsch 1980). A 1985 summary report identified a total of 14 colonies that were active at least 1 year between 1981 and 1983 (Guertin and Pfannmuller 1985). Included in these reports were 2 accounts of small colonies located east of the previously documented breeding range: 1 at French Lake in Hennepin County (1980) and 1 in Anoka County (1985).

The increase in the number of colonies was believed to simply reflect new reports of small colonies that had previously gone unreported rather than a true increase in the population. Only 2 of the colonies reported in 1985 included more than 50 breeding pairs. The largest colony, numbering over 100 pairs, was on the Agassiz National Wildlife Refuge in Marshall County. The 1985 publication also noted that in addition to the 14 colonies that were active between 1981 and 1983, 2 new colonies were located on state Wildlife Management Areas (WMAs) in Yellow Medicine County in 1984: Miller Richter WMA (3 nests) and Timm’s Lake WMA (103 nests).

In 1986, a 4-year field study on Minnesota’s Eared Grebe population was launched (Boe 1992; Boe 1993; Boe 1994; Boe and Prahl 1987). Known colony sites were surveyed during the first field season. Of the 27 localities surveyed, Eared Grebes were found at 12 sites, and nesting was confirmed at 9 sites. Three previously unreported colonies also were found, including another site in the metropolitan region in Carver County (Boe and Prahl 1987).

Janssen’s updated account of the species status in 1987 included expanded details on recent nesting occurrences. He identified 16 counties where nesting had been confirmed since 1970, including 2 records farther east in the state: the Carver County record cited above and a new record in Freeborn County in south-central Minnesota. Earlier accounts from the Nongame Wildlife Program of colonies in Anoka and Hennepin Counties were not included. Janssen (1987) speculated the grebe’s use of sewage treatment ponds for nesting might explain some of its eastward range expansion. Although Eared Grebes frequently nest in large colonies in suitable wetland complexes, reports from these eastern sites were invariably of small colonies, usually numbering fewer than 10 pairs.

Fieldwork conducted by the Minnesota Biological Survey also identified a total of 20 breeding-season locations for the species. Most notable was a report from central St. Louis County (Minnesota Department of Natural Resources 2016). With all the new fieldwork under way, by 1998 Hertzel and Janssen identified a total of 30 counties where nesting had been confirmed since the year 1970, including Anoka, Hennepin, and Carver Counties in the greater Twin Cities metropolitan region.

During the MNBBA, Eared Grebes were reported from only 12 atlas blocks, including 7 priority blocks. Breeding evidence was confirmed in 5 blocks (Figures 2 and 3; Table 1). The birds were observed in 10 of Minnesota’s 87 counties, including the St. Louis County report from the Minnesota Biological Survey in 2012. Breeding was confirmed in 4 counties: Grant, Lac qui Parle, Marshall, and Polk. No birds were reported in the Twin Cities metropolitan region. Among the 12 blocks where Eared Grebes were reported, 5 had sewage treatment ponds within the block, including the record for St. Louis County.

Eared Grebes can be a difficult species to survey. Small colonies located in small wetlands or wastewater treatment ponds are usually quite obvious. But colonies, even large ones, nesting in extensive wetland complexes, far from roads or access points, can be particularly challenging and may not have been well accounted for during the MNBBA.

At best, this small grebe remains a rare and elusive member of Minnesota’s wetland bird community. Indeed, the small number of atlas records suggests that the species may have declined over the past 20 to 30 years. Apart from distributional shifts that reflect local changes in habitat, the current distribution of Eared Grebes in North America is remarkably similar to that documented in years past (Cullen et al. 1999).

*Note that the definition of confirmed nesting of a species is different for Breeding Bird Atlas projects, including the definition used by the Minnesota Breeding Bird Atlas, compared with a more restrictive definition used by the Minnesota Ornithologists’ Union. For details see the Data Methods Section.

Besides their use of sewage ponds, the nesting habitats Eared Grebes most commonly select are shallow, prairie wetlands with emergent vegetative cover (Figure 4). In Minnesota wetlands were larger than 30 ha; lacked public access; were shallow, with a maximum depth of 3 m (mean depths at colonies ranged from 50 cm to 114 cm); and had 50%–100% open water (Boe 1992). Sites were characterized by abundant submerged vegetation, abundant emergent cover, or both.

Nests are usually placed within sparsely distributed emergent vegetation and are 0–50 m from open water. The distance from the shore to the colony varies with the size of the wetland; in large wetland complexes the nests are found farther from shore (Boe 1993). Waves caused by high winds are a major cause of low reproductive success and nest abandonment.

