Organisms should respond more aggressively towards species perceivedas a danger to their offspring, but intensity of defence may be gauged bythe value of current offspring weighed against the value of future reproductiveopportunities. We tested whether defensive responses of nestingreed warblers (Acrocephalus scirpaceus) are the result of an interactioneffect between the type of stimulus confronted and the value of thewarbler’s nesting attempt. We quantified the ability of reed warblers todiscriminate among brood parasites, nestling predators and non-threateningspecies at different stages of the breeding cycle. We also determinedwhether variables that influence the value of offspring, such astime of season, size and age of clutch or brood, and time of day andnumber of visits to the nest, explain variation in the intensity of defencerecorded during the egg and nestling stages. Responses to the threestimuli differed significantly, as reed warblers consistently directed theirmobbing calls and attacks towards parasites, whereas they were lessconspicuous when confronted with models of predators. Reed warblersmodulated their responses towards each stimulus in accordance withthe threat each posed at a specific nesting stage, whereas they were notaffected by other variables relative to their reproductive potential. Thechurr call, however, was uttered independently of the stimulus, as it wastriggered by the mere presence of nestlings in the nest.
|Numero di pagine||11|
|Stato di pubblicazione||Published - 2010|
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