Abstract
Birds breeding in cold environments regularly have to interrupt incubation to forage, causing a trade-off between two mutually exclusive behaviours. Earlier studies showed that uniparental Arctic sandpipers overall spend less time incubating their eggs than biparental species, but interspecific differences in size and ecology were potential confounding factors. This study reports on a within-species comparison of breeding schedules and metal egg temperatures in uni- and biparental sanderlings (Calidris alba) in Northeast Greenland in relation to ambient temperature. We recorded incubation schedules with nest temperature loggers in 34 sanderling clutches (13 uniparentals, 21 biparentals). The temperature of a metal egg placed within the clutch of 17 incubating birds (6 uniparentals, 9 biparentals) was measured as an indicator of the heat put into eggs. Recess frequency, recess duration and total recess time were higher in uniparentals than in biparentals and positively correlated with ambient temperatures in uniparentals only. Uniparental sanderlings maintained significantly higher metal egg temperatures during incubation than biparentals (1.4°C difference on average). Our results suggest that uniparental sanderlings compensate for the lower nest attendance, which may prolong the duration of the incubation period and negatively affect the condition of the hatchlings, by maintaining a higher heat flux into the eggs.
Highlights
Incubation is an energetically demanding phase of avian reproduction [1,2,3] and this is so in High Arctic breeding birds of relatively small size that lay their eggs in open nest cups on the ground, often only a few centimeters above the permafrost [4,5]
Ambient temperatures in the High Arctic are usually far below the minimum of 26uC that is required for embryonic development [6], but when incubating adults forage they necessarily expose their clutch to ambient temperatures unless a partner takes over
We investigated two possible ways for uniparentals to enhance embryo development: (1) by adjustments of the incubation schedules in relation to ambient temperatures, and (2) by regulating egg temperature
Summary
Incubation is an energetically demanding phase of avian reproduction [1,2,3] and this is so in High Arctic breeding birds of relatively small size that lay their eggs in open nest cups on the ground, often only a few centimeters above the permafrost [4,5]. Ambient temperatures in the High Arctic are usually far below the minimum of 26uC that is required for embryonic development [6], but when incubating adults forage they necessarily expose their clutch to ambient temperatures unless a partner takes over. This results in a conflict between the demands of incubating adults and those of their offspring [7]. When spending much time away from the nest, such birds run the risk of slowing down or even ceasing embryonic development [11]
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