A comparative analysis of auditory perception in songbirds: Eurasian jays (Garrulus glandarius) and great tits (Parus major)

Abstract

In the field of comparative cognition, auditory perception has received less study than its visual counterpart, yet it confers important survival benefits. Accurate responses to auditory stimuli enable animals to react to or interact with the stimulus. Vocal communication between and within species allows appropriate responses to predators, enemies, kin and partners. Songbirds have often been studied due their impressive but varied vocal learning abilities. The main objective of this thesis is to further the understanding of how auditory perception relates to behavioural actions in songbirds. Chapter 1 provides an overview of auditory cognition, vocal learning and sociality in the two model species: Eurasian jay (Garrulus glandarius) and great tit (Parus major). Chapters 2-5 utilise several different auditory paradigms in Eurasian jays, focusing on caching, reasoning and recognition. Chapter 2 replicates an experiment to test whether jays conceal auditory information as a cache protection tactic, the findings differ from the original study. Chapter 3 investigates whether jays can use auditory cues to locate hidden rewards. Subjects perform this task accurately with visual cues, but not acoustically using either the ‘natural’ sounds of the food or an associated novel sound. This was highly variable per individual. Chapter 4 expands on this idea to identify if biologically appropriate ‘novel’ sounds inspire searching behaviour in the jays. Jays were found to search in one location more than another. Chapter 5 tests the hypothesis that Eurasian jays are capable of individual vocal recognition. Jays search more for partners when they hear their call, and display interest in kin, stranger and rook (Corvus frugilegus) calls but not in a neutral control call. Chapters 6 and 7 focus on how the auditory recognition of predators develops in great tits and whether great tit nestlings are able to recognise predatory calls directly. Nestlings in Chapter 6 recognise predatory calls, as well as various conspecific calls and use this information to adjust their begging and crouching responses to avoid detection. This effect increases with nestling age. Chapter 7 questions whether the responses to predatory auditory stimuli is learnt. Nestlings do not need to learn to respond to a predatory stimulus, they responded appropriately in the group without experimental manipulation. The implications of these findings are discussed in Chapter 8 in relation to the ontogeny, sociality and ecology of each species, and what these results contribute to our understanding of auditory cognition in the light of what is known about vocal learning and sociality.