Food provision to nestlings in the Hoopoe Upupa epops: implications for the conservation of a small endangered population in the Swiss Alps

In an attempt to recognize the possible ecological causes of the decline of a population of Hoopoes Upupa epops in the Swiss Alps, we collected data o n resource exploitation. The prey provisioned to nestlings by parents was i nvestigated at four breeding sites using photographs (n = 4353, 80% of whic h enabled prey identification). Molecrickets Gryllotalpa gryllotalpa and Le pidoptera (larvae and pupae) were dominant in nestling diet (93% frequency; 97% biomass). Although Molecrickets were provisioned less frequently (26%) than Lepidoptera (67%), they represented 68% of the total biomass (vs 29% for Lepidoptera). There was an overall negative relationship between the pr oportion of Molecricket biomass in the diet and the parents' feeding rate, whereas a comparison between broods showed that a higher provisioning activ ity did not lead to an increase in the biomass supplied to the chicks. A di et based on Molecrickets therefore appears to be energetically advantageous . As Molecrickets are a traditional prey of Hoopoes in central Europe, this might be relevant to other populations. In the study area, Molecrickets oc cur only on the intensively cultivated plain, whereas the majority of Hoopo e pairs nest at various altitudes on the foothills adjacent to the plain as the latter provides at present almost no suitable nesting sites. Hoopoes b reeding higher up on the foothills seem to experience greater provisioning costs and have, on average, lower breeding success. Providing nest sites on the plain is the main conservation measure proposed for the local Hoopoe p opulation. Further attention should also be paid to Molecrickets as these m ay be crucial for Hoopoes.