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 dete rmined alternative mating strategies: 'satellite' or 'independent'. Satelli te males are nonterritorial, following groups of females on and off leks. I ndependent males attempt to establish territories on leks and can be either 'resident' territory holders, or nonterritorial 'marginals'. The time budg ets of the three behavioural tactics (resident, marginal and satellite) dif fer 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) a re presented. 3. Satellite males have significantly shorter tarsi and wings than independ ent males. 4. After correcting for size, independent males are significantly heavier a nd fatter than satellites, and marginals in particular are heavier and fatt er than both residents and satellites. 5. Estimates of energy expenditure during flight suggest that satellites ma y maintain reduced energy reserves to minimize flight costs, while the larg er fat stores of independent males are consistent with the benefits of endu rance as a territory holder.