Barn swallows (Hirundo rustica) are widespread, but their numbers are seriously declining with the industrialization of agriculture and abandonment of barns and stables. It was therefore an important finding when a team of Earthwatch volunteers discovered an enormous night roost of barn swallows in Mwea National Reserve, Kenya, last December.

The night roost was found by volunteers on Earthwatch's Europe-Africa Songbird Migration project, led by principal investigators Dr. Gabor Lövei (Danish Institute of Agricultural Sciences) and Colin Jackson (National Museums of Kenya). A first estimate of the total number of barn swallows at the site, in a Sesbania thicket on the shore of the Kamburu Reservoir, is over 1 million birds.

"This find is very significant," said Lövei. "According to estimates, there are about 80 million barn swallows in the world. Any site that harbors more than 1 percent of the estimated world population is classified as an 'Important Bird Area' and such a site is considered of outstanding importance for that species."

Barn swallows breed in loose colonies across the northern hemisphere, migrating to South America and Africa in the winter. They are known to gather in huge numbers at suitable night roosts during migration and wintering. The birds in the Mwea roost may have migrated from eastern Europe, European Russia, or central Asia. During the day these birds dispersed to an estimated 35-kilometer radius from the roost, where they fattened up on flying insects for the migration north for the breeding season.

Lovei's teams in southern Italy have also observed a swallow roost, but on a much smaller scale, with no more than 15,000 birds in a night. Huge roosts are known to exist in West Africa, in the reedbeds of large rivers, but this is the first roost of its size found in East Africa.

The Earthwatch team that discovered the roost made an initial exploration of the site, and banded about 300 birds over two evenings. Teams on Europe-Africa Songbird Migration this season will return to do more banding at the site and make more precise estimates of bird numbers. Lövei is collaborating with an international swallow project, and plans to collect feathers for stable isotope identification, which will give some indication of the birds' origin.

Mwea National Reserve, about 140 kilometers from Nairobi, Kenya, is already classified as an 'Important Birding Area' (IBA) because of the presence of a threatened endemic bird species, Hinde's babbler (Turdoides hindei). The discovery of the barn swallow night roost is further support for the careful conservation of this valuable natural area.

"Discovering a new IBA for a species does not happen every year," said Lövei. "I am sure that there are more IBAs to discover in the tropical countries, but this does not diminish the importance of our discovery."

For information on volunteering on the Europe-Africa Songbird Migration project, click here.

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