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!

10 comments:

helenhoward said...

how fascinating but sad in a way that the poor birds had come so far but to end up as dinner for the pereguins. i have learnt a great deal from the diaries ie i had never heard of a hobbie or indeed of a whimbrel till reading these pages and as already stated really interesting and very grateful that you can share your knowledge with us.

Anonymous said...

lerning a great deal from these diary entries never heard of a whimbrel, it is sad when you see the remains as all birds are beautiful in their own right, but such is life and for them to fly so far as well and turn into a dinner after such a long hard journey, thanks very much for sharing your knowledge it makes fascinating reading, i keep looking at the webcams for the peregrines.

Nick Brown said...

Peregrines have such a wide food spectrum they do not make any serious impact on the population of any one species.
And of course they and their prey have lived alongside each other for thousands of years, more or less in balance.
And the theory is that by picking off the weaker individuals, predators actually help their prey to stay 'fit' in the biological sense of the word.
So, if I were a whimbrel or tern, I'd guess I'd rather become prey for a peregrine than be shot by humans or have my nesting or wintering grounds ruined by peat extraction so that someone can grow flowers in their garden, or have them exploited for oil so they can drive to the garden centre to collect said peat.
Here endeth the first (ecology) lesson...sorry if it sounded pompous!
Nick B
Ps Whimbrel breed on peaty bogs and moors, hence my reference to peat extraction. While I never by peat I do have a car so I'm also part of the problem for sure.....

Sue H, Bucks said...

I've forgotten where you live HelenHoward - are you Rhode Island? Wherever, I'm pretty sure it's the U.S. and as such I'm very impressed at your knowledge of British birds - much greater than my knowledge of american ones! The analysis of prey items is so interesting. A bit (OK, a lot then) sad for the individuals that ended up on the menu but our birds would be dead without them. At least they must have had enough to eat and we didn't end up with the kind of grisley business that occurred on the "Springwatch" TV programme with the Eden Project Barn Owls. How exciting to have actually found a ring - glad our birds weren't daft enough to try to eat that too! I keep looking at the bird pictures in the previous entry. They are all lovely but I am quite taken with the Greg Poole one. Is that one that's in the Derby Museum, by any chance?
Sue H, Bucks

helenhoward said...

hi sue from bucks
I wish i did live in Rhode Island I am actually a derbyshire lass but there is no harm in hoping I live in such exotic quarters!!

Karen Anne in RI :-) said...

How's the flooding situation over there now? Is the danger of more flooding past?

Nick Brown said...

Greg Poole's work isn't at Derby but can be seen at www.gregpoole.co.uk and to see the work of other excellent wildlife artists including Greg and Peter try The Society of Wildlife Artists annual exhibition in London in September (details at www.swla.co.uk where also go to the members list to see examples of each artists work).
NB

helenhoward said...

hi karen anne
the flooding seems to be over for now but no doubt it will return and no doubt we will still have water shortages!!

Anonymous said...

Can you post a picture of our pigeon rings so we can be 100% sure your peregrines did kill them thanks.
Steve

Anonymous said...

Or even better could you give us the ring numbers so we can cross them of thanks.
Steve