Relationships between body composition, body size and alternative reproductive tactics in a lekking sandpiper, the Ruff (Philomachus pugnax)

1. The Ruff is a lekking sandpiper in which males have two genetically determined alternative mating strategies: 'satellite' or 'independent'. Satellite males are nonterritorial, following groups of females on and off leks. Independent males attempt to establish territories on leks and can be either 'resident' territory holders, or nonterritorial 'marginals'. The time budgets of the three behavioural tactics (resident, marginal and satellite) differ notably in time allocated to foraging, aggression and display activity. These differences have led to the suggestion that the benefits of size and energy stores may vary with mating tactic. 2. In this paper in vivo estimates of body composition (fat, fat-free mass) for breeding male Ruffs using total body electrical conductivity (TOBEC) are presented. 3. Satellite males have significantly shorter tarsi and wings than independent males. 4. After correcting for size, independent males are significantly heavier and fatter than satellites, and marginals in particular are heavier and fatter than both residents and satellites. 5. Estimates of energy expenditure during flight suggest that satellites may maintain reduced energy reserves to minimize flight costs, while the larger fat stores of independent males are consistent with the benefits of endurance as a territory holder.