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We explored characteristics and patterns of nest distribution, and their putative costs and benefits to breeding females, in polygynous Red-collared Widowbirds (Euplectes ardens). Red-collared Widowbirds differ from most other Euplectes species, in that male nest-building is reduced to simple nest-rings used in courtship; females alone position and build nests in the territories. Females used only 37% of available territory area for nesting and aggregated at the centers of territories, possibly to take advantage of male vigilance from prominent central perches or to avoid harassment by neighbors. However, irrespective of territory size or number of females on the territory, females maintained relatively even spacing, with nests ~15 m apart. Nest predation rates were higher (28.2% [day.sup.-1]) during the nestling period than during incubation (14.6%), but independent of the number of actively nesting females on a territory. During synchronous nestling stages, however, birds nesting close to other birds incurred higher predation costs. Females may, therefore, centrally clump their nests on a territory but maintain enough distance between nests to reduce nest predation. Females choosing unmated males (monogamous) received no greater costs or benefits than females settling with mated males (polygynous). Taken with our earlier finding of strong female preference for longer-tailed males (Pryke et al. 2001a), our results here suggest that females may gain indirect genetic benefits of higher-quality offspring without incurring the high costs of sharing territories. Received 20 August 2003, accepted 24 June 2004.

Research provides evidence for theories on why body size of the Speckled Mousebird has remained stable, rather than growing to overcome thermal limitations. Sufficient food availability, including a temporally dynamic dietary switch from leaves to fruit, enable Mousebirds to expend less energy in food gathering and more for thermal maintenance.

Fluctuating asymmetry (FA) may provide a direct test of whether sexual selection via 'arbitrary traits' or 'good genes' is responsible for the evolution of epigamic traits, because FA is an epigenetic measure of stress during development. However, tests of the FA hypothesis have yielded equivocal results, and the debate between arbitrary traits and good genes continues. The FA hypothesis predicts a negative relationship between ornament size and asymmetry. In non-ornamental traits, a U-shaped relationship between trait size and asymmetry is expected. We tested these predictions in the Red-collared Widowbird (Euplectes ardens) by examining the relationship between size and asymmetry in the length of the tail, tarsus, and wing. We found no significant linear or second-order polynomial relationships between trait size and asymmetry. Furthermore, no relationship existed between asymmetry and two indices of body condition. This suggests that the tail is not a reliable signal of male quality in the Red-collared Widowbird. However, we argue that the assumptions of the FA hypothesis are too simplistic for this conclusion to be drawn with a high degree of confidence.