Perception, Cognition, and Response: A Recognition Systems Analysis of Avian Egg Rejection

To claim and understand the uniqueness of any physical, chemical, or biological system, it is necessary to use the same set of approaches, tools, and analyses to probe other systems. Accordingly, to assess whether and how people are unique in their perceptual, cognitive, and behavioural skills and algorithms when making decisions, a parallel set of studies is required to examine how human and non-human animals would respond. This thesis provides a structured experimental analysis of each of the recognition system’s components; perception, cognition, and response; in the context of avian brood parasitism. The study species are several potential hosts of brood parasitic birds but an explicit aim of this work to provide a reference for future studies on how to probe the perceptual, cognitive, and response traits in non-verbal experimental paradigms, including non-hosts and working with people. Hosts of avian brood parasites represent a powerful experimental system in which to study well defined and evolutionarily relevant behavioural decision: brood parasitic birds lay their eggs in other nests and the costs of parental care and reduced reproductive success are borne by the hosts. Hosts, in turn, may reject costly parasitism by ejecting foreign progeny or deserting parasitized nests. The cues used by hosts to perceive, recognize, discriminate, and respond to foreign eggs have been well studied in a variety of avian host-parasite systems. How, in turn, the hosts’ sensory and cognitive processes receive, sort through, and determine the behavioural responses to these cues, remains mostly unclear. The main chapters of the thesis set out to describe the results of two unpublished studies on hosts’ recognition systems. The first study uses artificial colour manipulation of hosts’ own eggs to determine whether specific colours are perceived similarly to trigger rejection behaviours, irrespective of the presence of hosts’ own eggs in the nest. The results suggest that foreign egg colours are perceived similarly and rejection is triggered through comparisons with internal filters, or recognition templates, even when hosts’ own eggs are not present. The second study also uses artificial colour manipulation to assess the hosts’ specific behaviours to foreign eggs and reveals that relative patterns of egg ejection and nest desertion are indicative of hosts’ responses to foreign eggs. These results provide detailed new information for our understanding of parasitic birds’ impacts on hosts’ perceptual processes. It is also the aim of this thesis that these studies may also be used as starting points towards a sample set of methodological and analytical tools to determine whether and how other species, including people, may use similar perceptual, cognitive, and behavioural decision rules to detect foreign items in odd-egg-out paradigms.