The effect of foraging ecology on the onset of dawn song for passerine species
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Passerine birds have a burst of energetic singing prior to sunrise during the breeding season, called the dawn chorus. In this thesis, I examine how interspecific differences in foraging ecology can explain the scheduling of dawn singers, by investigating how diet choice and availability and foraging adaptions are linked to the onset of dawn song. In this thesis, data from several published studies have been combined in order to gain new insights of bird ecology related to dawn song, with a focus on foraging behaviour and diet. The arguments are gradually built through several questions, using sound methods for data analysis. Each question gathers current knowledge from available research, and combines it into new insights of the field. In order to explore how feeding ecology of birds is linked to the scheduling of dawn song, a systematic literature search was performed to collect data on dawn choruses, and morphological, ecological and dietary information available for the bird species participating in the choruses. The trends have been explored for both temperate and tropical areas. The differences in absolute eye size, dietary trends, prey attack manoeuvers and foraging heights for early- and late-singing European and North American birds reveal that early-singing birds could take advantage of the nocturnal active prey species available during dawn, have the ability to catch them, and therefore start profitable foraging during dawn. I suggest that foraging ecology is an important factor determining the scheduling of the dawn chorus in temperate areas. The factors affecting the timing of dawn song appear to be latitude dependent, and foraging ecology seems to be a stronger factor for temperate than for tropical choruses.
PublisherThe University of Bergen
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