Wednesday, 13 June 2007

Rare breeding birds gain a foothold in Britain

North American birds are becoming increasingly happy to settle in Britain and breed, according to the latest report from the Rare Breeding Birds Panel (RBBP).

Three Nearctic species may just be on the verge of becoming regular breeders, according to the RBBP’s detailed assessment of recent data from around the country: Green-winged Teal, Ring-necked Duck and Pectoral Sandpiper have all bred or attempted to do so.

A male Green-winged Teal, considered to be a wild bird, paired with a female Common Teal in Lancashire and North Merseyside, maintaining their pair bond for at least three weeks in June 2004, though no young were seen.

The story was slightly different with Ring-necked Duck: previously reported as paired with Common Pochards in both 1977 and 1998 (again with no young produced), a single male was present in Lincolnshire for nine days during May 2003. However, in 2004 a male paired with a female Tufted Duck on the Outer Hebrides and the eventual result was two hatched young, though whether they fledged or not is unknown. Given the number of each seen annually in Britain nowadays it may only be a matter of time before a pure pair meet and produce young.

The story with Pectoral Sandpiper is even more impressive. Following a bird present in mid-July and August 2003, there were at least two separate breeding attempts in 2004 by different pairs at widely separated locations, thought to possibly be the first such attempts in the Western Palearctic (note that this species breeds to the east of Britain, in north-east Siberia, as well as across the Atlantic).

One of the occupied sites was the same as the 2003 site and display was noted there, eventually resulting in sightings of an adult accompanied by a fresh juvenile in July, with both remaining until October.

Secretary of the RBBP, Mark Holling, commented in the report that it seems “very likely” that breeding did in fact occur (mainland Scotland) and that the activities of the other pair (Outer Hebrides) represent the first breeding attempt in the Western Palearctic.

Mr Holling also explained: “Obviously it is far too early too consider the occurrences mentioned in our report as possibly the start of colonisation. However, it will be interesting to see whether future large scale arrivals are followed by further breeding attempts”.

Furthermore, the report reveals that it wasn’t just Nearctic species attempting to gain a foothold in Britain, and that a pair of Smew, a duck which breeds from Scandinavia eastwards through Russia, were seen copulating on an inland Scottish loch.

In the future it seems likely that climate change may be the catalyst for certain species to colonise Britain, though not North American species. The dynamic at work with these species is well understood and can be attributed to the increasing numbers of certain accidentals reaching our shores.

Reference: Holling, H, et al. 2007. Rare breeding birds in the United Kingdom in 2003 and 2004. British Birds 100: 321-366.