Podiceps auritus (Linnaeus, 1758)
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Basis for Listing
The horned grebe occurs across the northwestern tier of the United States, from Minnesota to Oregon, and northward through most of western Canada to central Alaska. Formerly, this species also existed south and east to the Atlantic Coast. Horned grebes nested throughout Minnesota in the early 1900s, although they were more regular and abundant in the northern counties. By 1984, breeding records were restricted to the Roseau River Wildlife Management Area and Agassiz National Wildlife Refuge in northwestern Minnesota. 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.
This small water bird is readily identified by its bright red eye, yellow-gold ear tufts, and reddish neck, breast, and flanks. In winter, the horned grebe may be confused with the similar-sized eared grebe (Podiceps nigricollis), but the broad, white cheek patches of the horned grebe are absent in the eared grebe. Also, the head of the horned grebe is much flatter in appearance on the top than that of the eared grebe.
Marshes and lakes are the preferred habitat of the horned grebe. The species builds floating nests, so on large water bodies (over 10 ha (24.7 ac.)) they prefer to use bays and inlets, which provide protection from wind and wave action. Nests are constructed in shallow water, usually within emergent vegetation.
Biology / Life History
Horned grebes migrate more than 1,000 km (621 mi.) between summer breeding grounds and coastal marine overwintering sites. They usually arrive in Minnesota between mid-March and mid-April. Pairing may begin on the wintering grounds and continue during migration. Intricate mating displays are performed in the breeding habitat. 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 true second broods are rare. Clutches average 5-7 eggs, and males and females both incubate them. Hatching occurs after about 24 days. Chicks are precocial and able to walk and swim within hours of hatching, but must be fed and warmed by their parents for their first 2 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, although 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.
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 only located horned grebes at the Roseau River, Twin Lakes, and Thief Lake Wildlife Management Areas. Further studies are needed to determine why apparently suitable habitat in the state is not being utilized by horned grebes.
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.
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.