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

Abstract

Spotted Sandpipers are unusual among animals in that a female's annual reproductive effort is regulated primarily by her ability to obtain mates. Males provide most of the parental care in this species. We recorded data on the abundance of food, and on the timing, number, and size of eggs laid by marked females over a 9—yr period on an island in central Minnesota, USA. The onset of egg—laying varied from year to year in association with the abundance of flying insects early in the season. After laying began, there was no relationship between food abundance and the number of size of eggs laid, the time taken to produce a clutch, or the intervals between clutches. The rate of egg—laying per female was affected, however, by rates of nest predation and by the operational sex ratio, which became increasingly female—biased over the season. Females ceased laying eggs in early July, even in years when food and mates were still available. We conclude that nutrient availability acts as a proximate factor in determining the onset of breeding, and that it may have been ultimate factor causing cessation of egg—laying. Within the season, however, the reproductive rate of individual females is primarily determined by competitive interactions with other females for males. Thus both intra and intersexual selection have important effects on fitness in this species.

Lifetime reproductive success in the spotted sandpiper (Actitis macularia) : sex differences and variance components

“…Multiple mates buffer the effects of nest loss on variance in female LRS. Given time constraints of a single breeding season, female spotted sandpipers theoretically are capable of producing a maximum of 4-6 clutches (Lank et al 1985). During this study, just one female produced five clutches in a season, and none produced six.…”

Male choice and sperm competition as constraints on polyandry in the red-necked phalarope Phalaropus lobatus

“…In the results presented here there was little to suggest that female P. lobatus were under energetic stress as a result of laying a clutch. Implicit in the energetic constraint argument is the assumption that energy reserves are depleted as a result of laying a clutch: in a review of the available evidence Erckmann (1983) concluded that female waders do not appear to use reserves in the production of eggs (see also Lank et al 1985;Reynolds 1987). The conclusion of this and other studies of phalaropes (Erckmann 1983;Reynolds 1987;Colwell and Oring, unpublished), that female phalaropes are not limited energetically, begs the question of why, after laying a clutch for a male, do female phalaropes not lay a second clutch and care for it themselves, as do some other species of waders (e.g.…”

Factors regulating annual mating success and reproductive success in spotted sandpipers (Actitis macularia)

“…In 1986 and 1987 hormonal studies that might have affected MS or RS were conducted; therefore, these years were omitted from this analysis. A detailed description of the study area and an account of the population biology of spotted sandpipers can be found elsewhere (Maxson and Oring 1980;Lank 1982, 1986;Oring et al 1983;Lank et al 1985).…”

“…Several factors contributed to this pattern. Whereas female MS ranged from 1 to 4 or 5 annually (Lank et al 1985), parental investment patterns limit males to at most one successful clutch annually. Male RS is limited to a maximum of 4 chicks, whereas females might produce up to 20 (Oring et al 1983;Lank et al 1985).…”