Mating system and nesting biology of the Red‐necked Phalarope Phalaropus lobatus: what constrains polyandry?

Open Access
Publisher Website
Google Scholar
Abstract
In this five‐year study of Red‐necked Phalaropes on the coast of Hudson Bay, Canada, only 8% (5/59) of females were polyandrous. Seventy‐five percent were monogamous, and 17% did not obtain mates. All males obtained mates readily. To understand the low incidence of polyandry in this sex‐role reversed, non‐territorial mating system, aspects of the pair bond, nesting biology, and size and plumage dimorphism were examined.Pair bonds lasted an average of 11 days and ended as soon as the clutch was completed. Polyandrous females initiated their second nests only seven days later. Since in most years nest initiation for the population as a whole spanned three weeks, there was ample time for multiple clutches. Energetic constraints may have played a limited role in constraining polyandry, but many females that had previously laid clutches courted incubating males or harassed pairs.The major factor limiting polyandry appeared to be availability of mates. Because phalaropes generally breed in habitats that are less defensible than those of other role‐reversed shorebirds, they are less able to monopolize males in populations with equal sex ratios. Sexual size dimorphism is correspondingly smaller than in territorial role‐reversed shorebirds, although plumage variation between and within sexes in this study was strong (and invariant with age). Thus, despite the phalaropes' role‐reversal, the evidence indicates that monogamy may predominate, with sexual selection driven by the ability of females to produce second clutches opportunistically when receptive males are available.