Data for Effects of climate and host migration strategy on egg-laying dates in an avian brood-parasite

Abstract Climate change is causing temporal shifts in the reproductive phenology of interacting species. Such shifts can disrupt parasite-host dynamics, particularly if the parasite’s reproduction is dependent upon the host’s reproductive cycle. In avian brood parasitism, the brood parasite utilize the host for reproduction. In response to climate change, several bird species subjected to brood parasitism have advanced their breeding onset. However, whether avian brood-parasites can track their hosts changing phenology remains unknown. Using a cross-continental, long-term dataset of brood-parasitism events by the common cuckoo Cuculus canorus at multiple locations across Europe consisting of more than 40 years from 1980-2021, we tested if the cuckoo has advanced its egg-laying, and how this relates to local temperature conditions and the migration strategy of the host. Moreover, we tested whether the cuckoo were able to adjust egg-laying tracking inter-annual changes in spring temperature. We found that the cuckoo has advanced its laying date over the study period by 1.2 days per decade (indicating a long-term response) where the host is a long-distance migrant, but tended to delayed egg-laying when the host is a resident or a short-distance migrant. By selecting locations with multiple parasitism records for a host species over several years, we found that the cuckoo advanced their egglaying more in years with increased spring temperature (indicating a short-term response). However, we found no support for an interaction between host migration strategy and inter-annual temperature variation. We therefore show that the cuckoo adjust timing of egg-laying both on a long-term scale (across the study period) and a short-term scale (inter-annual responses) independent of host migration strategy. Our results suggest that brood-parasites can adjust their reproductive phenology to environmental change, but that the magnitude of response also depends on life-history traits by the host species.