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 (Brünnich) 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.

Frogs stranded from sea

Frogs and other amphibians are absent from islands and prior to introductions by Man had a lower diversity in England than mainland Europe. Two dead frogs found stranded at Southend-on-Sea recently (Sept. 21 2013, Hut 249 Thorpe Bay; November 18 2013 Lynton Road Bastion 855 m to West) had respective stranded lengths of c.160 and c.130 mm consistent with them being adult Common Frogs Rana temporaria L. But it is possible that they were small individuals of the Marsh Frog R. ridibunda introduced into Kent marshes in 1935. Their dorsal skin was uniformly dark grey and both it and the grey and white mottled ventral skin displayed thickenings into sub-mm diameter spots seen on Marsh Frogs. It is also unclear if they had been flushed out of the habitat of those frogs, or the more general terrestrial and pond environments. The diagram shows the geometry of the bones and orientation in seawater of the clearly dried frog when refloated after another day in rising tides and about nine hours in a plastic bag on November 19th. When seen on the 18th, it had a ventral-up orientation parallel to the seaward side of the sandy berm of the latest morning tide, with the legs pointing west (or more exactly towards 280°, 110 mm South of the sand wet limit trending 269°). On the 19th it had much the same position except it was now dorsal-up and the strandline itself had moved 2.5 m up the beach. The skin was entirely intact but darker than on living frogs (presumably green) and thrown into longitudinal folds plus a few transverse doral ones behind the head. The length of the body (excluding limbs) was 60 mm. After being placed in a tank of seawater at 9°C (decreasing to 8°C overnight), the corpse developed a posterior-down orientation with the waterline level with the eyes. In this initial desiccated state the hind limbs were flexed and twisted so that they touched each other where the tibio-fibula joins the split astragalus and calcaneum bones. My measurements made via the glass tank wall in mm of the depth and horizontal distance after 3 and 13 hours are illustrated on graph paper with a cm grid. The 3 hour stage is on the left and the ventral side is facing the glass. The hind limbs returned to the more straight position seen on the beach and at least in the region around the femur had swollen into a more natural diameter. The hind limbs were found to have been more flexible than they ever were on the beach when the frog was finally taken out of the water after 16 hours (having then just sunk in the orientation seen on the 13 hour drawing). By contrast, the forelimbs remained in a relatively bent and stiff posture not fully explained by the ventral view. In an anterior view, the left humerus extended ventrally to a position 20 mm from the dorsal surface of the head, while the right humerus was raised above that level with the radio-ulna flexed back down parallel to it. On the left side, the radio-ulna was parallel to the median plane of the body and formed a right-angled joint with the carpus lying parallel to the body about 18 mm from it. On the right side, this region of the forelimb was directly pressed against the ventral surface with the metacarpals curving away from it. When vertical in the water they also curved downwards. Originally the water line had formed a chord that included the eyes, but after three hours this had been reduced to a dry elevation around 3.5 mm around the nose. A gas bubble was observed in the eye socket and suggested that air was slowly lost that way, while water entered via the skin rather than the closed mouth. After 13 hours, the displacement volume had clearly been enlarged by swelling of the torso and hind limbs, while dry emergent cords on the nose had a reduced elevation of around 1 mm. Therefore, although decomposition gases may well have been generated to permit the frog to strand and during refloation, the overall density must have increased by addition of water inside the skin until it sank at 1.026 g/m density. Initial drowning would involve water entering the lungs but there might also be osmotic processes operating via the skin that the kidneys of the non-marine and largely terrestrial adaptations of adult frog could not cope with. One would imagine that water would move out, or more likely salt would move into the living frog, and in this dead intact state any initial drying was clearly reversed, but evidently not far in seawater. The September 2012 find represented a more likely swimming orientation with both the forelimbs bent around the head and the hind limbs extending parallel to each other down the sand (pointing towards 224°, situated 180 mm from the wet sand limit trending 304°). It now seems likely that this corpse, which had a more realistically swollen region around the backbone, had arrived with the hind limbs hanging below a vertical axis like a dragging anchor.

Dead frog in seawater for 3 (left) and 13 hours