Podiceps auritus (Linnaeus, 1758)
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Basis for Listing
The Horned Grebe (Podiceps auritus) occurs across the northwestern tier of the United States, from Minnesota to Oregon and northward through most of Canada to central Alaska. Formerly, this species also nested south and east to the Atlantic Coast. Horned Grebes nested throughout much of Minnesota in the early 1900s, though they were more regular and abundant in the northern counties and rare or absent in the southeast. By 1984, breeding records were restricted to the Roseau River Wildlife Management Area and Agassiz National Wildlife Refuge in northwestern Minnesota (Aspen Parklands). This range contraction coupled with declining numbers led to the Horned Grebe's designation as a state special concern species in 1984. A 1991 survey for Horned Grebes in northwestern Minnesota located only one grebe, and there was no evidence of breeding (Boe 1992). Breeding activity was noted at just one location in 1994 and again in 1995. As a result, the Horned Grebe was reclassified as a threatened species in 1996.
Since 1996, reports of Horned Grebes in suitable habitat during the breeding season continue to be scarce, and no persistent breeding populations are known in Minnesota. The only documented nesting in Minnesota in the past 20 years was in 2013 when two pairs, including one pair with several young, were found at Agassiz National Wildlife Refuge. Horned Grebes are a relatively common migrant in the state, and non-breeding individuals are occasionally observed during the summer, though typically not in suitable nesting habitat. In several instances, what appear to be juveniles have been sighted, but these may be immature birds that may have moved into the state after fledging elsewhere. Horned Grebes observed during summer on wastewater treatment ponds are most likely non-breeding individuals as no actual breeding has been confirmed at these sites. Due to the current breeding population size and with continuing threats from habitat loss and water quality issues, in 2013, the status of the Horned Grebe was elevated to endangered.
In breeding plumage, this small water bird is readily identified by its bright red eye, prominent yellow-gold ear tufts, and reddish neck, breast, and flanks. The similar-sized Eared Grebe (Podiceps nigricollis) has sparse yellow cheek patches, a black neck, and pointed crown. Horned and Eared grebes can be more difficult to distinguish in non-breeding plumage. Horned Grebes typically have more extensive white on the cheeks and neck, but these differences can be subtle.
Horned Grebes nest in marshes and on lakes with emergent vegetation. They build floating nests, so on larger lakes they prefer to use bays and inlets that provide protection from wind and wave action. Nests are constructed in shallow water, usually within emergent vegetation. During migration, Horned Grebes can be observed on a variety of lakes, even those without emergent vegetation.
Biology / Life History
Horned Grebes are a fairly common migrant in the state, particularly in the fall when hundreds, and sometimes thousands, can be found on large lakes. The species migrates more than 1,000 km (621 mi.) between summer breeding grounds and coastal marine overwintering sites. Pairing may begin on the wintering grounds and continue during migration. They usually arrive in Minnesota between mid-March and mid-April. Intricate mating displays are performed in the breeding areas. Nesting occurs solitarily, in loose aggregations, or occasionally in small colonies. Each pair defends a territory that is usually less than 1 ha (2.5 ac.) in size. It is common for Horned Grebes to re-nest after failure of a first nest, but successful second broods are rare. Average clutch size in Minnesota is about 5 eggs, and males and females both take part in incubation. Hatching occurs after about 24 days. Although chicks are precocial and able to walk and swim within hours of hatching, they must be fed and warmed by their parents for their first two weeks. During this time, chicks often ride on their parents' backs, even while the parent dives underwater in search of food. The young usually stay on the marsh where they hatched until they are able to fly at 41-50 days. The summer diet of this species consists of aquatic arthropods and small fish. Airborne insects may be seized from the air or skimmed off the surface of the water and eaten as well. In winter, fish and crustaceans make up the majority of the diet (Stedman 2000).
Conservation / Management
Horned Grebes are generally tolerant of humans, though they may abandon lakes with highly developed shorelines or too much human activity on the water. Several serious threats to Horned Grebe habitat in Minnesota are the direct result of agricultural activities including eutrophication of water bodies from fertilizer run-off, pesticide build-up, and filling or draining of wetlands (Stedman 2000). Maintaining and improving the quality and quantity of wetlands in the state will ensure that suitable habitat for Horned Grebes remains available. Several floodwater impoundments have been created in northwestern Minnesota and, if properly designed and managed, may have the potential to provide Horned Grebe nesting habitat.
Conservation Efforts in Minnesota
In 1991, the DNR's Nongame Wildlife Program funded a survey of 76 wetlands deemed to provide suitable Horned Grebe habitat in six northwestern counties (Kittson, Marshall, Pennington, Polk, Red Lake, and Roseau). The survey located only one Horned Grebe at Roseau River Wildlife Management Area and found no evidence of breeding activity (Boe 1992). Breeding season bird inventories by the Minnesota Biological Survey and Nongame Wildlife Program from 1992 to 2008 located Horned Grebes only at the Roseau River, Twin Lakes, and Thief Lake wildlife management areas.
The Minnesota Breeding Bird Atlas (MNBBA 2009-2013) provided an opportunity to assess the breeding status of Horned Grebes and perhaps discover new breeding locations in the state. During the MNBBA, confirmed nesting was documented at only one location: Agassiz National Wildlife Refuge. While encouraging, clearly Horned Grebes remain an extremely rare nesting species in Minnesota. Agassiz National Wildlife Refuge and other large wetland complexes in northwestern Minnesota should continue to be monitored for potential nesting Horned Grebes.
Steven P. Stucker (MNDNR), 2018
(Note: all content ©MNDNR)
References and Additional Information
Boe, J. 1992. A survey for breeding Horned Grebes in Minnesota. Final report submitted to the Nongame Wildlife Program, Minnesota Department of Natural Resources. 34 pp.
Pfannmuller, L., G. Niemi, J. Green, B. Sample, N. Walton, E. Zlonis, T. Brown, A. Bracey, G. Host, J. Reed, K. Rewinkel, and N. Will. 2017. The First Minnesota Breeding Bird Atlas (2009-2013) [web application]. <http://www.mnbba.org/blockmap/species.php?species=Horned%20Grebe>.
Stedman, S. J. 2000. Horned Grebe (Podiceps auritus). Number 505 in A. Poole and F. Gill, editors. The birds of North America. The Birds of North America, Inc., Philadelphia, Pennsylvania.