Family Grebes (Podicipedidae)

Vulnerable

Horned Grebe (Podiceps auritus)

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Taxonomy

French: Grèbe esclavon German: Ohrentaucher Spanish: Zampullín cuellirrojo
Other common names: Slavonian Grebe
Taxonomy:

Colymbus auritus

Linnaeus

, 1758,

Europe and America; restricted to Vaasa, Finland

.

Sometimes placed in genus Dytes, although actually closer to P. grisegena and P. cristatus than to other Podiceps. Has hybridized with P. cristatus in C England#R. Subspecific differences slight and partly clinal, and species sometimes considered monotypic. Two subspecies normally recognized.

Subspecies and Distribution
  • P. a. auritus (Linnaeus, 1758) – Palearctic, from Iceland and Baltic to Kamchatka; winters from North Sea to Caspian and off Japan and China.
  • P. a. cornutus (J. F. Gmelin, 1789) – C Alaska to C Canada and NW & NC USA, with isolated population in Quebec (Magdalen Is); winters from Aleutian Is S to California and from Nova Scotia S to Texas.
  • Descriptive notes

    31–38 cm; 300–470 g. Nominate race in breeding plumage Another close view An adult settling on nest has blackish cap, hindneck and upperparts; upperwing blackish brown to brown-grey, with large white panel over most of secondaries, usually a smaller white patch at base of leading edge (on marginal and inner lesser coverts); lores warm brown, becoming conspicuous broad golden band over and behind eye, and broadening as elongated and erectile feathers on sides of rear head, contrasting blackish lower face (including chin and throat) and well-developped tippets; chestnut to maroon-chestnut foreneck and sides of neck, breast-sides and flanks, white abdomen; underwing has pale greyish primaries, dark tertials, otherwise white; iris red, with narrow whitish inner ring; bill black, with whitish tip and small pale area at base of mandible; pink or red line of bare skin from gape to eye; legs dark grey and olive, toes edged yellow. Non-breeding adult Typical non-breeding adult has greyish-black cap to just below eye, lores diffusely pale, narrow dark band along central nape, which broadens on hindneck to grey or brown-grey sides of neck, sometimes extending across upper foreneck; upperparts dark slate-grey, upperwing much as in breeding plumage; lower face, chin, throat and sides of upper neck white, with white of face rather sharply demarcated from dark cap; breast-sides strongly tinged dark grey, becoming more mixed with whitish on flanks, white on central breast and rest of underparts; bill dark grey, rather than black, with larger pale area at tip and, especially, at base. Differs in non-breeding plumage from similar P. nigricollis in having almost all-white ear-coverts, heavier and straighter bill, flat crown, usually some white on forewing, and white on rear wing not extending to inner primaries. Sexes similar. Juvenile Close view of juvenile resembles non-breeding adult, but dark cap and whitish face less clearly demarcated, and has dusky band over ear-coverts. Race cornutus Nearctic race on pond Winter-plumaged bird in California Winter-plumaged bird with fish very similar to nominate, and differences probably not constant, but tends to have paler tuft on sides of head, and in non-breeding plumage is greyer above (especially on crown), while grey fringes to dorsal feathers are broader.

    Drawing by Lluís Solé
    Descriptive notes:

