The relationships of breeding stage to daytime singing behaviour and
song perch height in Bermuda White-eyed Vireos (Vireo griseus
bermudianus)
Abstract
Bird song is crucial for attracting mates and defending territories, but
different types of song or different singing behaviours may be involved
in acquiring or maintaining each resource. Furthermore, male songbirds
may adjust when and where they sing throughout the breeding season,
depending on their breeding stage. However, such relationships remain
untested in several avian taxa. Here, we studied male Bermuda White-eyed
Vireos (Vireo griseus bermudianus), a passerine with two distinct song
types (discrete and rambling), to test the mate attraction, territory
defence, and nesting stage hypotheses. We compare song rate and song
perch height among different stages of the breeding season and during
the non-breeding season. We show that male vireos produce both song
types during the breeding and non-breeding seasons, suggesting dual
roles in mate choice and territorial defence. Singing rate did not
differ between the two seasons, but, within the breeding season, males
without nesting duties had significantly higher song rates than males
with nesting duties. Song rate was lowest during the nestling stage,
which coincided with the highest rate of nest predation. Song perch
height was higher during the breeding season versus non-breeding season,
among males without nesting duties compared to males with nesting
duties, and when males produced discrete versus rambling songs. Our
findings suggest that male vireos increase their conspicuousness to
prospecting females by increasing singing rate and song perch height,
and that they sing during the breeding and non-breeding seasons to
defend year-round territories. Collectively, our study supports the mate
attraction and territory defence hypotheses of bird song and suggests
that Bermuda White-eyed Vireos adjust their singing rate in response to
nest predation risk.