Seasonality of Clutch Size Determination in the Kestrel Falco tinnunculus: An Experimental Approach

Abstract

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The Role of Prolactin in the Regulation of Clutch Size and Onset of Incubation Behavior in the American Kestrel

“…In the blue tit Parus caeruleus (Haywood, 1993a) and European kestrel Falco tinnunculus (Beukeboom, Dijkstra, Daan, and Meijer, 1988), the time (from clutch initiation) at which eggs in the nest disrupt follicular growth is positively correlated with clutch size. Porter (1975) found similar results in American kestrels, suggesting that females producing small clutches are more sensitive to stimuli from eggs in the nest and therefore respond earlier than females producing large clutches.…”

Family Planning in the Kestrel (Falco Tinnunculus): the Proximate Control of Covariation of Laying Date and Clutch Size

“…We have elsewhere provided evidence that this decline reflects the variation in individual females laying at different dates in different years . (KRAPU, 1981), American coot (ALISAUKAS & ANKNEY, 1985), mute swan (REYNOLDS, 1972), pied flycatcher (BERNDT & WINKEL, 1967), tengmalm's owl (KORPIMXKI, 1987), sparrowhawk (NEWTON, 1986), jackdaw (R6ELL, 1978, carrion crow (YoM-Tov, 1974), long-eared owl (%VgNANDTS, 1984), ural owl (PIETI: 4INEN et al, 1986) and kestrel (BEUKEBOOM et al, 1988).…”

Responses of Female Burrowing Owls to Alterations in Clutch Size: Are Burrowing Owls Determinate or Indeterminate Egg-Layers?

“…In some species, females will lay substantially more than one replacement egg, provided that the removals begin with the first egg laid (Brockway 1968, Gilbert et al 1983, Rohwer 1984, Frumkin 1988, Arnold and Rohwer 1991. Eurasian Kestrel (Falco tinnunculus) females, for instance, lay additional eggs when their clutch size is reduced early in laying, but only if the removals are initiated before the females start spending half of their time incubating (Beukeboom et al 1988, Meijer 1990. Often prolactin levels steadily increase as the female spends more time incubating, and thus prolactin may proximately regulate clutch size by suppressing the growth and development of additional ovarian follicles (Lea et al 1981, El Halawani et al 1984, Hall et al 1986, Zadworny et al 1989, Meijer 1990 Figure 1.…”

“…This information was useful in establishing whether the time interval from clutch manipulation to the laying of the last egg was sufficiently long for a female to be able to respond to experimental egg removal or addition. In other avian species, final clutch size is determined days prior (typically 3-5 d) to the laying of the last egg (Haftorn 1985, Beukeboom et al 1988, Meijer 1990. To the best of our knowledge, there is no published information describing the mechanisms that regulate the timing of final clutch size determination in Burrowing Owls.…”