Wednesday, 1 August 2007
Exciting tern up for the books!
Yesterday, under Tony's supervision, we cleared the cathedral's nave roof of prey remains and anything else which might block the drainage systems, coming away with a heavy but fortunately only slightly smelly plastic bag full of feathers, heads, wings and feet from a wide range of birds, plus tree leaves and some rather less pleasant gunge!
Some prey remains were easy to identify: a woodcock's wings and head, skulls of golden plover, lapwing and starling, wings of several moorhens, pigeons etc, all interesting but all species we've found before.
However two items stood out immediately: the dried up remains of a tern with head and wings intact and the head and feet of a whimbrel. Closer investigation of the tern showed that one of its tiny legs was still present and it bore a ring - a most exciting discovery!
Even more exciting was the inscription on the ring: which read; 4392757 Riksmuseum Stockholm....so this bird was ringed in Sweden and had been caught by a peregrine on its spring migration through Derbyshire. We have sent the details off to Stockholm and hope to discover soon exactly when and where it was ringed....
The tarsus of the leg, as you can see from the photo, was very short (14 or 15mm) which identifies the bird as an arctic tern. Its very closely related cousin, the common tern, has a longer tarsus (19-21mm) and there is no overlap, which makes identification easier.
Checking the records, we noted that there was a large passage of arctic terns through the south of the county (within 10-15 kms. of Derby) at the end of April and beginning of May with the largest flock being of 80 birds. So it is likely, although not definite of course, that this bird was caught at that time.
The whimbrel whose skull we found probably passed over Derbyshire about the same time. This wader breeds far to the north, with very small numbers moving up through the Midlands.The photo shows the woodcock and whimbrel heads, accompanied by drawings of each. The drawings show just the bones which underlie the horny sheaths which are still present in the specimens which therefore look a bit larger.
Both the arctic tern and the whimbrel are new species for the list of prey identified at Derby since we began recording in 2005.
The jack snipe was only the third one we have found. This rare bird may well have been caught flying over Derby sometime during the winter or possibly, like the tern and whimbrel, on its migration north in spring. None of these species breeds locally.
There are still some feathers and feet requiring close scrutiny and we may end up sending them down to Ed Drewitt at Bristol Museum.....so watch this space.
Incidentally, Ed has been studying the prey of urban peregrines in the UK for a number of years and can identify even the smallest feather from the drabbest of birds. So this is a good moment to thank him for all his expert help and support over the last two years. His alltime UK prey list now numbers over 100 species whereas our Derby list is just over 40, so we've a way to go yet!
Ed tells me there have been a few other foreign-ringed birds found at other peregrine sites, eg black headed gulls from Lithuania and Poland, but no arctic terns!