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.Les associations d'habitats de couverture terrestre des oiseaux de marais nicheurs et de la sauvagine prioritaire diffèrent dans l'est du Canada RÉSUMÉ. Les oiseaux aquatiques (canards, oies, cygnes) fait partie des quelques groupes d'oiseaux dont la population a récemment augmenté en Amérique du Nord. En revanche, les oiseaux des marais (butors, râles, grèbes) sont en déclin, bien que ce groupe semble bénéficier d'un grand nombre des mêmes mesures de conservation que celles appliquées aux oiseaux aquatiques. Pour mieux comprendre cette dichotomie, nous avons 1) évalué les associations d'habitats de couverture terrestre pour les oiseaux de marais nicheurs et les oiseaux aquatiques prioritaires dans l'est du Canada à une large gamme d'échelles spatiales, et 2) comparé ces résultats entre les guildes -en utilisant les données recueillies par le Programme de surveillance des marais des Maritimes d'Oiseaux Canada. Comme nous avons observé des variations tant au sein de ces groupes qu'entre eux, les gestionnaires auront intérêt à adopter des actions de la conservation ...

Wetland management practices and secretive marsh bird habitat in the Mississippi Flyway: a review

“…There is some evidence that waterfowl act as umbrella species for SMBs; Bradshaw et al (2020) reported that on public wetlands in Illinois, USA, SMB occupancy peaked at wetlands with intermediate levels of waterfowl management intensity. Yet other researchers reported waterfowl and SMBs have significantly different habitat associations (Valente et al 2011, Studholme et al 2022. Despite the dearth of information and contradictory outcomes from past researchers, concerns over SMB declines have prompted interest in SMB-focused management at some public wetlands.…”