July/August Cover

Submitted by Michi on 31 July 2023.

The July/August cover features a Bermuda white-eyed vireo Vireo griseus bermudianus photgraphed by Miguel A. Mejías in the Spring of 2023 at the St. George's Golf Course, Bermuda. Bermuda white-eyed vireos are the last remaining endemic landbird species on Bermuda, but remain common in woodlands, thickets, and gardens, islandwide. Miguel A. Mejías and David R. Wilson studied 'The relationships of breeding stage to daytime singing behaviour and song perch height in Bermuda white-eyed vireos Vireo griseus bermudianus'. The study suggests that suggests that male vireos increase their conspicuousness to prospecting females by increasing song production and song perch height, and that they sing during the breeding and non-breeding seasons to defend year-round territories. 

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 and territory defence hypotheses. We compare song production 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. Song production did not differ significantly between the breeding and non-breeding seasons, but, within the breeding season, males without nesting duties sang significantly more songs than males with nesting duties. 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 song production 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.

The figure above shows the number of discrete songs produced during 15-min recording sessions of male Bermuda vireos during six breeding stages: 1) no nesting duties, 2) nest building, 3) egg stage, 4) nestling care, 5) fledgling care, and 6) non-breeding. For more details see the original article.

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