Biologists estimated the global population of the Eared Grebe was approximately 3.9 million to 4.1 million birds. Populations outside of North America are small, ranging from 10,000 to 268,000 birds; the population in North America is at least 3.7 million birds (Wetlands International 2015). Systematic surveys of breeding colonies are rare and insufficient to provide census data. However, en route to their coastal wintering grounds, the majority of North American Eared Grebes stop at several saline lakes in the Great Basin, where they undergo a rather remarkable transformation and molt as they gorge on the lakes’ brine shrimp. Aerial censuses conducted at these fall staging areas may provide the best estimate of the population size in North America. A census conducted in these areas in 1997 yielded a fall population estimate of 4.1 million birds (Cullen et al. 1999).  More recently, however, Partners in Flight (2017) has estimated a much smaller global population size of only 2.7 million birds.

The number of birds in Minnesota is unknown, but in 1986, when Boe and Prahl (1987) visited all known colony sites, they reported a total of 238 adults. During the course of Boe’s four-year field study from 1986 to 1989, she documented considerable variability in the number of nesting pairs, ranging from a low of 206 adults in 1987 to a high of 2,672 adults in 1988 (Boe and Prahl 1987; Boe and Nuechterlein 1990).

Given the Eared Grebe’s wetland habitat and very localized distribution, the Federal Breeding Bird Survey (BBS) is limited in its ability to track its populations. Most statistical analyses are compromised due to the species’ low abundance. The only ecological region where these data are sufficient is in the Prairie Pothole Region, which includes all of western Minnesota. Here BBS data reveal a nonsignificant annual increase of 2.04% per year from 1966 to 2015; an even larger increase of 4.12% per year is evident from 2005-2015 (Figure 5). Although they are still relatively uncommon on BBS routes in North Dakota, the data suggest a significant increasing population in the state (Sauer et al. 2017). Eared Grebes are so rare in Minnesota that they are not detected on BBS routes.

Long-term population data are available from the Christmas Bird Count, but these data are skewed by one count that is 12 times higher than the long-term average. When that year is eliminated (1988), these data illustrate a relatively stable population (Figure 6; National Audubon Society 2016). One potential issue with the Christmas Bird Count data is the challenge of distinguishing Horned Grebes from Eared Grebes in their winter plumage, as the winter ranges of the two species overlap along the Pacific coast.

Unfortunately, there is no statistically robust means of assessing long-term population trends of the Eared Grebe. Continued monitoring at fall staging areas in the Great Basin may, if continued, provide the best source of data. In the interim, although global population estimates suggest a major decline, it appears that populations within the northern Great Plains may be stable to increasing in abundance.

In light of its relatively large population and wide distribution, the Eared Grebe has not been the focus of conservation efforts. It is listed by the North American Waterbird Conservation Plan as a species of Moderate Concern (Kushlan et al. 2002) and has been assigned a moderate Continental Concern Score of 12/20 (Partners in Flight 2017).  Concerns include recent population estimates that suggest a significant population decline and threats to its breeding and nonbreeding habitat. Because hundreds of thousands of birds concentrate for months at a limited number of staging areas and wintering sites, the potential for a catastrophic event that negatively impacts the species is high. Cullen et al. (1999), for example, noted the frequent die-offs that have occurred at the Salton Sea in California, one of the largest wintering sites.

It the late 1800s and early 1900s, Eared Grebes were among the colonial waterbirds whose plumage was valued for the millinery trade. And as European settlers converted grassland landscapes to agricultural croplands, the species no doubt experienced further declines due to the widespread loss and degradation of wetlands. Unfortunately these losses continue, and the grebe’s demonstrated preference for large, shallow wetland complexes with minimal disturbance makes it particularly vulnerable. In light of these concerns, the Eared Grebe has been designated a Species of Greatest Conservation Need in Minnesota (Minnesota Department of Natural Resources 2015).

Like all wetland-dependent species, aggressive wetland conservation policies and management to protect and restore sites are critical, particularly in light of the predicted impacts of a warming climate. A recent analysis by the National Audubon Society classified the Eared Grebe as “climate endangered” and predicted that 100% of the species’ current breeding range could be lost by the year 2080 (Langham et al. 2015; National Audubon Society 2017). The future of many wetland species that depend on North America’s interior wetlands is truly at stake unless more aggressive measures are initiated.