B.T.O. Atlas of Migration.

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Suffolk Natural History, Vol. 35

THE BTO MIGRATION ATLAS CHRIS WERNHAM After the Swallow, the Arctic Tern is probably one of the best-known avian migrants, famous for its annual journcy of up to 9000 miles each way between its breeding grounds in the northern hemisphere and wintering areas as far south as the Antarctic. Similarly, another of our breeding seabirds, the Manx Shearwater, also travels a long way (about 6000 miles each way) to rieh fishing areas off the east coast of South America during the winter. In addition to that, female shearwaters travel up to 500 miles from their breeding colonies to the Bay of Biscay to feast on sardines during the period of egg formation in spring. We have decidcd to use this amazing seabird migrant as the flagship species for our new project, the BTO Migration Atlas. The BTO and the Ringing Scheme The British Trust for Ornithology has had a long history of studies on bird migration because it is the Organisation responsible for the co-ordination of the British and Irish Ringing Scheme, which has been running since 1909. I am sure that most of you already know about bird ringing but, for those that do not, I will give you a brief introduetion. Ringing involves putting a small metal ring with a unique number and return address onto a bird's leg. Rings are made in a variety of shapes and sizes so that there is a type suitable for almost every species. This activity is carried out by around 2000 highly-trained, licensed ringers all over Britain and Ireland, mostly as a hobby in their spare time. Ringers are only permitted to ring after extensive training, and the welfare of the birds is paramount. When a ringed bird is found dead, or re-caught by a ringer, or seen by an observer because it has colour rings, and reported to the BTO, this is termed a 'recovery'. The unique number on the ring allows the individual bird to be traced. The original motivation for ringing birds was to find out where they went. But now, with new analytical techniques and the power of Computers we can also use ringing information to investigate survival rates, changes in bird numbers and produetivity. Rationale behind the Migration Atlas Fifty years ago only 820,000 birds had been ringed in Britain and Ireland, less than the current annual total in some years, and foreign recoveries were rare and exciting. The map of 'outstanding recovcries' from the 1948 BTO Annual Report showed exciting long distance movements, such as that of a Sandwich Tern to Angola and a Kittiwakc across the Atlantic. A Wheatear recovered in Portugal was the first recovery of any species from the newly-established Fair Isle Bird Observatory. Now, 50 years on, we have much more information available to us: over 25 million birds have been ringed since 1909, resulting in over Vi million recoveries of 260 species. Now the BTO reeeives well over 10,000 recoveries every year. This is why it is now time to collate the information on bird movements from ring recoveries into a Single volume, to 'take stock' and to decide what information we should aim to collect via ringing in the future.

Trans. Suffolk Nat. Soc. 35

(1999)


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