Population Studies of the Polyandrous Spotted Sandpiper

Abstract

A color-banded population of Spotted Sandpipers (Actitis macularia) was studied over a 10-yr period on Little Pelican Island, Leech Lake, Minnesota. A total of 75 females and 107 males bred for 144 ♀ ♀ yr and 200 ♂ ♂ yr. The observed skew in the population sex ratio was due primarily to behavioral exclusion of inexperienced females. Density appeared to limit population size and productivity. Locally hatched chicks accounted for 31% and 40% of the breeding females in the final 2 yr. Females laid eggs for 1.35-2.06 males per year. Experienced females had significantly more mates, eggs, chicks, and fledglings than did inexperienced females. Locally hatched chicks accounted for 21% and 19% of the breeding males in the final 2 yr. Males mated with 1.0-1.4 females per year. Experienced males had more mates and received more replacement eggs than did inexperienced males; in contrast to females, however, inexperienced males had no less hatching or fledging success than did experienced males. Thirty-eight marked females and 16 marked males tried unsuccessfully to enter the population, and 6 females and no males were observed to be nonbreeders all season long. Of 1,142 eggs, 442 hatched and 256 fledged. Experienced birds returned to breed more often in subsequent years than did inexperienced ones (61% vs. 50%). Return rates of successful birds were consistently higher than those of unsuccessful birds, the difference decreasing with age. Young males appeared to be less site-faithful than were females and older males. Successfully breeding females lived an average of 3.7 yr. Relative to other scolopacids with multipurpose territories, the Spotted Sandpiper is considered a pioneering species that quickly and frequently colonizes new sites, emigrates in response to reproductive failure, breeds first at an early age, lives a relatively short time, lays many eggs per female per year, and has relatively low nest success.

Adult sex ratios in wild bird populations

“… Heavily skewed ASRs in threatened populations may represent one end of a general correlation between population trend or density and sex ratio, the mechanism of which is unknown (though it might be related to any of the following possibilities). Such a relationship has been documented in at least one globally threatened bird, the Seychelles Magpie Robin Copsychus sechellarum (Gerlach & Le Maitre 2001), and similar patterns have been noted in other species of birds (Oring et al . 1983, Fry et al .…”

“…1982). A number of other species demonstrate flexible mating systems that respond causally to ASR, including Spotted Sandpiper Actitis macularia (Oring et al . 1983), Kaka Nestor meridionalis (Greene & Fraser 1998), Lesser Spotted Woodpecker Picoides minor (Wiktander et al .…”

Augmenting Small Populations of Plovers: An Assessment of Cross‐Fostering and Captive‐Rearing

“…(Bunni 1959). In contrast, Spotted Sandpipers nest exclusively in vegetation adjacent to bodies of water and rear broods along the shorelines (Oring et al 1983). In general, Killdeer parents moved their broods over longer distances than did Spotted Sandpipers.…”

Mate and Nutrient Limitation of Egg‐laying in a Polyandrous Shorebird

“…Spotted Sandpipers have a resource-defense polyandrous mating system (Emlen and Oring 1977). An outline of their breeding behavior is given by Oring (1982: 70-73, and references therein), and demographic aspects of the study population may be found in Oring et al (1983). Three features of reproductive biology are relevant here.…”

“…Polyandry leads to the limitation and even exclusion of breeding by some females. Females in our population have bred with up to four males per season, averaging 1.66 mates per breeding female between 1973(Oring et al 1983. Polyandry is advantageous for females, at least on an annual basis, since the number of chicks fledged per year increases as the number of mates increases (Oring 1982).…”