AVIAN DAILY FORAGING PATTERNS - EFFECTS OF DIGESTIVE CONSTRAINTS AND VARIABILITY

被引:119
作者
BEDNEKOFF, PA
HOUSTON, AI
机构
[1] UNIV OXFORD, DEPT ZOOL, NERC, BEHAV ECOL UNIT, OXFORD OX1 3PS, ENGLAND
[2] UNIV OXFORD, EDWARD GREY INST, DEPT ZOOL, OXFORD OX1 3PS, ENGLAND
关键词
FORAGING; DAILY ROUTINE; DIGESTION; STARVATION; PREDATION; RESERVES;
D O I
10.1007/BF01237664
中图分类号
Q14 [生态学(生物生态学)];
学科分类号
071012 ; 0713 ;
摘要
Birds show a typical daily pattern of heavy morning and secondary afternoon feeding. We investigate the pattern of foraging by a bird that results in the lowest long-term rate of mortality. We assume the following: mortality is the sum of starvation and predation. The bird is characterized by two state variables, its energy reserves and the amount of food in its stomach. Starvation occurs during the day if the bird's reserves fall to zero. The bird starves during the night if the total energy stored in reserves and the stomach is less than a critical amount. The probability that the bird is killed by a predator is higher if the bird is foraging than if it is resting. Furthermore, the predation risk while foraging increases with the bird's mass. From these assumptions, we use dynamic programming techniques to find the daily foraging routine that minimizes mortality. The principal results are (1) Variability in food finding leads to routines with feeding concentrated early in the day, (2) digestive constraints cause feeding to be spread more evenly through the day, (3) even under fairly severe digestive constraints, the stomach is generally not full and (4) optimal fat reserve levels are higher in more variable environments and under digestive constraints. This model suggests that the characteristic daily feeding pattern of small birds is not due to digestive constraints but is greatly influenced by environmental variability.
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页码:36 / 52
页数:17
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