Local rarities this week included subalpine warbler, tundra bean goose, white-billed diver and black kite. The subalpine warbler, a fine singing male, was first recorded at Scatness on the 22nd.
Slightly smaller than a common whitethroat, the male in breeding plumage is a colourful bird, with a grey head and mantle, with contrasting brick red on the throat, bordered by bold white moustache stripes. The eye-ring and ring around the eye are also red. Subalpine warblers are rare migrants from southern Europe, breeding in areas around the Mediterranean and wintering in Africa, south of the Sahara.
Records of this species have increased since the late 1980s, with almost 50 per cent being from Fair Isle. Most subalpine warblers occur from early May to mid-June, April records being fewer.
The tundra bean geese, which have been on Mousa recently, are now in Sandwick. A white-billed diver was at the north end of Mousa on the 26th. The black kite flew north west over Sandwick on the evening of the 27th. This species is a very rare vagrant from Europe with only 19 Scottish records (Birds of Scotland 2007) and two records from Shetland, although it is regularly seen in the southern parts of Britain. In 1966 one was recorded at Sumburgh and in 1997 an individual was observed at several locations. Most Scottish records are in spring and are probably overshoots by birds returning to breed on the European continent.
At this time of the year, there is a mix of winter visitors and passage migrants, along with summer breeding visitors. There are still records of Iceland gulls, with five in the Lerwick area on the 23rd.
Turnstones, now in smart tortoiseshell plumage, and purple sandpipers are gathering prior to migrating to their northern breeding grounds. There were 10 purple sandpipers at Leebitton and 29 purple sandpipers at Ness of Sound. Nine whimbrels were at Scatness, possibly returning breeders.
The male wood duck was still at the Loch of Brow on the 26th. At Scatness there was a hybrid tufted x ring-necked duck. The male ring-necked duck is on the Loch of Tingwall. At Spiggie there were two gadwall, two shoveller and a male goosander. Other migrants recorded this week included common tern, osprey, carrion crow, common scoter, black-tailed godwit, hawfinch, chaffinch, greenfinch, brambling, goldfinch, willow warbler, chiffchaff, lesser whitethroat, blackcap, siskin, swallow, house martin, sand martin, dunnock, redwing, fieldfare and ring ouzel.
On the 22nd a large white butterfly was recorded at Scatness, and on the 25th I had a Shetland bumblebee in the garden. This species of bumble bee is readily recognised by its orange thorax, easily visible when it is in flight. White-tailed bumblebees emerge first and are buzzing around in early April, the Shetland bumble bee appearing later. Only the mated females survive the winter and found a new colony. The nest, made of grass and moss with the wax cells in the middle, is often built in a small hole in the ground, like an old mouse hole, or in the base of a tuft of grass.
We had a Shetland bumblebee nest in the garden last year in a large clump of grass so could watch the comings and goings of the residents. Bumblebees are attracted to areas with flowers as they collect nectar and pollen to feed the larvae. The pollen is collected in specially modified pollen baskets on the hind legs.