Temperature and Predation Effects on Abundance and Distribution of Lesser Snow Geese in the Sagavanirktok River Delta, Alaska

Abstract

The largest and most productive colony of Snow Geese (Chen caerulescens caerulescens) in Alaska for two decades (1980-1999) was on Howe Island in the outer Sagavanirktok River Delta. Petroleum development began in this area during the mid-1980s, and studies of Snow Geese on Howe Island were conducted annually since 1980. Annual gosling production remained high and the colony expanded during 1980-1993; thereafter both gosling production and colony size declined. During 1980-1993, gosling production was highly and positively correlated with mean daily air temperature during the 1-25 June incubation period, and predation at the colony was insignificant. After 1993, there was an increase in predation on Snow Goose eggs at Howe Island by Grizzly Bears (Ursus arctos) and other mammalian and avian predators, which resulted in the decline of the Howe Island colony. New Snow Goose colonies east of the oil fields expanded during the decline on Howe Island. Evidence suggests that this eastward expansion likely resulted from dispersal or displacement of geese from Howe Island. After 1993, the effects of predation confounded the known effects of spring temperatures, and predation became the significant factor influencing gosling production. Increased predators in the Prudhoe Bay area and at Howe Island were suspected to be linked to the availability of human food waste and refuse and to the cessation of hunting and trapping in the area. Recently imposed mitigation measures have included better refuse and waste management and removal of problem bears. These measures should result in reduced predation and increased productivity at the Howe Island Snow Goose colony.