Wednesday, February 26, 2014

Black-tailed Godwit at Southend

A Victorian book for bird egg collectors laments that the Black-tail Godwit Limosa limosa (L.) is "unrecorded as nesting in Britain since 1847 nearest nesting ground Iceland" and illustrates the egg on the same plate 16 as the actually extinct Great Auk Alca impennis "existent until 1840" (W. J. Gordon Eggs of British Birds). With a decline of egg collecting and shooting as hobbies, plus conservation of marshland habitats, the Black-tailed Godwit has returned to breed in England and I was able to see one stranded dead at Chester Avenue beach in Southend-on-Sea about 8 hours after the morning neap tide and the usual S.W. wind brought it in on January 24 2014. This bird species has or had a breeding range right around temperate grasslands. Since it also migrates south in winter, there is an interesting report of a skeleton preserved in ice at 4.9 km elevation on Mount Everest (Paul Geroudet 1954, Nos Oiseaux v. 22 p.254). Modern bird books tend not to want to describe them with the measurements required to identify these dead birds and yet it is important to record mortalities like that. I have therefore been trying to learn how to identify the birds seen on the Southend strandline and also record their positions for comparison with the orientations of dinosaurs etc. This particular bird had a remarkably long and straight bill of 100 mm length out of a total 140 mm head and bill length aligned with the bill pointing west on and along the Fucus strandline. The tip of the bill was black and the rest pale pin. Since the bill is made of keratin and originally used to probe soils for invertebrates, rather than conserved intertidal habitats, one can speculate that the black tip is harder and the straight bill less prone to bending or buckling failure than the curved bills Curlews Numenius arquata (L.) which I have seen stranded. May be the curlew uses the bill more like a device to push the grass apart, or in softer ground? Another question is raised by the plumage and dimensions of the rest of my find. It had stranded ventral-up with the wings half-folded and the grey legs and apparently unwebbed feet (the do have small webs however) extended straight south down the beach like the frog described earlier. The length from the top of the head to the tail with a black bar on it was 320 mm and to the tip of the feet 380 mm. The long legs and bill being bare are likely to have hung down more than they do in most birds buoyed by air in the feathers, and so acted like anchors or rudders during standing at a point where the tide moving east against the wind in Thorpe Bay reaches sand and a jetty on the west side blocks the wind. There was a small excavation in the anterior thorax probably made by a crow after stranding. Apart from that the feathers were intact and more brown, apart from the black wing and white bar, and grey areas on the head, than winter plumage illustrations suggest. It was therefore like the North American equivalent species or geographical subspecies the rare Hudsonian Godwit. However, the length when turned over and made straight was 17 inches (c. 430 mm), not the equivalent unstretched 13 inch tip of bill to tip of tail measurement given for the Hudsonian Godwit in Robbins et. al. 1966 Birds of North American, Golden Press N.Y. It seems likely that when retreated into the marshland habitat now favoured by conservation in Europe, the species became smaller in North America during the Ice Age/Ages when grassland was unavailable. It is remarkable how different the present bird fauna of eastern North America is to Eurasia at species or subspecies level and that can hardly be due to the Rocky Mountains when a bird like this can migrate each year over higher mountains to India.

Guillemot at Southend

I have been confused for some time about the black and white birds stranded at Southend which resembled the plumage and cited dimensions of Max Shearwwater Puffinus puffinus (BrĂ¼nnich) more than the Guillemot Uria aalge (Pontoppidan). However, the latest find, at Hut 158 Thorpe Bay on the morning strandline of January 23 2014 showed the bill more clearly than the one in gravel at Shoeburyness on the afternoon strandline of September 30 2013. There was a nasal pore on the rear side of the upper bill rather than a tube nose in the middle of it and the tip of the bill was not curved into a hook. The first find arrived with a N.E. (112°) wind on a strandline trending 215° with the body and webbed feet behind it pointing towards 160°. It was largely ventral-up and facing S.E. into the waves, ab out 0.3 m from the wet limit of the strandline. The neck was however pointed inshore like the bill. When a flexible tape was placed along the resulting sinuosity, it gave an approximate tip of bill to tip of feet length of 16 inches (c. 485 mm). The plumage was entirely black and white, with a pale area around the eyes and a darker one on the tip of the head extending into the neck to some extent. The plumage of the latter find was the same and in that case it had nearly straight stranded dimensions on and along the strandline trending E.W., of 13 inches bill tip to tip of tail, and 16 inches bill tip to tip of grey webbed feet. They pointed west into the wind that day with the intact body again largely ventral-up. In The Seabirds of Britain and Ireland by Cramp et. al. (1974 Country Book Society) Guillemots are said to have an imperfectly known marine distribution in winter when their winter plumage illustration is similar to what I saw except that theirs shows a longer dark grey band under the eyes (pl. 1E). In their 1970 census, it did not return to breed anywhere nearer to Southend than the chalk cliffs of the Isle of Wight and Yorkshire. In summer, it is said to be brown with much less white on the head and evidently these feathers can be entirely molted before the end of September. In Brown et al. (2003, Tracks and Signs etc Helm Press, London), they are reported to molt from late June until the end of October in England.

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