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

Abstract

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% and 100%. After controlling for body size (linked to survival) and other confounding factors, monogamous species showed higher breeding site fidelity compared with 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.

Consistent apparent adult survival and nest‐site fidelity of whimbrelNumenius phaeopusnear Churchill, Manitoba, Canada over a 40 year period

“…Whimbrels are generally faithful to their breeding sites (0.20 emigration rate; Ruthrauff et al 2021), though males tend to be more loyal to their breeding territory than females (Kwon et al 2022). Contrary to our expectations, however, inter‐annual dispersal distances in 2010 to 2014 did not differ between sexes, and overlapped with historical estimates of dispersal distances in 1973 to 1976 (Skeel 1983).…”

“…Because of recent increases in the rate of the whimbrel population decline, we first predicted that rates of apparent survival would be lower during our most recent study period. Additionally, other studies of monogamous shorebirds suggest that reproductive costs are higher in females, driven by the energetic costs of egg production (Brunton 1988), and that, in species with male‐defended territories, nest‐site fidelity is higher in males than females (Lishman et al 2010, Kwon et al 2022). Therefore, we also predicted that both apparent survival and nest‐site fidelity would be higher in males than females.…”

Breeding populations of Marbled Godwits and Willets have high annual survival and strong site fidelity to managed wetlands

“…We found small sexual differences in apparent survival with males having higher apparent survival than females in both species. Higher return rates or apparent survival among males are a common feature of shorebirds that are socially monogamous with a male‐territorial social system (Kwon et al, 2022; Oring & Lank, 1984; Sandercock & Gratto‐Trevor, 1997; Thompson & Hale, 1993), although no sex differences have been reported too (Groen & Hemerik, 2002; Ottvall, 2005). Mated pairs of shorebirds usually winter at separate nonbreeding sites but meet again at breeding sites (Gratto‐Trevor, 2011; Gunnarsson et al, 2004).…”

“…Large‐bodied shorebirds are often characterized by a “slow” life‐history strategy with low reproductive rates, delayed maturity, and high survivorship (Myers et al, 1987; Watts et al, 2015). Shorebirds with socially monogamous mating systems also tend to have strong fidelity to breeding sites and to mates (Kwon et al, 2022; Oring & Lank, 1984). Thus, population growth rates are likely to be more sensitive to factors that affect adult survival and breeding site fidelity than components of reproduction (Hitchcock & Gratto‐Trevor, 1997; Koivula et al, 2008; Ottvall & Härdling, 2005).…”

Carry-over Effects in Arctic-breeding Shorebirds: A Cross-species Perspective

“…Slower migration in birds travelling further may therefore reflect sex differences in fueling rates, potentially resulting from differences in bill length (Duijns et al, 2014). In many species, males winter further north, and are also the more territorial sex, with stronger selection for early arrival (Kwon et al, 2022). These traits may combine to explain the observed pattern between migration distance and arrival timing.…”