Reproductive decisions in the kestrel. Falco tinnunculus. A study in physiological ecology.

The number of eggs birds lay (clutch size) varies between species. Such variations have been considered, since Lack (1954), as evolutionary adaptions to maximize the number of offspring. Clutch size also varies within species (Klomp 1970), depending on age of the female, latitude, time of year, temperature, feeding conditions, etcetera. In many singlebrooded species there is a decline in clutch size with progressive time of laying (laying date). Such variations in laying date and clutch size ask for an evolutionary or functional and for a physiological explanation, in other words: which ultimate factors in de environment make reproductive patterns adaptive and what are the proximate factors triggering the reproductive decisions? This thesis concerns the second question. It exploits the highly predictable decline in clutch size of the European Kestrel Falco tinnunculus to tackle the problem: how determines a bird her date of laying and number of eggs? ... Zie: Summary