CLUTCH SIZE IN EASTERN PHOEBES (SAYORNIS-PHOEBE) .1. THE COST OF NEST-BUILDING

Eastern pheobes (Sayornis pheobe) may build new nests or repair previo usly built ones. New nests may be of two types: statant (built on supp orting ledges) or adherent (plastered to a vertical surface). Repaired nests are statant. Previous workers compared phoebes building new nes ts to those repairing old nests and found that adherent nests took mor e time and effort to build. Similarly, previous workers found that adh erent nests took more time and effort to build than statant nests. At the same time, these workers noted that smaller clutches were laid in new and adherent nests than in repaired and statant nests and conclude d that the reduction in clutch size was the result of building the for mer types of nest. This implies that an increase in the demands on par ental time and energy just before egg laying can decrease reproductive output proximally. However, the statistical support for this conclusi on was weak, and Dur reanalysis of the previously reported data does n ot support it. In addition, previous workers used the terms statant an d adherent inconsistently. We advise that nest types he carefully defi ned according to the expected effect of nest type on the bird's behavi our, not just according to the appearance of the nest. We found that b uilding new nests took longer than repairing old ones. However, we fai led to find a difference in the time required to build adherent and st atant nests. Furthermore, clutch size was apparently unrelated to the type of nest built. We found no relationship of clutch size to female age or clutch initiation date. The type of nest built for the first cl utch size of the season also was not related to the probability that t here would be a second clutch, the size of the second clutch, or the i nterval between clutches. More research is required to show conclusive ly that increased demands on time or energy just before egg laying can reduce the clutch size of small passerines.