A tropical bird with a short breeding season and high rates of nesting success: the breeding ecology of the Star-throated Antwren (Rhopias gularis: Thamnophilidae) in subtropical Brazil

Abstract

We studied nesting in marked pairs of Star-throated Antwrens (Rhopias gularis) over 3 years to examine whether breeding traits in subtropical Brazil are more similar to temperate patterns of breeding than is typical of the patterns observed within the mostly tropical Thamnophilidae. This Antwren is socially monogamous and permanently territorial, as are all Thamnophilidae, and has a long incubation period (18 days) and shorter nestling period (13 days). Its breeding season is relatively short (<4 months) and nesting success high (36%) compared with those traits of tropical antbirds. Daily nest- survival rate (DSR) during incubation was fairly low and declined throughout the breeding season, whereas DSR was greater and constant during the nestling period. Thus, early nests were more successful and, after hatching, nestlings had a very high probability of fledging (up to 90%). Only males built nests, which can be reused, apparently reducing reproductive demand on females. Pairs did not re-nest in the same season after a successful nesting attempt. Average fecundity was 1.0 ± 0.3 fledglings female⁻¹ year⁻¹, similar to that of tropical thamnophilids. We argue that the timing of breeding and reproductive effort are adjusted to reduce breeding costs in a subtropical climate, resulting in a unique combination of life-history traits for a bird of tropical origin.

Additional keywords:

• behavioural ecology
• passerines
• population
• productivity
• South American birds