Communication and reproductive behaviour of the Bermuda White-eyed Vireo (Vireo griseus bermudianus) and other vireonids

Mejias, Miguel Alberto (2022) Communication and reproductive behaviour of the Bermuda White-eyed Vireo (Vireo griseus bermudianus) and other vireonids. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Vocal displays are one of the primary ways songbirds communicate. The drivers of bird song diversity, how it might promote speciation through reproductive isolation, and their role in mate attraction and territory defence, can be better understood by studying variation within avian families. I studied the structure and function of songs in Vireonidae, and the nesting and singing behaviour of the Bermuda White-eyed Vireo (Vireo griseus bermudianus). I found that Vireonidae song traits have phylogenetic signal, with song traits being more similar among closer relatives than among distant relatives. I also found that species with smaller bodies and bills produced higher peak frequencies than bigger species. Using song playback, I tested whether male Bermuda Vireos, which are allopatric to all other vireonids, perceive this song diversity and adjust their response strength according to acoustic similarity that is related to phylogenetic history. Bermuda Vireos exhibited more vocalizations and speaker interactions during playbacks of closer relatives versus distant relatives, and to songs with more acoustic similarity to Bermuda Vireos. After studying their nesting cycle, I learned that breeding pairs in this subspecies sometimes remain paired for at least four years, and that they build small, cup-shaped nests in native and introduced trees. During February – September, both sexes performed nest building (N = 13, 5 ± 3 days; mean ± SD), incubation (11, 14 ± 2 days), nestling care (6, 11 ± 2 days), and fledgling care (5, 41 ± 12 days). Nest predation from introduced predators caused most nest failures. I then quantified their song rates during these nesting stages to understand how song functions in mate attraction, territory defence, and nest predator avoidance. Despite singing year-round, males during the breeding season without nesting duties sang more than males with nesting duties. Males sang less during the nestling stage, when predation was highest. Song perch height was higher during the breeding season than the non-breeding season, among males without nesting duties compared to males with nesting duties, and when males produced discrete songs rather than rambling songs. My doctoral thesis sheds light on factors shaping bird song structure, how receivers perceive these signals, and how males use them to communicate their breeding status and territory ownership.

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