Density, Abundance, and Habitat Associations of the Inland Swamp Sparrow (Melospiza georgiana georgiana) in Iowa

Abstract

Wetlands continue to decline throughout North America and the Prairie Pothole Region, thus emphasizing the importance of understanding population trends and habitat associations of wetland species to ensure effective conservation and habitat management of those species. We estimated density and abundance and evaluated habitat associations of the Inland Swamp Sparrow (Melospiza georgiana georgiana) in Iowa. We conducted standardized distance sampling surveys for Swamp Sparrows and measured habitat characteristics at 307 wetlands in two regions of Iowa in 2009 and 2010. We used Program Distance to model detection probability and estimate region-specific breeding densities of Swamp Sparrows at Iowa wetlands. We then extrapolated density estimates to the total area of wetlands in each region to obtain estimates of breeding abundance. We correlated Swamp Sparrow counts to nine habitat variables using Poisson regression in Program R. Swamp Sparrow counts were positively correlated with percent cover of cattail (Typha spp.) and water depth (cm) and negatively correlated with percent cover of woody vegetation, vegetation size (m), and wetland size (ha). We estimated breeding densities of Swamp Sparrows to be 1.488 birds/ha (95% CI = 1.308 − 1.692) in region 1 (Des Moines Lobe landform) and 0.041 birds/ha (95% CI = 0.006 − 0.275) in region 2 (remainder of the state). Our results, in comparison to those of other studies, indicate that Swamp Sparrows associate with a variety of wetland characteristics depending upon what is available. Swamp Sparrows are relatively uncommon breeders in Iowa, and our work confirms that most occur in the Des Moines Lobe landform in north-central and northwestern Iowa. Biologists and land managers should incorporate our findings on this species' habitat associations into management activities to ensure that Swamp Sparrow populations persist into the future. ABSTRACT.-Wetlands continue to decline throughout North America and the Prairie Pothole Region, thus emphasizing the importance of understanding population trends and habitat associations of wetland species to ensure effective conservation and habitat management of those species. We estimated density and abundance and evaluated habitat associations of the Inland Swamp Sparrow (Melospiza georgiana georgiana) in Iowa. We conducted standardized distance sampling surveys for Swamp Sparrows and measured habitat characteristics at 307 wetlands in two regions of Iowa in 2009 and 2010. We used Program Distance to model detection probability and estimate region-specific breeding densities of Swamp Sparrows at Iowa wetlands. We then extrapolated density estimates to the total area of wetlands in each region to obtain estimates of breeding abundance. We correlated Swamp Sparrow counts to nine habitat variables using Poisson regression in Program R. Swamp Sparrow counts were positively correlated with percent cover of cattail (Typha spp.) and water depth (cm) and negatively correlated with percent cover of woody vegetation, vegetation size (m)...

Wetland Characteristics and Wintering Passerellidae Occupancy on Agricultural Conservation Easement Program Wetlands in West Virginia

“…Song sparrows were more likely to occur at sites with less bare ground and dark-eyed juncos were more likely to occur at sites with at least some shrubs at the 5x5 m scale which could be an indication that Passerellidae sparrows select wintering habitat with denser herbaceous and shrub screening cover. The absence of any significant association between swamp sparrow occupancy and dense vegetation is contrary to what has been found previously (Harms and Dinsmore 2015). This may be because swamp sparrows select habitat with dense vegetation at a different scale than what we measured, or select wintering habitat based on other habitat-scale characteristics.…”

“…Reference wetlands were typically located within a contiguous forested or wetland landscape which may have excluded some wintering Passerellidae species that require a certain amount of open-field habitat, edge, or habitat diversity. Similarly, swamp sparrows were more likely to be found on ACEP wetlands and are often associated with native emergent vegetation (Harms and Dinsmore 2015). While emergent vegetation was prevalent on both ACEP and reference sites, invasive herbaceous material was higher on reference sites (Lewis, Chapter 1).…”

“…Consistent with other studies, we found evidence that screening cover is an important component of wintering avian habitat. Even small areas of herbaceous buffers can promote avian presence through all seasons (Baldwin et al 2007, Blank et al 2011, Harms and Dinsmore 2015, Marcus et al 2000. Dense herbaceous or shrubby cover provides hiding and foraging habitat, and also acts as thermal cover in the winter (Carr and Lima 2014).…”

Detection and density of breeding marsh birds in Iowa wetlands

“…Previous work has examined the detection probability of marsh birds and how several factors influence detection of different species [23,50,52,66], and our study further highlights variables that should be considered when surveying for breeding marsh birds. Of particular concern is the experience of observers [87,88].…”

“…In Iowa, published studies have estimated the detection probability and density of several marsh bird species across the state [50][51][52], but none have attempted to obtain estimates particular to restored and pre-restored wetlands. The Shallow Lakes Restoration Project (SLRP) is focused on restoring shallow lakes throughout the Iowa PPR in order to improve conditions for wildlife.…”