Bird Island’s connection with the arctic

Curlew Sandpipers on the hotel lawn, July 2015
Curlew Sandpipers on the hotel lawn, July 2015

Yes, even at almost 4 degrees south of the equator, Bird Island is affected by events in the arctic. In the northern autumn a variety of birds that breed in the arctic tundra arrive on the island and make it their home until the following spring. These are shorebirds and include especially Ruddy Turnstones, Whimbrels, Grey Plovers and Curlew Sandpipers, but a wide variety of other species occur less commonly.

Whimbrels, Grey Plovers and Turnstones on the beach, June 2010
Whimbrels, Grey Plovers and Turnstones on the beach, June 2010

These birds normally arrive in September-October and depart in March-April but some decide to spend what should be their breeding season on the island as well. These individuals are assumed to be young birds that are not yet old enough to breed and many of them do not moult into their more gaudy breeding plumages. The number of birds that spend the northern summer on Bird Island varies from year to year, but small numbers of Curlew Sandpipers, Whimbrels and Grey Plovers are usually to be found on the lawns around the hotel and the short grass on the airstrip. Fifty or more Ruddy Turnstones often spend the northern summer on the island, feeding on the beaches as well as the mown grass areas; and they even occasionally visit the tables in the hotel restaurant! On the beaches a few Sanderlings can usually be seen and occasionally we have seen Little Stint, Wood Sandpiper, Terek Sandpiper and Asiatic Golden Plover during the Sooty Tern season from May to September, having decided to forego a northward migration.

A Turnstone investigates restaurant food
A Turnstone investigates restaurant food

2016 is proving exceptional, however, and is remarkable for the paucity of shorebirds. We have seen no Curlew Sandpipers or Grey Plovers, and Ruddy Turnstones are much less common than usual, with only four individuals seen. Whimbrels are also less numerous than usual and their loud rippling calls are notably absent from the grassy areas around the Sooty Tern colony.

The absence or scarcity of these birds this year suggests that they produced fewer young than usual during the 2015 breeding season. Breeding failures have been reported before and are sometimes attributed to collapses in the cyclical Lemming populations of the high arctic. When Lemming numbers are high, they support high populations of their predators, such as Snowy Owls and Arctic Foxes, but when Lemming numbers fall these predators have to search for alternative prey. At such times they can wreak havoc on breeding shorebirds. Reduced numbers of shorebirds on their wintering grounds could also be caused by catastrophic events on their migration routes, or by changes on the wintering grounds themselves. The habitats used by shorebirds on Bird Island appear no different from earlier seasons and I am unaware of events that might have caused high mortality along migration routes over Asia or over the northern Indian Ocean. Two species of shorebirds that breed in southern Asia, Greater Sand Plover and Lesser Sand Plover, are here in their usual numbers this June.

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