Effects of gull predation and weather on survival of emperor goose goslings

Numbers of emperor geese (Chen canagica) have remained depressed since the mid-1980s. Despite increases in glaucous gulls (Larus hyperboreus), a prima ry predator of goslings, little information existed to assess whether recen t patterns of gosling survival have been a major factor affecting populatio n dynamics. We used observations of known Families of emperor geese to esti mate rates of gosling survival during 1993-96 on the Yukon-Kuskokwim Delta. Alaska. Survival of goslings to 30 days of age varied among years from 0.3 32 during 1994 to 0.708 during 1995. Survival was lowest during 1993-94, wh ich corresponded with the years of highest frequency of disturbance of goos e broods by glaucous gulls. Rainfall during early brood rearing was much hi gher in 1994 than other years. and this corresponded to low survival among goslings less than or equal to5 days of age. Numbers of juveniles in famili es during fall staging were negatively related to rainfall during early bro od rearing (n = 23 yr). Although there are no data to assess whether goslin g survival in emperor geese has declined from some previous level, current survival rates of emperor goose goslings are as high as or higher than thos e observed in other goose species that are rapidly increasing. A proposed r eduction of glaucous gull numbers by managers may not be the most effective means for increasing population growth in emperor geese.