Mixed bird flocks: patterns of activity and species composition in a region of the Central Andes of Colombia

Abstract

Mixed bird flocks are groups of individuals from different species that travel and forage together. Such
groups are common in several bird communities around the world. We present species composition and activity patterns
of mixed bird flocks in a region of the Central Andes of Colombia. We compared the number of species per flock, as
well as the number of flocks among 3 different habitats. We tested hypotheses concerning the flocks daily activity and
the co-occurrences of species within them. We recorded 75 species, and the species number per flock varied from 4 to
21. Our data suggest that habitat affects the number of flocks but not their species number, and that the activity of flocks
is similar throughout the day. In addition, the association of birds in flocks is affected by interspecific facilitation, with
some species co-occurrences found more times than expected by chance. We hypothesize that some tanager species
could have a role in flock cohesion. We witnessed 2 predator attacks upon flocks, a number of agonistic interactions
among flock members, and squirrels following bird flocks. Our results meet some general patterns described for mixed
bird flocks.