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, 2 (2), e205

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


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

Ana G Popa-Lisseanu et al. PLoS One.


Along food chains, i.e., at different trophic levels, the most abundant taxa often represent exceptional food reservoirs, and are hence the main target of consumers and predators. The capacity of an individual consumer to opportunistically switch towards an abundant food source, for instance, a prey that suddenly becomes available in its environment, may offer such strong selective advantages that ecological innovations may appear and spread rapidly. New predator-prey relationships are likely to evolve even faster when a diet switch involves the exploitation of an unsaturated resource for which few or no other species compete. Using stable isotopes of carbon and nitrogen as dietary tracers, we provide here strong support to the controversial hypothesis that the giant noctule bat Nyctalus lasiopterus feeds on the wing upon the multitude of flying passerines during their nocturnal migratory journeys, a resource which, while showing a predictable distribution in space and time, is only seasonally available. So far, no predator had been reported to exploit this extraordinarily diverse and abundant food reservoir represented by nocturnally migrating passerines.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.


Figure 1
Figure 1. Nyctalus lasiopterus showing its impressive teeth to the researchers.
Figure 2
Figure 2. Stable isotope values (δ13C and δ15N) found in bat blood in 2003 (a) and 2004 (b).
Individual samples are depicted by small, empty symbols in color, whilst large black symbols show corresponding average group values (seasons are shown with different colours; labelling on both graphs). Mean (±SE) values for potential prey are also shown as small diamonds with bi-directional error bars (labels in 2a). Boxes represent the range of expected values, considering 99% CI for prey and accounting for fractionation factors in the blood of bats that would mirror a pure invertebrate diet (full frames) or a pure bird diet (dashed frames) in spring (grey frames), summer and autumn (black frames, labels in 2b), respectively (see Methods). Partial labelling for prey isotopic signatures («crosses») and expected dietary isotopic signatures (rectangular frames) are shown to enhance clarity.
Figure 3
Figure 3. Seasonal variation in isotopic composition of blood of Nyctalus lasiopterus.
Means±SE for δ13C (purple circles) and δ15N (orange squares) for each sampling event are given. Numbers at the top of the figure designate sample size. The black line indicates nocturnal migration density of small passerines tracked by radar in southern Spain . The shaded area represents proportion of feathers found in faecal pellets of Nyctalus lasiopterus .

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