The largest and most impressive bird of prey in Britain was recorded this week, when a white-tailed eagle was seen flying over the South Mainland on the 12th. This bird, which was radio- and wing-tagged, originated from a recent introduction programme in eastern Scotland. It had previously been seen at the Loch of Strathbeg in Aberdeenshire and in North Ronaldsay.
The white-tailed eagle, also called the “sea eagle”, is the fourth largest eagle in the world, with a wing span of two and half metres. Its breeding range extends from Japan, through the Middle East and Siberia into Europe.
Sea eagles also bred in Britain until they were persecuted to extinction, the last pair breeding on Skye in 1916 and the last known individual, an albino female, being shot in Shetland in 1918. Erne Stack off Easter Quarff was a sea eagle nest site – “erne” being derived from a Scandinavian word for eagle.
In 1959 (in Glen Etive) and in 1968 (Fair Isle), unsuccessful attempts were made to re-introduce this magnificent bird by bringing over young eagles from Norway. In 1975 the sea eagle re-introduction project restarted in Rhum, with 82 birds being released in the next 10 years. I was fortunate to visit the island and to see these huge birds some years after the initiation of the project. The first successful breeding of introduced sea eagles was in 1985, and, since then, the population of native-born sea eagles has increased. Further introductions have also taken place, returning the sea eagle to its rightful place on the list of Scottish breeding birds.
In contrast, the wren is one of the smallest of our breeding birds. In spring, the males build several domed nests from leaves, moss and other vegetation. Often these nests are made under overhanging banks along the coast, or in dry stone dykes or in dense coverings of ivy. The female chooses one, which is then lined with feathers before the eggs are laid. Two sub-species of wren are found in Shetland: the zetlandicus race and the frideriensis sub-species which occurs in Fair Isle.
April has brought a substantial increase in the number and variety of migrants arriving in Shetland. This week there have been widespread records of common species such as robin, blackcap, chiffchaff, chaffinch, greenfinch, siskin, song thrush and wood pigeon. A goldfinch was at Cunningsburgh, and another at Trondra, on the 10th. Other species included black redstart, stonechat, brambling, willow warbler, linnet, swallow and carrion crow. An osprey was recorded at Urafirth on the 8th, and there was a red-head smew at the Loch of Houlland in South Nesting.
An interesting insect record was the peacock butterfly which was found in a shed at Voe on the 5th. Peacock butterflies are occasional migrants to Shetland. Overwintering as adults, they emerge when the temperatures warm up, and are one of the earliest species on the wing in woodland areas in spring. The large, conspicuous eyespots on each wing are anti-predator devices, designed to frighten off would-be attackers. The undersides of the wings are a dark greyish-black, providing very good camouflage when the butterfly is at rest with its wings folded together.
Joyce J M Garden