CLUTCH DESERTION AND RE-NESTING IN PIED FLYCATCHERS - AN EXPERIMENT WITH PROGRESSIVE CLUTCH REMOVAL

Clutch desertion and re-nesting are important components of fitness wh en predation is frequent. In nestbox populations however, nest predati on and desertion are rare but can be studied by experimental manipulat ions. We experimentally reduced clutches of pied flycatcher, Ficedula hypoleuca, by removing one egg per day until desertion occurred. The s ize of the clutch at desertion and whether females re-nested or not we re used as measures of the female response. Of the deserting females, 74% re-nested in our study area. Re-nesting frequency was correlated w ith date but not with the size of the clutch laid. The majority of the non-re-nesting females deserted empty nests, while the majority of re -nesting females deserted one egg. Clutch size at desertion was not co rrelated with the size of the clutch laid nor with laying date; it was smaller than the size predicted by an optimality analysis of the valu e of both the current (deserted) and the replacement clutch. For the r e-nesting females, there was a negative correlation between fledging r ate of the replacement clutch and the size of the clutch at desertion. Our predictions, made under the hypothesis that desertion and re-nest ing are adaptive behaviours, were partly supported by the data; we exp lain the discrepancy by the constraint of searching for a new nest sit e or mate for re-nesting. (C) 1997 The Association for the Study of An imal Behaviour.