The influence of male territorial and foraging behaviours on female choice has received little attention in studies of resource-defence mating systems even though such male behaviours are thought to affect variation in their territory quality and mating success. Here we show that female purple-throated carib hummingbirds preferred to mate with males that had high standing crops of nectar on their flower territories. A male's ability to maintain high nectar standing crops on his territory not only depended on the number of flowers in his territory, but also on his ability to enhance his territory through the prevention of nectar losses to intruders. We observed that males defended nectar supplies that were two to five times greater than their daily energy needs and consistently partitioned their territories in order to provide some resources to attract intruding females as potential mates. Such territorial behaviour resulted in males defending some flowers for their own food and other flowers as food for intruding females. Collectively, our results suggest that variation in mating success among males is driven primarily by variation in territory quality, which ultimately depends on a male's fighting ability and size.
