Who’s for dinner? Bird prey diversity and choice in the great evening bat, Ia io

Abstract

The mysterious predator–prey interaction between bats and nocturnally migrating birds is a very rare and incredible process in natural ecosystems. So far only three avivorous bat species, including two noctule bats ( Nyctalus lasiopterus and Nyctalus aviator ) and the great evening bat ( Ia io ), are known to regularly prey on songbirds during nocturnal avian migration. The information related to the diversity and the characteristics of the birds as prey and the hunting strategy in both species of noctule bats are already clear. However, the diversity of bird prey in the diet of I. io as confirmed by molecular identification remains unknown. Moreover, like hunting insects, it remains unclear whether the avivorous bats opportunistically prey on birds. Here, we used DNA metabarcoding to investigate the bird prey composition, diversity, and choice in diets of I. io . We found I. io consumed 22 species of seven families from Passeriformes with a body mass of 6–19 g, and preferentially selected small‐sized passerine birds for optimizing the benefit/risk trade‐off. Moreover, most of the species preyed upon were migratory birds, while four species were local resident birds, indicating that I. io may adopt both aerial‐hawking and gleaning strategies on songbirds as do the other two noctules. Further, I. io body mass did not influence in prey choice and predation richness on birds, suggesting I. io is an opportunistic avivorous predator. This study provides novel insights into the avian dietary ecology of I. io and completes the analysis of predator/prey interaction between three avivorous bats and nocturnally migrating birds. Our results also indicate bat predation on birds which occurs as an act of ecological opportunity may subject bats to intense natural selection pressure, causing them access to the new diet‐defined adaptive zones.

Seasonal Dietary Shifts Alter the Gut Microbiota of Avivorous Bats: Implication for Adaptation to Energy Harvest and Nutritional Utilization

“…This cave is mainly a colony of I. io males. In the winter, individual bats either hibernate in this cave or migrate farther south to overwinter elsewhere ( 24 ). Our previous studies had shown that individual bats within this population mostly prey on insects in the summer (June to August) and on birds in the autumn (September to November) ( 24 ).…”

“…In the winter, individual bats either hibernate in this cave or migrate farther south to overwinter elsewhere ( 24 ). Our previous studies had shown that individual bats within this population mostly prey on insects in the summer (June to August) and on birds in the autumn (September to November) ( 24 ). Bats were captured using a mist net at the entrance to the cave after they returned from foraging (between 20:00 and 07:00).…”

“…Predation of bats on birds (namely, avivorous bats) is a rare process in the natural world. Of 1,400 bat species ( 21 ), only three temperate-subtropical species, Ia io , Nyctalus lasiopterus , and Nyctalus aviator , are known to prey on insects in summer but also known to hunt nocturnally migrating birds in spring and autumn ( 22 – 24 ). Thus, avivory in bats represents a case of dietary niche expansion from low- to high-quality food resources, since birds have higher nutritional value than invertebrate insects ( 25 ).…”

“…These bats feed on different prey species according to seasonal variation in food resources. They mainly forage on small passerines during bird migrations in spring and autumn, and they mostly feed on insects in summer ( 24 , 26 ). Moreover, our previous study demonstrated by high-throughput sequencing that I. io preys on at least 22 species of passerine birds ( 24 ).…”

“…They mainly forage on small passerines during bird migrations in spring and autumn, and they mostly feed on insects in summer ( 24 , 26 ). Moreover, our previous study demonstrated by high-throughput sequencing that I. io preys on at least 22 species of passerine birds ( 24 ). This dietary shift provides an opportunity for examining the composition and function of gut microbiota during the dietary expansion from an insectivorous diet to a carnivorous (avivorous) diet.…”