Prey Detection in Two Tit Species, Parus ater and P. cristatus

Authors


KLIVV, Savoyenstraße 1 A, A-1160 Wien, Austria.

Abstract

We studied the prey-detection response of two related tit species (Parus ater, coal tit, and P. cristatus, crested tit) which occur in similar habitats and which are separated by microhabitat use and mode of locomotion. Specifically, we tested whether the two species differ in their ability to detect cryptic prey, with the hypothesis that coal tits perform better because of their longer stays in microhabitat patches. We expected that interspecific differences and the flexible responses within species to different levels of prey crypticity both depend on search intensity. In the experiments, tits had to forage in four different prey conditions: conspicuous + small, conspicuous + large, cryptic + small, and cryptic + large. Capture success, the time needed to detect prey, and stare duration were measured. Both species were less successful with cryptic than with conspicuous prey and did worst with small and cryptic prey. They also needed more time for detection and stared longer when prey was cryptic. When prey had been overlooked, preceding stare durations were shorter than those ending in successful searches. There were clear differences between the species in performance, with the crested tit doing worse. Coal tits, on average, were more successful in detecting prey, returned less frequently to already emptied patches, detected prey faster and yet they stared more briefly. The within-species results support current notions on predator search, but the differences between species cannot be explained with the same mechanisms. We discuss these findings in the context of the foraging ecology of these species and conclude that crested tits use different cues to detect prey and/or search a larger area per unit time.

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