Antoine Sierro

Barbastelle bats (Barbastella spp.) specialize in the predation of moths: implications for foraging tactics and conservation

The diet of barbastelle bats, Barbastella (b.) barbastellus and B. (b.) leucomelas, captured, respectively, in the Swiss Alps and in the Kirghiz Tien Shian and Pamir mountains (central Asia) was investigated through faecal analysis. Location of hunting habitats and data on foraging behaviour of Swiss barbastelle bats were obtained from radiotracking. In either area, ca. 99% of prey by volume consisted of Lepidoptera. The regular occurrence of one small arctiid species in the diet of Swiss barbastelles, as well as the predominance (84%) of tympanate moths among the Lepidoptera sampled at foraging sites suggest that B. barbastellus could prey to a large extent on smaller tympanate moths. Observations of foraging bats showed that, in the study area, barbastelles behaved as typical aerialhawking bat species, although they hunted exclusively just above the forest canopy. This aerial-hawking bat species has seemingly evolved a peculiar foraging technique to overcome the defence system of its probable tympanate prey. The diet of Barbastella appears one of the narrowest among Palaearctic bats. Such a specialization in foraging habits probably points to a higher vulnerability of this species, as compared to other more flexible aerial-hawking bats, to negative changes in the abundance of moth populations. This could explain its current rarity throughout most of Europe.

Habitat use and foraging ecology of the nightjar (Caprimulgus europaeus) in the Swiss Alps: towards a conservation scheme

The European nightjar is one of the most endangered bird species in Switzerland. As its ecology in the country is poorly understood, we collected data on resource exploitation in the upper Rhone valley (Alps). The diet of two adult birds and one nestling consisted primarily of moths (81 and 93% of biomass), which were also the most abundant prey sampled at the study site. Three radiotracked nightjars selectively exploited oak scrubland compared to vineyards and pine forests; vineyard monocultures harbour presumably insufficient moth populations, whereas dense pine stands probably do not provide the flying and foraging requirements of nightjars. The survival of nightjars in Valais probably depends both on the existence of sufficient populations of moths and on the availability of semi-open natural habitats, such as oak scrubland, which seem to offer the best suitable foraging and nesting places.