Effects of local and landscape-scale habitat variables on abundance and reproductive success of wetland birds

Abstract

Both local and landscape-scale habitat variables influence the abundance of wetland breeding birds. Few studies, however, simultaneously assess the effects of habitat variables at multiple spatial scales or consider effects on reproductive success. Therefore, we examined the effects of wetland and landscape-scale habitat variables on the abundance of nine breeding bird species and the effects of nest, wetland, or landscape-scale habitat variables on the nest success, clutch size, or number of fledglings of four species at 15 cattail (Typha sp.)-dominated wetlands in an agricultural region around Peterborough, Ontario, Canada. The abundance of Least Bittern (Ixobrychus exilis), Common Moorhen (Gallinula chloropus), and Marsh Wren (Cistothorus palustris) increased as wetland water depth increased; the abundance of Common Moorhen and Marsh Wren increased as wetland size increased; and the abundance of Marsh Wren increased as the amount of wetland in the surrounding landscape increased. Red-winged Blackbird (Agelaius phoeniceus) nest success decreased as nest cover increased. Clutch sizes were uninfluenced by the habitat variables that we considered. The number of Red-winged Blackbird fledglings per successful nest increased as wetland size increased and as the amount of wetland in the surrounding landscape increased. We speculate that food limitation in small wetlands may be responsible for the pattern in Redwinged Blackbird fledging success. The abundance and nest success of Virginia Rail (Rallus limicola) and Sora (Porzana carolina) were uninfluenced by the habitat variables we considered. Future research should consider mate attraction and productivity in relation to local and landscape-scale habitat variables for these and other secretive species. Our study suggests that wetland conservation will be most effective if it considers habitat variables at multiple spatial scales.

The accuracy of land cover-based wetland assessments is influenced by landscape extent

“…The idea that the optimal landscape extent for assessing biotic integrity might be speciesspecific is supported by other bird studies. For example, Tozer et al (2010) found that both Marsh Wren and Least Bittern abundances were related to the proportion of wetland in the surrounding landscape, but at different spatial extents. They suggest that the positive relationship between wetland habitat and bird abundance is due to a greater influx of dispersing individuals in landscapes with a greater proportion of wetland habitat, although such a mechanism would apply equally to plants through the dispersal of their propagules, either by wind, water, or animal vectors.…”

Migrating and breeding bird use of restored shallow lakes in Iowa

“…The positive relationship between Typha sp. and counts of breeding marsh birds has been found by other studies and in other regions of North America (Tozer et al 2010, Lupien et al 2014. In particular, the robust leaves of Typha sp.…”

“…Thus, larger wetlands may provide a greater variety of food items that can accommodate more individuals and species Dinsmore 1986, Brown and. Additionally, several SMBs such as the Least Bittern, Pied-billed Grebe, and American Coot prefer larger wetlands, but this may be due to greater water depths and emergent vegetation cover (Tozer et al 2010, Baschuk et al 2012, Monfils et al 2014). …”

“…Robust emergent vegetation can provide appropriate habitat conditions for several species of secretive marsh birds , Tozer et al 2010. Several species will build their nests at the base of emergent vegetation and may use the leaves as a canopy (Weller 1961, Conway 1995.…”

“…Specifically, we made several hypotheses concerning the effect of vegetation variables on two groups and three species of birds. Marsh passerines included four species of obligate wetland breeding passerines We assessed these groups because they require emergent vegetation for nesting and foraging , Tozer et al 2010.…”