Nest Size Matters: Common Cuckoos Prefer to Parasitize Larger Nests of Oriental Reed Warblers

Abstract

BackgroundAvian brood parasites leave parental care of their offspring to foster parents. Theory predicts that parasites should select for large host nests when they have sufficient available host nests at a given time. We developed an empirical experimental design to address this hypothesis by studying nest choice of common cuckoos (Cuculus canorus) among nests of its Oriental reed warbler (Acrocephalus orientalis) hosts.ResultsWe presented two groups of experimental nests: 1) nest dyads comprise one large and one small artificial nest from reed leaves, and 2) nest triads tied together use the modified old own warbler nests including enlarged, reduced and medium sized nests to elicit parasitism by common cuckoos. We predicted that cuckoos prefer larger nests over medium sized ones, and over the smallest nest. Our experimental findings show that common cuckoo females generally prefer large nests over medium or small sized nests. Furthermore, experiments showed that cuckoo parasitism was significantly more common than in previous studies of the same warbler population.ConclusionsOur results implying that larger, taller and more exposed host nests effectively increased the probability of cuckoo parasitism.

Experimental evidence that cuckoos choose host nests following an egg matching strategy

“…If this would be the case, cuckoos might benefit from selecting host nests with blue eggs (compared with pink eggs) because their chicks would be raised in a better environment and thus have a higher probability of fledging [58]. This is in line with the ‘optimal egg-laying strategy’, which proposes that when there are plenty of nests available in a given host population, female cuckoos should choose the nest of the highest-quality hosts [40,59]. However, redstarts laying blue eggs did not outperform individuals laying pink eggs in terms of egg volume, clutch size and the proportion of nests that were successful (i.e.…”