Giant noctule bats eat nocturnally migrating birds

From Science Blog:

It was until now believed that nocturnally migrating songbirds, while venturing into the unfamiliar night sky for accomplishing their long, challenging trans-continental migrations, could at least release anti-predator vigilance thanks to the concealment of darkness.

A new study by Spanish and Swiss scientists – published this week in PLoS ONE – shows that migration at night is not without predation risk for passerines.

A unique creature is indeed capable of exploiting the formidable food source represented by the billions of high-flying, Eurasian songbirds which engage twice a year into long-distance, north-south or south-north nocturnal movements.

The danger seems especially acute where birds’ flight routes converge around the Mediterranean basin, such as the Iberian Peninsula.

This newly recognized hazard adds to the numerous obstacles that sea and desert crossings already represent for fragile migratory passerines.

Actually, the newly uncovered danger comes from the deep black sky, in the form of a 45 cm wing-spanned aerial-hawking mammal, equipped with sharp canines and an efficient radar system which remains probably largely inaudible to songbirds.

In 2001, Carlos Ibáñez and his colleagues at the Doñana Biological Station in Seville, Spain, suggested that the giant noctule bat (Nyctalus lasiopterus), a rare European species occurring principally in the Mediterranean, may feed to a large extent on birds (Proceedings of the National Academy of Sciences 98, 9700-9702).

They had found numerous feathers in the faeces of Spanish giant noctules, with occurrence peaks in the diet in spring and autumn, i.e. during main songbirds’ seasonal migration.

This contrasted strikingly with food composition of other European bat species which all feed exclusively on invertebrates!

Research in Italy led to similar conclusions:

An analysis of 59 droppings of the greater noctule Nyctalus lasiopterus, collected either during direct handling of the bat or from the bat-boxes used as shelters in the Pian di Novello Natural Reserve (Tuscany, Italy), has shown that it is a partial carnivore.

The content of the samples, collected in October and November of 1995 and in September and October of 1996 and 1997, consisted mainly of bird feathers identified as those of the robin Erithacus rubecula and the blue tit Parus caeruleus.

The presence of feathers during the 3 consecutive years of the study period confirms that the diet of the greater noctule in this area is not based exclusively on arthropods as was previously suggested.

Spanish researchers have confirmed that the largest bat in Europe, Nyctalus lasiopterus, was present in north-eastern Spain during the Late Pleistocene (between 120,000 and 10,000 years ago). The Greater Noctule fossils found in the excavation site at Abríc Romaní (Barcelona) prove that this bat had a greater geographical presence more than 10,000 years ago than it does today, having declined due to the reduction in vegetation cover: here.

The bumblebee bat, world’s smallest bat, is said to have diverged evolutionally from other bats 43 million years ago; Leidsch Dagblad 18 January 2007.

Nyctalus leisleri bats in the Netherlands: here.

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