Changes in Loon (Gavia spp.) and Red-necked Grebe (Podiceps grisegena) Populations in the Lower Matanuska-Susitna Valley, Alaska

Résumé

More than two-thirds of the human population of Alaska resides in the south-central portion of the state, where its continued growth is likely to affect some wildlife populations negatively. To assess changes in waterbird populations in this region, we compared counts of Common Loons (Gavia immer), Pacific Loons (G. pacifica), and Red-necked Grebes (Podiceps grisegena) made on Matanuska-Susitina Valley lakes. In general, the number of lakes occupied by loon or grebe pairs decreased between 1987 and 1999. Decreases in the number of lakes occupied by Common Loons were less drastic in the northwest region of the study area than in the southeast region; human development is greater in the southeastern portion of our study area. Contrary to lake occupancy, the percentage of lakes that fledged Common Loon chicks remained stable between years. Because the human population is expected to continue to grow, proactive management of lake use and lakeshore development, coupled with monitoring of loon and grebe occupancy and productivity, is needed to ensure the persistence of these waterbird populations in the lower Matanuska-Susitna Valley.