Abstrakt
Obligate avian brood parasites usually require longer and/or more parental care than host progeny and thus may have a detrimental effect on survival of host parents. Many hosts of brood parasites are long-distance migrants, spending significant proportions of annual cycles at different sites around the world, which makes correct timing of particular events within these cycles of utmost importance.
Nevertheless, conditions in a given phase of the annual cycle may influence the timing of the following phases via carry-over effects. Here, we explored whether great reed warbler (Acrocephalus arundinaceus) parents fostering a brood-parasitic common cuckoo (Cuculus canorus) were delayed on departure from the breeding site and arrival at the wintering sites compared to the parents caring for own nestlings.
Additionally, we tested whether the parents with nestlings hatched later in the season set out for autumn migration and arrived at the wintering sites later than the parents with nestlings hatched earlier in the season and whether female parents lagged in time behind male parents during autumn migration. We found that the parents fostering the common cuckoo were delayed neither on departure from the breeding site nor on arrival at the wintering sites compared to the parents rearing own nestlings.
Moreover, there was no effect of hatching date and parent sex on the timing of autumn migration. Future studies may rather focus on tracking female parents which could be more affected by the care for a brood parasite than male parents.
Future researchers may also strive to monitor post-fledging survival of young, as increased mortality of either the brood-parasitic or host fledglings could affect the end of host parental care and thus also the timing of host autumn migration.