2005 miscellany (6 January 2006)

Most of the webpages in 'the bird in the hand' are composed to illustrate particular points about ageing and sexing, but we cannot often catch birds according to a programme, and some images do not fit any particular theme. Some are collected here for interest. When noting the plumage details, it is of course important to know the date, so this is given for every photograph.

Little Grebe Tachybaptus ruficollis was an unusual capture in a mist-net at night at Woolston on 2 September 2005. Only some 20 or 30 a year, on average, are ringed in the UK, and this bird was only the 16th ever ringed by Merseyside Ringing Group in its 50-year history. They are not easy birds to age, partly because we are unfamiliar with the species in the hand, and partly because it appears that they rapidly undertake their post-juvenile moult. In fact this is a first-year bird. Its plumage appears to be indistinguishable from that of an adult, but the dull brown iris colour is diagnostic; the iris of adults is red.

Their tarsi are laterally flattened, making them streamlined while swimming. The hind toe is very small, and the lobed feet are adapted for their aquatic habitat:

Another species with unusual feet is the Swift Apus apus: indeed its scientific name 'apus' literally means 'no foot'. Apart from when coming to breeding sites, they spend almost all of their life on the wing. All four toes can face forwards - the arrangement known as pamprodactyl - and they have very sharp claws and short legs, perfectly adapted for clinging on to vertical faces of buildings or trees. Swifts can swivel their outer toes, however, and are well able to grip objects, such as ringers' fingers!

One of the less pleasant aspects of handling Swifts is that they host what are probably the largest flat-flies, relative to the size of bird, of any British species. The infestation seems to vary greatly from year to year: sometimes Swifts are almost free of the parasites and in other years there can be ten or more on some birds. The image below shows one of the hippoboscid flat-flies alongside a rule marked with the small divisions as 1mm.

This fly, Crataerina pallida, appears to be unique to Swift Apus apus. The one depicted above is partially engorged from feeding on the bird's blood.

As mentioned in the previous discussion of Swifts on these pages, some birds miss moulting their outermost primary in some years. These images, taken on 17 July 2005, show two such birds, at left and right, with a normally moulted wing in the centre.

Most birds either breed or moult or migrate. Their body chemistry, especially the hormonal balance, and the differing energy needs of those different activities mean that they are usually separated in time. Some species, however, mostly the larger ones, are able to overlap breeding and moulting. An example previously given was the female Kestrel starting to moult whilst incubating her clutch of eggs. This is also normal for Stock Doves Columba oenas: this adult bird in a nest-box in Delamere Forest on 17 July 2005 had its primary moult at the stage of 5³4¹0⁶.

This bird was very unusual in being in a nest-box with one chick and three warm eggs. The normal clutch for Stock Dove is one or two eggs, although we have recorded occasional broods of 3 chicks. This apparent clutch of four eggs was presumably the result of 'egg-dumping' by a second female.

When the box was re-visited eight days later, the single chick was just old enough to be ringed and the three eggs were cold.

A Willow Warbler Phylloscopus trochilus caught on 23 July 2005 aroused comment because it was an exceptionally yellow bird:

This is clearly a juvenile bird, and the 'loose' texture of the typical juvenile plumage is obvious in this photograph.

Another first-year Willow Warbler showed an abnormality during the growth of its tail:

The study is continuing of eccentric post-juvenile moult in finches. Four Greenfinches Carduelis chloris were caught at north Cheshire sites in August 2005 whilst undergoing active moult of the primaries. In each case the greater coverts had all been moulted, but no primary coverts. It seemed as if the moult was a two-stage process, primary moult starting after the completion, or near-completion, of a 'standard' post-juvenile moult of the coverts.

The first two birds below, a male in my Sutton Weaver garden on 16 August 2005 and a female at Oxmoor Local Nature Reserve on 31 August 2005 respectively, are both actively moulting p5 and p6.

The next bird, ringed on 23 August in my garden, is not as obvious as this female has just dropped p6: note the gap between p5 and p7.

These three birds were moulting symmetrically on both wings. The fourth moulting first-year Greenfinch was moulting p6 on its right wing only when caught at Woolston on 26 August 2005, in the evening when it was too dark to photograph satisfactorily.

A Wren Troglodytes troglodytes on 10 September 2005 posed perfectly, its characteristic cocked tail displaying the white spotting on its undertail coverts. This is a first-year bird, Euring age 3, as seen from the 5 old greater coverts. After the post-juvenile moult, the undertail coverts of first-years and adult appear the same as they are among the tracts of feathers that juveniles replace.

Readers of these webpages with a keen memory will recall the Nuthatch Sitta europaea with a deformed bill that was ringed and retrapped during winter 2004/05. It was a pleasant surprise to retrap him at the same site on 28 December 2005, almost a year after his last capture on 9 January 2005. His bill appears to have grown somewhat more, but the bird is obviously able to survive despite what would appear to be a significant handicap.

David Norman.