Picky fruit-eating birds are more flexible

The Plumbeous pigeon is a picky eater. Whereas its relatives on European streets and squares feed on whatever they encounter, its South American relative almost exclusively feeds on certain fruits. Together with other birds such as toucans or the turkey-like guans it belongs to a bunch of large fruit-eating birds that are specialized on particular types of fruits. One might think that being peculiar goes hand-in-hand with being inflexible in food choice -- however, it does not.

"We compared neotropic fruit-eating birds that are specialized on a small range of fruit resources in a particular season with birds that eat a large ranage of fruits. The specialists are those which are most flexible in adapting their foraging choices across seasons," explains Irene Bender, Senckenberg Biodiversity and Climate Research Centre and German Centre for Integrative Biodiversity Research (iDiv), lead author of a new study on this topic. She adds "The flexible avian fruit eaters prefer to feed on large fruits. However, their favourite resources are not constantly available throughout the year which forces them to switch."

The researchers' surprising observations shed light on the question how species might respond to resource fluctuations that are not naturally determined. "This flexibility of consumer species may be an important, but so far widely neglected mechanism that could stabilize consumer-resource relationships, for instance in response to human disturbance and environmental change. Being flexible might mean that specialized foragers are able to adapt to future changes in resource availability." says Dr. Matthias Schleuning, Senckenberg Biodiversity and Climate Research Centre.

The study was based on observational records by a team around Irene Bender and Matthias Dehling of the fruit choices of birds in the Manú Biosphere Reserve on the western slopes of the Andes in Peru. The team also measured traits of the plants which provided the fruits, such as plant height and fruit size. The flexibility of bird species was defined as their ability to switch seasonally among plant species with different traits; their specialization was measured by comparing their fruit choices to those of other bird species in the community.