Summary

Work on birds has prompted some key theoretical developments in the field of animal contests. Birds have an unusually conservative morphology, which constrains the ability of many species to fight physically, but many birds have evolved adaptations to aid in conflict resolution. These include the display of bright colours, elaborate vocalisations and physiological mechanisms. Birds also have a relatively conservative life history (parental care is ubiquitous), which influences the nature and extent of contests: for most birds, competition begins at birth for access to food provided by their carers. Intense resource competition continues into their adult lives, especially as many birds are territorial and/or reside in social flocks of related and/or unrelated conspecifics. At breeding, competition for access to mates is particularly severe, with birds competing both overtly and more cryptically to gain fertilisation precedence. Here I consider the diversity of avian contests.

Introduction

Bird contests can be highly conspicuous. An example is the ferocious fighting that occurs between two unfamiliar (or staged) jungle fowl (Gallus gallus domesticus) where males may fight to the death using sharp-pointed spurs as weapons (Mench 2009). Many avian contests are, however, less physical. Under more natural circumstances, for example within the jungle fowl's mixed-sex flock, disputes between flock members are unlikely to escalate to physical fighting (Ligon et al. 1990, Collias & Collias 1996). Agonistic encounters generally involve stereotyped behaviours, a range of complex vocalisations, and variation in conspicuously coloured morphological traits (e.g. Ligon et al. 1990, Cornwallis & Birkhead 2008). Nevertheless, the lack of physical contests does not necessarily indicate an absence of competition. Indeed, birds compete for the same things that cause and define competition in other taxa. However, there are a number of general avian morphological and life-history adaptations that are likely to have influenced the nature of competition in birds.