Bird Activity in the Continuous Daylight of Arctic Summer

Karplus, Martin

The activity cycles of three nesting species were studied briefly in the continuous daylight of arctic summer. The daily periods of rest were more closely correlated with the period of minimum light intensity than with temperature. Together with previous observations of synchronization of song with dawn and dusk in temperature regions, these observations point to the conclusion that the sleep-wakefulness cycle of birds is governed by the environmental light. 2. By comparing a robin nest studied in the arctic with those observed in temperate regions, it was found that the nestling period of the arctic young (9 days) was 4 days shorter than the average for 85 temperate-latitude broods (13.2 days). Further analysis suggests that the decrease in nestling period and the associated rise in the growth rate resulted from the greater number of hours per day during which food was supplied by the parents. The total number of feeding trips for the arctic nest was calculated to be about 1,225, only slightly less than the 1,340 feedings received by a comparable brood in Columbus, Ohio. 3. The observation of a shortened nestling period in one pair of birds indicates that a factor from which migrations derive their survival value is the more rapid growth of young possible in the north.

Bird Activity in the Continuous Daylight of Arctic Summer

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