Female cuckoo calls misdirect host defences towards the wrong enemy.

Prey are sensitive to even subtle cues of predation risk, which provides the evolutionary potential for parasites to exploit host risk perception. Brood parasitic common cuckoos (Cuculus canorus) lay their eggs in the nests of host species and their secretive laying behaviour enables them to evade host defences. Therefore, it seems paradoxical that female cuckoos often give a conspicuous 'chuckle' call after parasitizing a host's clutch.

Sexually selected sentinels? Evidence of a role for intrasexual competition in sentinel behavior.

Although the evolutionary mechanisms that favor investment in cooperative behaviors have long been a focus of research, comparatively few studies have considered the role that sexual selection may play. For example, evolutionary explanations for sentinel behavior (where 1 individual assumes an elevated position and scans the surroundings while other group members forage nearby) have traditionally focused on the inclusive fitness benefits arising from its effects on predation risk, while its potential role in defense against intrasexual competitors remains largely unexplored. Here, we provide experimental evidence of a role for sentinel behavior in intrasexual competition, in a cooperatively breeding songbird, the white-browed sparrow weaver ().

Dominance-related seasonal song production is unrelated to circulating testosterone in a subtropical songbird.

Circulating testosterone (T) is widely considered to play a key role in the production of sexual displays by male vertebrates. While numerous studies support a role for circulating T in promoting the production of song in male birds, this understanding is based primarily on evidence from seasonally breeding northern temperate species, leaving it unclear whether this mechanism generalizes to other regions of the world. Here we investigate whether variation in circulating levels of T can explain the marked within- and among-individual variation in male song performance observed in a subtropical population of the year-round territorial white-browed sparrow weaver (Plocepasser mahali mahali).

Dominant male song performance reflects current immune state in a cooperatively breeding songbird.

Conspicuous displays are thought to have evolved as signals of individual "quality", though precisely what they encode remains a focus of debate. While high quality signals may be produced by high quality individuals due to "good genes" or favourable early-life conditions, whether current immune state also impacts signalling performance remains poorly understood, particularly in social species. Here, we experimentally demonstrate that male song performance is impaired by immune system activation in the cooperatively breeding white-browed sparrow weaver (Plocepasser mahali).