Black-necked Grebe

The black-necked grebe usually measures between 28 and 34 centimetres (11 and 13 in) in length and weighs 265 to 450 grams (9.3 to 15.9 oz). The bird has a wingspan range of 20.5-21.6 in (52-55 cm). The nominate subspecies in breeding plumage has the head, neck, breast, and upper parts coloured black to blackish brown, with the exception of the ochre-coloured fan of feathers extending behind the eye over the eye-coverts and sides of the nape. This eye is mostly red, with a narrow and paler yellow ring on the inner parts of the eye and an orange-yellow to pinkish-red orbital ring. The thin, upturned bill, on the other hand, is black, and is connected to the eye by a blackish line starting at the gape. Sometimes, the foreneck can be found to be mostly tinged brown. The upperwing is blackish to drab brown in colour and has a white patch formed by the secondaries and part of the inner primaries. The flanks are coloured tawny rufous to maroon-chestnut and have the occasional blackish fleck. The underwing and abdomen is white, with an exception to the former being the dark tertials and the mostly pale grey-brown outer primaries. The legs are a dark greenish grey. The sexes are similar. In non-breeding plumage, the nominate has greyish-black upper parts, cap, nape, and hindneck, with the colour on the upper portion of the latter being contained in a vertical stripe. The dark colour of the cap reaches below the eye and can be seen, diffused, to the ear-coverts. Behind the ear-coverts on the sides of the neck, there are white ovals. The rest of the neck is grey to brownish-grey in colour and has white that varies in amount. The breast is white, and the abdomen is whitish. The flanks are coloured in a mix of blackish-grey with white flecks. The colour of the bill when not breeding differs from that of the breeding plumage, with the former being significantly more grey. The juvenile black-necked grebe is similar to the non-breeding adult. There are differences, however, including the fact that the dark areas are usually more brownish in the juvenile, with less black. The lores are often tinged pale grey, with whitish marks behind the eye. On the sides of the head and upper neck, there is a buffy or tawny tinge. The chick is downy and has a blackish-grey head with stripes and spots that are white or pale buff-grey. The throat and foreneck are largely pale. The upper parts are mostly dark grey in colour, and the abdomen is white. The subspecies californicus usually has a longer bill compared to the nominate, and has brown-grey inner primaries during the breeding season. When not breeding, the nominate has diffuse and pale lores less often than Podiceps nigricollis californicus. The other subspecies, P. n. gurneyi, is the smallest of the three subspecies, in addition to having a greyer head and upper parts. The adult of this subspecies also has a rufous-brown tinge on its lesser wing-coverts. It also lacks a non-breeding plumage, in addition to the tufts on the side of its head being paler.

When breeding is over, the black-necked grebe usually partakes in a moult migration to saline lakes. It especially prefers lakes with large numbers of invertebrate prey, so it can fatten up while moulting and before going on its winter migration. Some birds, although, moult when on the breeding grounds, but most do not moult until the end of the moult migration. This migration is dangerous, with hundreds and sometimes thousands of birds being killed by snowstorms when traveling to places such as Mono Lake. When it finishes its moult migration, this bird moults its remiges between August and September, which makes it unable to fly. This moult is preceded by an increase in weight. During the moult, the breast muscles atrophy. When the moult is completed, this grebe continues to gain weight, often more than doubling its original weight. This additional fat is used to power the black-necked grebe's overnight fall migration to its wintering grounds. The fat is most concentrated in the abdomen, second most in the thorax, and least in the chest. This bird usually starts its migration earlier when shrimp is more abundant and when the moulting lake is at a higher than average temperature. It generally leaves on a clear night with lower than average surface temperatures.