Clearing up the court: sex and the endocrine basis of display-court manipulation

- The display environment can influence female perception of male courtship signals.
- Male golden-collared manakins display at courts they maintain clear of debris.
- Court cleaning is activated by testosterone in males but not in females.
- Highly motivated males clear heavy debris by flying away with it in their bill.
- Female assessment of male display drives male performance of cleaning behaviour.

Sexual selection can drive the evolution of novel traits, including behaviours, that may arise in sex-specific patterns and be under sex-steroid hormone control. In some polygynous species, males actively manipulate their display environment, likely to influence female perception of male sexual traits. As a presumptive appetitive reproductive behaviour, the motivation to manipulate the display environment may be activated by reproductive hormones and the degree of motivation may vary across individuals. To evaluate these possibilities, we examined the hormone dependence of court-clearing behaviour in lek-breeding golden-collared manakins, Manacus vitellinus, of Panama where males clean the rainforest floor of debris within display courts and maintain these cleaned courts during the long breeding season and during subsequent years. Nonbreeding females and juvenile males were given implants containing testosterone (T) or empty (control) implants and observed in a large aviary situated in the middle of Panamanian rainforest. The aviary was planted with saplings around which males display; the bare ground was covered with dried leaves. Control-treated males removed only a few leaves from their courts. T treatment dramatically stimulated court-cleaning behaviour, including both the removal of leaves and attempts to extract small seedlings from the soil. None of the females displayed court-cleaning behaviour, although T-treated females showed low levels of some male courtship displays as well as significant levels of aggressive behaviour. To assess wild adult males' motivation to clear courts, we presented lekking males with weighted artificial leaves. Males were attentive to the leaves and motivated to remove them. With increasing weight, males utilized different methods, which often involved multiple repeated attempts to move leaves. These findings demonstrate that manakins exhibit sex-specific and hormone-dependent court-cleaning behaviours and that males are highly motivated and physically adapted to keep their courts clean.