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

Abstract

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.

Great tits search for, capture, kill and eat hibernating bats

“…A recently discovered case is the predation of a large aerial hawking bat on night migrating songbirds (Popa-Lisseanu et al 2007). Conversely, here we present evidence for opportunistic predation of a songbird, the great tit (Parus major), on bats.…”

Origins and migratory patterns of bats killed by wind turbines in southern Alberta: evidence from stable isotopes

“…Stable-isotope analysis of bat tissue has been used in numerous dietary studies (Fleming et al 1993, Voigt and Kelm 2006, Popa-Lisseanu et al 2007, Painter et al 2009, Cryan et al 2012, and also to investigate the origins and migratory movements of bats. (Cryan et al 2004, Cryan et al 2014.…”

Nyctalus lasiopterus Schreber, 1780 (Chiroptera: Vespertilionidae): first record for Kornati archipelago and first recent capture for Croatia

“…This can be further linked with the suggestion that distribution of greater noctule closely follows the migration paths and high abundance of passerine birds. As a nocturnal ''ecological equivalent'' of N. lasiopterus, Eleonora's Falcon, Falco eleonorae, catches prey in the air during the autumn migration from Europe to Africa, and switches its diet from mostly large insects to catching migrating birds (Ristow et al 1986, Popa-Lisseanu et al 2007. A few sightings of F. eleonorae were recorded in the Kornati archipelago (Lukač et al 1997), and nests were confirmed on cliffs for islands distant from the coastline (Figure 1, Š ćetarić 2001, Š ćetarić-Legan andPiasevoli 2005, G. Piasevoli personal communication).…”