British Ornithologists' Union Centenary Expedition

Expedition to Ascension Island

This special postage stamp issue marks the 50th anniversary of the expedition mounted in 1957-1959 to celebrate the centenary of the British Ornithologists' Union (BOU), one of the oldest ornithological societies in the world. This postage stamp issue of Ascension Island exists of eight postage stamps.
As a part of the celebration the British Ornithologists' Union decided to send an expedition to Ascension Island, undertaking pioneering studies of the biology of tropical seabirds. At that time, ornithologists were actively investigating the way in which bird breeding cycles were controlled, both by internal physiological mechanisms and by the characteristics of their environment. There was a report that on Ascension, the Wideawakes (aka Sooty Terns) were returning to breed en masse every 9.6 months, so that breeding occurred earlier each year. Since all birds need adequate food supplies when breeding, did this imply that the marine environment on which the terns depended was effectively seasonless? If so, how were the other seabird species on the island behaving?

Miracle Mile

To try to answer these and related questions, the British Ornithologists' Union expedition spent 18 months on Ascension, from September 1957 until April 1959. The party had to be relatively self-sufficient. Huts for the base camp near Mars Bay (see 15p stamp), a well used Land Rover kindly donated by the makers, and a ship's lifeboat (named Ibis after the logo of the BOU) were brought from England on a Union Castle liner. Most of the food and equipment for 18 months also came from England, although fresh produce was sometimes available from the mountain farm. Freshwater was collected regularly from the Pan Am based that had just been established at Miracle Mile.

Boatswainbird Island

The Wideawakes nested close to camp (see 25p stamp), but most of the seabirds could only be studied on Boatswainbird Island. With the help of Cable & Wireless staff a mooring for Ibis was put down in Northeast Bay. Every few weeks, stores were ferried to Ibis using the expedition's dinghy Overdraft (see 50p stamp) and taken round to Boatswainbird Island, where a small but was constructed on the landing platform (see 40p stamp). Ibis could not be moored there overnight, so two people at a time were marooned on the island, usually for about five days. There was no radio communication and the date of relief was never certain because rollers sometimes made it impossible to use the dinghy at Northeast Bay.

Breeding cycles

Data obtained by the expedition demonstrated a variety of breeding cycles among the seabirds. Tropic birds bred on less-than-annual cycles, members of each pair returning to breed again as soon as they had finished the moult that followed the previous breeding attempt. Successful rearing of a chick took longer than a failed attempt, so cycles were longer in successful than in failed breeders, with the result that birds could be found breeding at any time of year. Individual ringed Wideawakes showed a similar pattern, but the intense sociality of this species maintained the synchronized breeding in the population as a whole. The White Tern showed diffuse peaks in breeding at annual intervals, while the Madeiran Storm Petrel showed more strictly annual breeding. Other species showed a variety of less distinct patterns.

Fossils

Expedition members also studied sub fossils of birds that had been present on the main island in the past. Most intriguing was the discovery - in bottle-shaped volcanic pits locally referred to as fumaroles - of bones of a flightless rail which was seen by the traveler Peter Mundy in 1656 (see postage stamp) but which quickly became extinct. Other bones found there and in phosphate deposits on lava flows showed that many kinds of seabirds had nested on the main island before the introduction of rats and feral cats. The recent eradication of the cats - first suggested during the course of the British Ornithologists' Union expedition - is now allowing recolonization of the island by some seabirds that survived in small numbers on Boatswainbird Island.

Technical Details of the postage stamps

Issue: Ascension Island, 10th December 2007
Designer: Nick Shewring
Photography: All images courtesy of Philip Ashmole
Print: Lithography by BDT International Security Printing
Perforation: 14 per 2cms
Stamp size: 28.45 x 42.58mm
Values: 2 x 15p, 2 x 25p, 2 x 40p, 2 x 50p

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