Breeding site fidelity is lower in polygamous shorebirds and male-biased in monogamous species

Sex-bias in breeding dispersal is considered the norm in many taxa, and
the magnitude and direction of such sex-bias is expected to correlate with
the social mating system. We used local return rates in shorebirds as an
index of breeding site fidelity, and hence as an estimate of the
propensity for breeding dispersal, and tested whether variation in site
fidelity and in sex-bias in site fidelity relates to the mating system.
Among 111 populations of 49 species, annual return rates to a breeding
site varied between 0–100%. After controlling for body size (linked to
survival) and other confounding factors, monogamous species showed higher
breeding site fidelity compared to polyandrous and polygynous species.
Overall, there was a strong male bias in return rates, but the sex-bias in
return rate was independent of the mating system and did not covary with
the extent of sexual size dimorphism. Our results bolster earlier findings
that the sex-biased dispersal is weakly linked to the mating system in
birds. Instead, our results show that return rates are strongly correlated
with the mating system in shorebirds regardless of sex. This suggests that
breeding site fidelity may be linked to mate fidelity, which is only
important in the monogamous, biparentally incubating species, or that the
same drivers influence both the mating system and site fidelity. The
strong connection between site fidelity and the mating system suggests
that variation in site fidelity may have played a role in the coevolution
of the mating system, parental care, and migration strategies.