DURING a week when Shetland was plunged into sub-zero temperatures and bitter, northerly, snow-bearing winds, it is not surprising that Arctic gulls should feature prominently in the bird records.
On the 22nd a first winter ivory gull, a rare Arctic vagrant, was recorded at Seafield in Lerwick. An ivory gull is about the size of a common gull, the adults being snowy white with a dark grey, yellow-tipped bill and black legs. First year birds are white, with fine black spots and dusky feathering on the face.
Most ivory gulls are seen after strong northerly gales as their wintering grounds are on the edge of the Arctic ice pack. Vagrant ivory gulls are often attracted by the carcasses of seals and cetaceans, as in Bobby Tulloch’s classic transparency of an adult ivory gull feeding on a killer whale carcass in Yell in 1980.
As well as scavenging, these gulls also feed by dipping into the surface layer of the sea, rather like terns. Their flight and calls are also tern-like.
The ivory gull was first added to the British List in 1822 from a specimen shot by Laurence Edmonston of Unst. He also added glaucous and Iceland gull to the list around the same time, by providing specimens.
Glaucous gulls were at Lerwick, Scalloway and Virkie this week, while there were Iceland gulls at Lerwick, Scalloway, Grutness and Sumburgh. Both species are scarce passage migrants and winter visitors from Arctic and sub-Arctic regions.
Unlike the resident herring and great black-backed gulls, these gulls have pure white primary feathers at all stages of their plumage. The adults have pale grey mantles and white underparts with the upper breast streaked brown while the immature are pale brownish or brownish-grey and have no dark band on the tail.
The glaucous gull is larger than a herring gull, with a large head and bill. The sloping forehead and small eyes with yellow eye rings give it a fierce expression.
First winter birds are a pale coffee colour with fine mottling and have pale pink bills with a black tip. Gulls in their second winter have more white in their plumage.
Iceland gulls are smaller than glaucous, about the same size as a herring gull but shorter-legged. At rest, the wing tips project more than the length of the bill beyond the tail. The head is more round than that of the glaucous and the expression is milder.
On the 23rd there was a flock of 40 long-tailed duck in the West Voe of Sumburgh. These attractive winter visitors from the Arctic swim high in the water and dive frequently. They feed on crustaceans, molluscs and other invertebrates. Before diving, long-tailed ducks throw back their heads, spread out their tails and flick their wings. Their Shetland name calloo derives from their onomatopoeic calls.
There were still a few waxwings around this week along with records of chiffchaffs, robins, a song thrush, a mistle thrush, chaffinch, woodcock, brambling, jack snipe and a water rail.
Our garden visitors over the weekend included a rook, a robin, and a chaffinch, as well as rock dove, house sparrow, blackbirds and starlings. In wintry weather, feeding the birds provides them with maximum nutrition for minimum foraging time, and can be a lifeline in severe conditions.