Avian Conservation and Ecology (Jun 2022)
Land cover habitat associations of breeding marsh birds and priority waterfowl differ in eastern Canada
Abstract
Waterfowl (ducks, geese, swans) are among the few bird groups showing recent population increases in North America. By contrast, marsh birds (bitterns, rails, grebes) are declining, despite this group appearing to benefit from many of the same conservation actions applied for waterfowl. To help understand this dichotomy, we 1) assessed land cover habitat associations for breeding marsh birds and priority waterfowl in eastern Canada at a broad range of spatial scales, and 2) compared these results between guilds - using data collected by the Maritimes Marsh Monitoring Program of Birds Canada. As we observed variation both within and between these groups, managers will do well to take species-specific or life-history-based approaches to wetland conservation and landscape management. Nonetheless, we offer guild-level generalizations that capture the majority of the effects on occupancy for the species we analyzed in our study area. We found that occupancy of both groups was higher in protected wetlands (e.g., in parks, land trusts) and at wetlands influenced by water control structures; however, marsh birds may benefit more than waterfowl from water level control. Occupancy by both groups increased with increasing amounts of water and wetland in the surrounding landscape, but this was more pronounced and included a greater variety of wetland types at broader spatial scales for marsh birds compared to waterfowl. Some marsh birds showed negative associations with urban land use and none had strong relationships with agriculture, yet occupancy of nearly all waterfowl increased with either urban or agricultural land cover. Actions that will benefit both groups include conserving large wetland complexes interspersed with, and surrounded by, low and intermediate amounts of urban and agricultural land use, respectively. A greater understanding of habitat use by wetland bird species helps construct sustainable working landscapes that benefit both birds and people.
