DIRECT REMOVAL OF FECAL SACS BY ROCK WRENS

摘要

Removal of fecal sacs from nests during nestlings' development is an adaptive behavior shared by most species of passerines (Skutch 1976, Welty 1982,Weather- head 1984). The selective forces that have shaped nest-sanitation behavior remain unclear, but clean nests are thought to be less likely to attract predators (Petit and Petit 1987, Petit et al. 1989; but see Ibá?ez-álamo et al. 2014a）. Nest-sanitation behavior also appears to improve a host's rejection of a brood parasite's eggs (Moskat et al. 2003, Guigueno and Sealy 2012). In many studies nest sanitation is linked explicitly to measures of parental investment, including feeding rates (Ricklefs 1977, Gustafsson and Sutherland 1988, Markman et al. 2002). All of these studies indicate that the removal of fecal sacs can improve reproductive success for the parents, but fewer studies have focused on the role of nestlings' behavior in nest sanitation, particularly in coordination with parental actions. Such behaviors have been known for some time. For example, Blair and Tucker (1941) described "active cooperation" behaviors, in which nestlings of multiple species with varied nest types were observed making deliberate movements to facilitate removal of their feces. Selection for behaviors that facilitate efficient removal of fecal material should be beneficial because they prevent nest contamination and decrease the time and energy expenditure given to nest sanitation （Thomson 1935, Spencer 2005,Ibá?ez-álamo et al. 2013）. Nestlings of a few passerine species have been observed to raise their tails in response to adults' visits to the nest in order to facilitate cloacal stimulation, after which the adults pick up the fecal sacs and either remove them from the nest or eat them (Selous 1933,Smith 1942, Davis 1978). Other researchers describe parent birds waiting near nestlings to remove fecal sacs from the nest floor (Gabrielson 1912, Laskey 1948, Ley and Williams 1998). In the House Wren (Troglodytes aedon) in Surinam, Haverschmidt (1952) described parents removing fecal sacs directly from the cloacae of nestlings, a behavior also described by Dobbs et al. (2001) in the Scaled Antpitta (Grallaria guatimalensis). This direct removal of fecal sacs likely eliminates a parent bird's need to search for and pick up feces during the time of maximum provisioning effort, and it could limit the amount of potentially harmful bacteria within nests （Ibá?ez-álamo et al. 2014b). Direct removal of fecal sacs can be difficult to observe, particularly in cavity nests or nest boxes, and may therefore go underreported and undescribed. To date there have been few accounts of nestlings cooperating with parents to remove waste in species nesting in rock cavities, and even fewer photos or videos documenting such coordinated sanitation behaviors.