Does competition for nests affect genetic monogamy in Cory's shearwaterCalonectris diomedea?

Abstract

Most bird species are socially monogamous. However, extra‐pair copulations (EPCs), resulting in extra‐pair paternity (EPP), commonly occur. EPCs should allow females to adjust social mate choice and allow males that fail to obtain a nest a chance to avoid missing a breeding season, especially when poor nest supply constrains social mate choice. Procellariiformes (albatrosses and petrels) are socially monogamous seabirds which seldom divorce, even when nest availability constrains social mate choice. In Cory's shearwater Calonectris diomedea, a burrow‐nesting petrel, two studies conducted in the Mediterranean, where competition for nests is weak, detected no EPP. EPP remains to be investigated at localities where competition for nests is much stronger, such as Vila islet, Azores archipelago, Atlantic Ocean. We conducted a genetic (microsatellites) study over two successive years on Vila, involving the breeding pairs of the same 65 nests each year and their single chick. EPPs occurred each year, the overall rate being 11.6%. Coupling genetic analyses to a 7‐year demographic survey provided additional data on pair bonds and competition for nests. Overall, cuckoldry was unrelated to divorce, nest density and inbreeding avoidance, but was more frequent when the social male was small. Nest changes were more costly for males than for females, and some apparently unpaired males attempted to dislodge social males during within‐pair copulations. These results are compatible with the existence of a link between poor nest availability and EPP and confirm that even species considered strongly monogamous can adopt flexible mating strategies.

New haematological data in Cory's shearwater,Calonectris diomedea(Aves, Procellariiformes)

“…Molecular sexing was conducted using blood samples from three other Cory's shearwaters previously sexed from vocalisations as controls, and had previously been validated on another Cory's shearwater colony from the Azores, where 60 males and 58 females were sexed both from calls and molecular sexing: the results from the two methods were 100% congruent (Bried et al 2010). …”

Chemical labels differ between two closely related shearwater taxa

“…Although samples from both species were collected in different months, they were all sampled during the reproductive season, mostly during incubation. The birds from the Salvage Islands (8 females and 8 males) were sexed using molecular methods developed by Fridolfsson and Ellegren (), and those from the Azores were sexed from vocalizations (9 females and 8 males), which are sexually dimorphic (Bried et al ).…”

Poaching vs. patrolling: effects on conservation of Cory’s Shearwater Calonectris diomedea borealis colonies

“…Environmental variability in reproduction and mortality was modelled to be concordant. We assumed that Cory’s Shearwaters were long-term monogamous birds (Swatschek et al 1994; Rabouam et al 2000; but see Bried et al 2010). Age of first breeding for females and males was set at four (see Jenouvrier et al 2008), and maximum age of reproduction at 25 because, although it is known that shearwaters show great senescence (see e.g.…”