BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

The Columbia Wetlands are one of the largest contiguous wetland complexes in western North America. Current population estimates are necessary for designation of priority conservation areas and for reliable assessment of population status for species of conservation concern. This multi-year study (2016-2019) was designed to estimate abundances of focal and secondary marsh birds using standardized call-broadcast protocols and distance sampling methods. Abundances of focal species varied by year, and mean population estimates indicated the most abundant secretive marsh birds were Sora (Porzana carolina; 4605 birds), followed by American Coot (Fulica americana; 2358 birds), Virginia Rail (Rallus limicola; 2124 birds), and Pied-billed Grebe (Podilymbus podiceps; 1657 birds). Most abundant secondary species were Marsh Wren (Cistothorus palustris; 6328 birds), Red-winged Blackbird (Agelaius phoeniceus; 5422 birds), Yellow-headed Blackbird (Xanthocephalus xanthocephalus; 884 birds), and Wilson's Snipe (Gallinago delicata; 445 birds). Habitat covariates for detection functions varied by species, tended to include woody vegetation, tall vegetation, and open water; supporting previous studies proposing that a 'hemi-marsh' state is an important habitat condition for many marsh bird species. The Columbia Wetlands provide important wetland habitat and these estimates underscore the need for effective management for the conservation of British Columbia's avifauna.

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Dam construction projects have created opportunities for water security, targeted flood protection, and energy production but at the cost of increasing anthropogenic pressure on affected aquatic ecosystems. Wetland ecosystems are often among the most vulnerable, as underlying hydrological regimes influence overall wetland structure and function. Marsh bird species are wetland and riparian habitat specialists, many of which are experiencing population declines across North America. We examined how the alteration of hydrological regimes for generating hydroelectric power affected the occurrence of secretive marsh bird species in the western montane region of British Columbia, Canada. We established survey stations in wetlands across 2 regions, the West Kootenay and the Columbia Wetlands, sampling across a spectrum of hydrological regimes and other potentially relevant factors. At each station, we assessed wetland occupancy during the breeding season using broadcast‐callback surveys focused on 5 secretive marsh bird species: American bittern (Botaurus lentiginosus), American coot (Fulica americana), pied‐billed grebe (Podilymbus podiceps), sora (Porzana carolina), and Virginia rail (Rallus limicola). Additionally, we measured vegetation structure and the proximity and size of nearby water bodies for each survey station. We then used occupancy models to assess important correlates behind wetland occupancy for these marsh bird species, considering water management operations, regional differences, and local‐ and landscape‐level wetland characteristics. Secretive marsh bird species were more likely to occupy wetlands in areas with less frequently altered hydrological regimes. Occupancy models highlighted local‐ and landscape‐level characteristics as important correlates for wetland occupancy by marsh birds. Wetlands with frequently altered hydrological regimes had more open water cover and less tall vegetation present, conditions that were negatively associated with occupancy. Altered wetlands in this study were farther from the next nearest wetland, which was also negatively associated with occupancy. We suggest reservoir management is altering vegetation communities within these wetlands, indirectly promoting lower occupancy of secretive marsh bird species.