    31–38 cm; 300–470 g. Nominate race in breeding plumage Another close view An adult settling on nest has blackish cap, hindneck and upperparts; upperwing blackish brown to brown-grey, with large white panel over most of secondaries, usually a smaller white patch at base of leading edge (on marginal and inner lesser coverts); lores warm brown, becoming conspicuous broad golden band over and behind eye, and broadening as elongated and erectile feathers on sides of rear head, contrasting blackish lower face (including chin and throat) and well-developped tippets; chestnut to maroon-chestnut foreneck and sides of neck, breast-sides and flanks, white abdomen; underwing has pale greyish primaries, dark tertials, otherwise white; iris red, with narrow whitish inner ring; bill black, with whitish tip and small pale area at base of mandible; pink or red line of bare skin from gape to eye; legs dark grey and olive, toes edged yellow. Non-breeding adult Typical non-breeding adult has greyish-black cap to just below eye, lores diffusely pale, narrow dark band along central nape, which broadens on hindneck to grey or brown-grey sides of neck, sometimes extending across upper foreneck; upperparts dark slate-grey, upperwing much as in breeding plumage; lower face, chin, throat and sides of upper neck white, with white of face rather sharply demarcated from dark cap; breast-sides strongly tinged dark grey, becoming more mixed with whitish on flanks, white on central breast and rest of underparts; bill dark grey, rather than black, with larger pale area at tip and, especially, at base. Differs in non-breeding plumage from similar P. nigricollis in having almost all-white ear-coverts, heavier and straighter bill, flat crown, usually some white on forewing, and white on rear wing not extending to inner primaries. Sexes similar. Juvenile Close view of juvenile resembles non-breeding adult, but dark cap and whitish face less clearly demarcated, and has dusky band over ear-coverts. Race cornutus Nearctic race on pond Winter-plumaged bird in California Winter-plumaged bird with fish very similar to nominate, and differences probably not constant, but tends to have paler tuft on sides of head, and in non-breeding plumage is greyer above (especially on crown), while grey fringes to dorsal feathers are broader.

    Voice

    Commonest call a hoarse rattling “hee-arrr” on descending scale. In display emits a loud pulsating trill of whinnying and fast giggle-like notes terminating with a drawn-out note. Generally silent outside breeding season.

    Habitat

    Breeds on fresh water, occupying small pools and marshes with patches of open water, or secluded sectors of large lakes and rivers. In winter mostly marine, occurring in sheltered bays and occasionally on open sea; also on fresh waters, especially on large lakes and river systems, in S of breeding range. In study of micro-habitats used by present species, Podilymbus podiceps and American Coot (Fulica americana) breeding in aspen parkland near Minnedosa, in Manitoba (Canada), from 1982 to 1984, coots generally occupied shallow-water sites with tall vegetation, present species used deeper water with little vegetation, and both preferred sites with little spatial complexity, whereas Podilymbus podiceps occupied sites intermediate between those of the other two in water depth and vegetation height and favoured more spatially heterogeneous sites; despite annual variation in micro-habitats due to fluctuating water levels, niche occupancy remained relatively constant, coots and present species always being most different from each other, and coots and Podilymbus podiceps always most similar to each other, in micro-habitat use#R. In non-breeding quarters on sea coasts much prefers shallow waters; in German Baltic, non-breeding visitors found mainly in Pommersche Bucht (Bay of Pomerania), where strongly concentrated in shallow-water area of the Oderbank (less than 10 m deep) and in adjacent regions with water less than 20 m deep#R.

    Food and feeding

    Arthropods normally predominate in terms of number, but fish the main food in terms of weight. Highly adaptable, shifting to whatever food readily available: at autumn migration staging areas on Mono L and Great Salt L, in USA, more than 90% of diet composed of brine-shrimps. Arthropods include adults and larvae of insects, especially beetles (Coleoptera), dragonflies and damselflies (Odonata), mayflies (Ephemeroptera), water bugs and caddis flies (Trichoptera), and crustaceans, mainly cladocerans, amphipods and decapods; some molluscs and worms also taken. Fish usually more important in winter, at sea, where crustaceans also taken. Remarkably agile under water, swimming at speed of 1 m/second; this enables capture of sizeable fish. Main foraging method is diving, most dives c. 20 seconds in duration; feeds also from surface, taking floating and aerial prey, or snatching it off aquatic vegetation. Solitary and in pairs; also in small to moderate-sized groups, and occasionally larger flocks (up to several hundreds of individuals), outside breeding season.

    Breeding

    Laying generally Apr–Aug (peak in Jun) in much of range, to Sept in N (e.g. Iceland and Norway); one brood, rarely two. Usually solitary, sometimes loosely colonial. Co-operative breeding recorded very rarely, young of first brood helping to feed second brood. Nest a platform of aquatic plants, usually floating and anchored to vegetation, but sometimes built up from lake bottom or on rocks at water level. Clutch 1–8 eggs, normally 4-5 in Europe, 5–7 in North America; incubation period 22–25 days; downy chicks have white head and neck with blackish longitudinal stripes, upperparts dark grey with ill-defined paler grey stripes and spots, underparts white; fledging period 45–60 days. Sexual maturity probably at 1 year of age. Major study in Iceland gave 63% hatching success, 53% of chicks surviving for 20 days, after which pre-fledging losses minimal; success appears to vary considerably between years; in S Canada (Manitoba) 30·3 of hatchlings fledged, 72% of chicks survived for at least 10 days, mean annual productivity 2·75 young per pair; second broods rarely reach fledging stage.

