Rare insights into intraspecific brood parasitism and apparent quasi–parasitism in black–capped chickadees

K A Otter,B W Murray,C I Holschuch,K T Fort

doi:10.32800/abc.2011.34.0023

Abstract

Genetic analysis of passerine birds often finds evidence of extra–pair copulations within species, but genetic evidence of intraspecific brood parasitism (IBP) and quasi–parasitism (Q–P) are relatively rare. Further, it is even rarer for genetic patterns that might indicate quasi–parasitism (resident male sires offspring through extra–pair copulations, and allows the female to lay these within the male’s nest) to be coupled with observational evidence of this behavior. In this paper, we report behavioral observations surrounding the nest of black–capped chickadee, one of the few species in which both IBP and Q–P have been detected through a genetic analysis. These were later confirmed to have young genetically mismatched with both attending parents, as well as mismatched with the attending female but sired by the attending male. The behavioral patterns associated with this nest are contrasted with the two previously reported cases of IPB/Q–P in this species, and suggest that rare ‘detection’ of quasi–parasitism may be explained by converging patterns of extra–pair behavior and the rarer strategy of intraspecific brood parasitism.

Highlights

Intraspecific brood parasitism (IBP) –eggs/nestlings appearing within a nest though they are not genetically related to either the resident male and female– commonly occurs in some bird taxa that have precocial young, such as ducks and coots
Despite numerous studies in the past decade, mixed parentage in most passerines results from extra–pair copulations rather than from brood parasitism by conspecific parents not associated with the nest (IBP), or through quasi–parasitism (Griffith et al, 2004)
We report on the behaviour observed at a nest of black–capped chickadees Poecile atricapillus (one of the few species in which genetic patterns of quasi–parasitism have been reported (Otter et al, 1998)) in which IBP was suspected, and later genetically confirmed

Summary

Introduction

Intraspecific brood parasitism (IBP) –eggs/nestlings appearing within a nest though they are not genetically related to either the resident male and female– commonly occurs in some bird taxa that have precocial young, such as ducks and coots. IBP may be a mixed, sequential strategy, such as occurs in Starlings (Sturnus vulgaris) where unmated, recently–arriving females parasitize conspecifics during the period in which they themselves are settling, and lay their own clutches normally once they have acquired a nest site (Sandell & Diemer, 1999). In this manner, the female supplements the fecundity of her own nests by adding offspring in other nests, ecologically equivalent to the gains made by males pursuing extra–pair copulations. IBP may be both a strategic and opportunistic behaviour, such as when females in colonial species in close proximity of each others’ nests occasionally egg–dump to take advantage of both mixed strategies and bet–hedging strategies (Alves & Bryant, 1998)

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Conclusion