Incubation Schedules of Four Species of Calidridine Sandpipers at Barrow, Alaska

Norton, David

Incubation by four species of calidridine sandpipers at Barrow, Alaska, was analyzed by telemetric nest temperature recordings and by direct observation during three field seasons. In the Pectoral Sandpiper, Calidris melanotos, only the female tends the nest, whereas both sexes share in incubation in the Dunlin, C. alpina, Baird's Sandpiper, C. bairdii, and the Semipalmated Sandpiper, C. pusilla. Both the single-sex incubation system of melanotos and the two-sex system of the other three species must be organized so that embryos within each clutch develop and hatch simultaneously, despite low ambient temperatures and unpredictable weather. The salient features of incubation schedules among these sandpipers were found to include: 1) A rapid transition from desultory to nearly continuous incubation during the latter part of the egg-laying stage among the two-sex incubators (melanotos data lacking in laying stage); 2) Nest attentiveness of 85% by female melanotos, nest attendance of 96.5% by bairdii pairs, and 97.5% by alpina pairs, between laying and hatching (pusilla data lacking from this state); 3) A strong diurnal periodicity in incubation parameters of melanotos, weaker periodicity among alpina and bairdii pairs, which rhythms functionally afforded more constant covering of all nests during colder hours of the 'night'(18:00-06:00) despite the continuous daylight at Barrow; 4) Only minor changes in incubation schedules for all species over the period between laying and hatching, but profound and rapid schedule modifications between laying and incubation stages, and between incubation and hatching stages; 5) A weak correlation between adverse weather conditions and incubation constancy among alpina and bairdii, which became highly pronounced (although difficult to measure) as critical hatching processes began; 6) Optimization and synchronization of hatching time by stimuli largely controlled by adult behavior just prior to and during hatching.

Incubation Schedules of Four Species of Calidridine Sandpipers at Barrow, Alaska

Series