Kl. Wiebe, INTRASPECIFIC VARIATION IN HATCHING ASYNCHRONY - SHOULD BIRDS MANIPULATE HATCHING SPANS ACCORDING TO FOOD-SUPPLY, Oikos, 74(3), 1995, pp. 453-462
The adaptive significance of hatching asynchrony in birds has been the
subject of considerable controversy Numerous hypotheses have been pro
posed to explain hatching patterns, but few of these account for intra
specific variation in those patterns. I developed a mathematical model
of facultative manipulation of hatching based on the brood reduction
hypothesis and the assumption that hatching patterns have different fi
tness payoffs in good and bad food-years. I compared the productivity
of facultative manipulation to the productivity of a single, fixed, ha
tching span. When food resources during the nestling period are partly
predictable from those during the prelaying period, facultative manip
ulation appears advantageous in many types of environments. Predictabi
lity of food resources depends on the nature of the food supply, espec
ially temporal patterns of abundance over the long- and short-terms. C
orrelation analyses showed that the small mammal prey of the American
kestrel, a bird which practises facultative manipulation of asynchrony
, were quite predictable during the summer. Generation times of a spec
ies in relation to the timing of fluctuations in food resources map al
so influence whether or not facultative manipulation evolves.