Bat predation on nocturnally migrating birds

Abstract

Bat predation on birds is a very rare phenomenon in nature. Most documented reports of bird-eating bats refer to tropical bats that occasionally capture resting birds. Millions of small birds concentrate and cross over the world's temperate regions during migration, mainly at night, but no nocturnal predators are known to benefit from this enormous food resource. An analysis of 14,000 fecal pellets of the greater noctule bat (Nyctalus lasiopterus) reveals that this species captures and eats large numbers of migrating passerines, making it the only bat species so far known that regularly preys on birds. The echolocation characteristics and wing morphology of this species strongly suggest that it captures birds in flight.A ctivity patterns in birds and bats differ considerably, and ecological and behavioral interactions between the two groups are rare (1). Millions of Palaearctic birds fly seasonally across the Mediterranean, mainly at night, north and south between summer and winter quarters (2). During their migrating journeys, birds concentrate and stop over in large numbers in the Mediterranean region. Only two diurnal birds of prey (Falco eleonorae and Falco concolor) show specific adaptations to feed on migrating birds in this area (3,4). Surprisingly, no nocturnal predators are known to prey on migrating birds. At least a few bat species would be expected to exploit this food resource, as the order exhibits a remarkably wide range of lifestyles and foraging strategies, as well as a high diversity of echolocation calls (5) and flight behaviors. However, predation on birds has been reported from only three or four of the dozen known carnivorous bat species (6, 7), these being mainly large tropical bats that occasionally capture resting birds by using a gleaning foraging strategy. Bats have never been known to chase birds in flight. The first report of bird predation by a bat in temperate regions was of the greater noctule (Nyctalus lasiopterus) (8), one of the rarest and least known mammals in Europe. We here report the regular occurrence of bird predation by this species, based on the analysis of fecal pellets. The echolocation capabilities and wing morphology of the greater noctule adapt it to chase and capture of birds in flight. Materials and MethodsWe examined over 14,000 fecal pellets of N. lasiopterus collected in two ways. First, fecal pellets were collected between August 1998 and October 2000 from 170 individual N. lasiopterus netted over water courses mainly in a mountainous area of La Rioja (northern Spain; 100 bats) and as they returned to their treeroosts in a city-park in Seville (Andalusia, southern Spain; 70 bats). The bats were individually kept in cloth bags until the next evening and thereafter sexed, weighed, measured, and released at the site of capture. Only ten bats yielded no feces and a total of 2,347 pellets was collected. Second, samples of fecal pellets were collected every 10 days from May to October 1999 under a maternity colony of around 80 N. lasiopterus that roost under three...

Bats' Conquest of a Formidable Foraging Niche: The Myriads of Nocturnally Migrating Songbirds

“…The unexpected finding of bird feathers in the faecal pellets of Nyctalus lasiopterus [16], [17] (Figure 1), a rare Mediterranean aerial-hawking bat, caused substantial controversy. The conclusion drawn by the authors that giant noctules feed on migrating birds [17] was severely criticized by some scientists who suggested a mistaken or selective ingestion of hovering feathers but not birds [18].…”

“…The conclusion drawn by the authors that giant noctules feed on migrating birds [17] was severely criticized by some scientists who suggested a mistaken or selective ingestion of hovering feathers but not birds [18]. The reason for this scepticism was probably the discovery of a previously undocumented foraging strategy and predator-prey relationship: indeed, no predators were known to hunt in the open upon nocturnally migrating birds, despite the immense resource that the latter potentially represent.…”

New evidence for the greater noctule bat (Nyctalus lasiopterus) in the Late Pleistocene of western Europe

“…Its habitat is linked to deciduous forests, using cavities in trees as daytime shelters. It is the only species in Europe known to prey on small birds [10,12]. In tum, it is occasionally a prey for Tyto alba and Bubo bubo.…”

Transposable elements and small RNAs: Genomic fuel for species diversity

“…the species may be primarily insectivorous, and only occasionally piscivorous). A better option may be species that prey on migratory birds, such as Nyctalus lasiopterus, 43 Nyctalus aviator, 44 or Ia io, 45 where up to 70% of individuals prey on birds during peak migration seasons. 43 Even more dramatically, as a facultative nectarivore Antrozous pallidus is the only known Vespertilionid to include plant material in the diet.…”

“…A better option may be species that prey on migratory birds, such as Nyctalus lasiopterus, 43 Nyctalus aviator, 44 or Ia io, 45 where up to 70% of individuals prey on birds during peak migration seasons. 43 Even more dramatically, as a facultative nectarivore Antrozous pallidus is the only known Vespertilionid to include plant material in the diet. 46 Compared to insectivorous diets, the inclusion of vertebrate prey (fish or birds) or nectar may present altered gene expression patterns.…”