Timing and duration of egg laying in duettingBuff-breasted Wrens

Using direct observations of Buff-breasted Wrens (Thryothorus leucotis), I examined timing andduration of egg laying, the behavior of females and males around the time of laying, and duetting and solo singingon laying and non-laying mornings. When laying, females roosted either alone in breeding nests or with their matesin dormitory nests, and left them on average 3.5 min before sunrise. Females returned to their nests at 18.6 minafter sunrise and took 21.1 min to lay their eggs. Almost all females were accompanied by their mates to the nestbefore laying, most males foraged near the nest during laying, and nearly all pairs re-united shortly after laying.Pairs sang significantly fewer duets and females gave significantly fewer solo songs on laying versus non-layingmornings, while males did not change their solo singing behavior. Singing was not restricted to times when femaleswere off their nests, as some pairs duetted and some males gave solo songs while females were laying. These resultssuggest that females lay their eggs at a time of day which is unfavorable in terms of duetting, and, in turn, fordefence of mates and territories.

Sharon A. Gill, J. Field Ornithol. 74(1):31-36, 2003