Decline of the Dusky Canada Goose (Branta canadensis occidentalis; hereafter, Dusky Goose) population on the western Copper River Delta (CRD) prompted the establishment of an artificial nest island (island) program in 1983. A retrospective analysis of the program was conducted to examine general trends in island use and nest success from 1984–2005. A series of candidate models was generated to determine how habitat, island and biological variables were associated with island use and nest success from 1996–2005. Use of islands by Dusky Geese increased between 1987 and 2005 from 10% to 44%; apparent nest success averaged 64 ± 4% and showed no trend with year. Island use was consistently and strongly associated with the previous year's island status. The odds of nesting on an island that contained a successful nest the previous year were four times greater than for islands not used the previous year. Likelihood of island use was highest at moderate shrub cover and increased with shrub height. Likelihood of nest success increased on islands further from shore. The influence of year suggests the presence of alternate prey and predator abundance is more important to nest success than island features. The increasing use of islands while the CRD Dusky Goose population has been declining indicates that islands may be increasingly important to population productivity. However, quantifying the contribution of the island program requires a better understanding of other population metrics, such as gosling mortality.
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Vol. 34 • No. 3