High begging intensity of great spotted cuckoo nestlings favours larger-size crow nest mates

Abstract

In nests of birds parasitized by a larger non-evicting brood parasite, host chicks typically are at disadvantage in competing for food and often starve. However, when host chicks are larger, they may benefit from the presence of the parasite, which contributes to the net brood begging signal but cannot monopolize the food brought to the nest. Here, we show that, despite a higher begging intensity, great spotted cuckoos (Clamator glandarius) did not outcompete larger size carrion crow (Corvus corone corone) nestlings. Furthermore, cuckoos’ exaggerated begging allowed crow nest mates to decrease their begging intensity without negative consequences on food intake. Assuming an energetic cost to chicks of begging intensely, our results suggest that crow chicks sharing the nest with a cuckoo may obtain an advantage that should be weighed against the loss of indirect fitness due to parasitism.