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Fasting of Captive Shearwaters

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Fasting of Captive Shearwaters.--Richdale (Condor, 4i, 1945:SS) states that for young Sooty Shearwaters (Pufiinrus griseus) intervals between feedings are as long as ten days, and correlates this with the sometimes very distant feeding grounds of the parents. Lockley (British Birds, 23, 1930: 202-218) speaks of an enforced 12-day fast of young Manx Shearwaters (&&zus Pafi~ @&Us) just before taking flight from the breeding grounds. With this rather remarkable fasting ability in mind, we brought two young Wedge-tailed Shearwaters (Pufinus cuneatus pacificus) about five weeks old back to the University of Hawaii campus from one of Oahu’s small offshore islands. They were kept in separate compartments of a heavy, partly dirt-filled crate under conditions roughly comparable to their natural burrows, and their growth, vitality, and loss of weight during fasting were observed.

Neither food nor water was given to the two shearwaters for 21 days. During that time both birds lost 52 per cent of their original weight (470 and 466 grams reduced to 226 and 222 grams, respectively). The rate of loss during the first week or ten day< was comparable to, although somewhat slower than, that in birds studied by Richdale (op. cit.: 59). The rate of loss in the captive birds slowed down markedly after approximately the first ten days, for both lost an average of 155 grams during the first ten days as compared to 83 grams in the last ten days. Ths change was visibly correlated with lessening activity and vitality.

Growth of the captive birds was considerable in spite of continued loss of weight. The wingspread increased over three inches and the length of rectrices over 1% inches in both birds during their fasting period. The rate of growth appears to be closely comparable to that found by Richdale except during the last five days of captivity when growth was much slower or nearly stopped. One of the captive birds became noticeably quiet and weak during the last week, but the second only slightly so. Both quickly became normally energetic and altercatious when feeding was begun. The birds were returned to their offshore island shortly after this and exchanged with two well-grown young which were put in empty burrows. On the basis of Lockley’s work and the evidence of the present study, it was hoped that the displaced birds would be able to complete maturation and take flight without further feed&&--FRANK RICHARDSON, University of Nevada, Rena, Nevada, November 5, 1948.

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