    Movements

    Migratory. After breeding, moves S to coastal inshore waters, and to lesser extent large lakes. Some populations dispersive, moving only to nearby seas. Overland migration by night, at least in North America; coastal migration often diurnal. In German Baltic, large autumn influx into Bay of Pomerania from Oct, with concentration in Oderbank area, majority remaining in same area in winter; from Mar numbers in Bay of Pomerania decrease markedly s migrants depart#R. In W Europe winters in coastal waters chiefly off Norway, in the North Sea and in the Baltic but scarce further south;  300–400 winter in France, mainly on Atlantic coasts south to Charente-Maritime, although some occur inland and in the south, including Camargue#R. Small numbers winter on northern Spanish coasts, more rarely off Mediterranean Spain, but there are only two accepted records from Portugal#R. Some stragglers, especially to S, with records from Bermuda and Hawaii; also Madeira, Azores, Tunisia and Israel. Rare vagrant in N Indian Subcontinent#R

    Status and conservation

    VULNERABLE. Uncommon to locally fairly common; declining throughout much of range. Estimated global population in range 238,800–582,800 individuals#R#R. European population 6400–9200 pairs in 2005–2014, declining significantly#R. In 1970s, in Europe (nominate race), estimated 500–750 pairs in Iceland, c. 500 pairs in Norway, c. 25,000 pairs in Sweden and c. 500 pairs in Estonia; in Finland, c. 3000 pairs in 1958. Numbers in Iceland dropped to 400 by c. 1990, thereafter increasing to 700 pairs in 2005#R, while Swedish population fell to 1200 pairs by end of 20th century and 50–100 by 2008–2012#R; Finland retained 1500–3300 pairs in 2006–2012, while Norway harboured 750–850 pairs in 2007#R. First recorded breeding in Scotland in 1908, with increase to maximum of 81 pairs in 1984, since when steady decline to 61–62 pairs in 1987, and 23 pairs in 2009#R; has bred in England#R. In the past may have had a much wider distribution in NW Europe, but acidification and increased humus content of lakes probably led to range contraction; man-induced eutrophication of lakes permitted general expansion during 20th century, but species appears currently to be declining in many places, additional problems resulting from accidental bycatch in fishing nets; in some places, e.g. Scotland, afforestation known to be responsible for loss of several pairs, as it causes hydrological changes leading to reduced quantities of invertebrates. New data from across Europe for the European Red List of Birds indicate that the European population has declined overall by 25–30% over the last three generations (21·3 years). Consequently, the species is now classified as Near Threatened at European level#R. Widespread but apparently uncommon throughout its Asian range, where much less studied; population trends unknown. Numbers in North America (race cornutus) uncertain#R, and one estimate of 100,000 pairs perhaps over-optimistic. Figures from Breeding Bird Survey and Christmas Bird Count indicate a large and statistically significant decrease since 1970s in North America, with a decline of 75·9% over 40 years (equating to 29·9% per decade)#R#R; American breeding range has contracted considerably, formerly reaching S and E to N Utah, N Indiana and S New England, and species is apparently still declining. Main threats in Nearctic believed to include human disturbance, forestry operations around breeding lakes, fluctuating water levels, and stocking of lakes with rainbow trout (Oncorhynchus mykiss), which compete with grebes for aquatic insects. Particularly vulnerable to oil pollution: of 34,717 oiled birds killed in eight spills in S USA, 12·3% were of present species; 8–16% of wintering population of Shetland Is (off N Scotland) killed after oil spill in 1978–1979. Not considered of global conservation concern until 2015, when information about global population declines triggered uplisting to Vulnerable.

    Recommended citation

    Llimona, F., del Hoyo, J., Christie, D.A., Jutglar, F., Garcia, E.F.J., Kirwan, G.M. & Sharpe, C.J. (2017). Horned Grebe (Podiceps auritus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/52490 on 28 July 2017).