North American Crane Working Group
Proceedings of the North American Crane Workshop
Date of this Version
2023
Document Type
Article
Citation
Proceedings of the North American Crane Workshop (2023) 16: 35–43
Abstract
Pacific coast Canadian sandhill cranes (Grus canadensis rowani) breed in coastal regions of British Columbia and southeast Alaska and are considered a unique population within the Pacific Flyway. These cranes stage during fall migration along the Lower Columbia River at Sauvie Island Wildlife Area (SIWA), Oregon, Ridgefield National Wildlife Refuge (RNWR), Washington, and on adjacent lands. Peak numbers of cranes congregate here in late September through mid-October, with most of these cranes continuing south to winter in the Central Valley of California. During 2003–2024, we conducted single-day counts annually of cranes during peak fall migration as cranes flew into their evening roosts at SIWA, RNWR, and adjacent lands. We also conducted age-ratio counts at 1 of the primary roost sites on SIWA. Population counts indicated a significant upward trend (Y = 81.35X + 3425; r2 = 0.45; P < 0.001) from 2003 to 2024, with peak annual counts of over 5,000 individuals in 5 of the past 8 years. The mean annual age ratio (% young in the roost) was 9.4% (SE = 0.4, n = 22, 95% C.I. = 8.7–10.2). Together, the population counts and age ratio counts indicate a stable to increasing population for this group of cranes that migrate through the Lower Columbia River in Oregon and Washington. The roost sites are on the public wildlife areas and are protected from threats of development; however, drought or other impacts to the hydrology of the area could threaten roosting habitat. Additionally, these cranes regularly forage on adjacent private agricultural fields; changes in crop plantings or land-use patterns from urban development would reduce the availability of this important foraging habitat for these cranes during fall stopover in this area.
Comments
United States government work