Summers with Golden Swamp Warblers Aspects of the Breeding Biology of Prothonotary Warblers from 2018-2019 in Northeastern North Carolina Skadi Kylander
ABSTRACT
Every summer, southern swamps east of the Mississippi River host the only cavity-nesting species of warbler to breed in eastern North America. Prothonotary Warblers (Protonotaria citrea) rely on oldgrowth swamps in this area for breeding and to raise their young. Population declines in recent decades have sparked interest in understanding Prothonotary Warbler breeding biology. In 2018 and 2019, nest box occupancy, nest success, nestling growth rate, types of prey brought to nestlings, and standard measurements of adults were recorded in two eastern North Carolina habitats: the Chowan University Meherrin River Field Site (MRFS) with riparian and bottomland hardwood swamps, and a maritime forest containing depressional wetlands in the Kitty Hawk Woods Coastal Reserve (KHW). Six nest boxes were installed at each site for the 2018 breeding season. This was increased to 19 boxes at MRFS and 18 boxes at KHW for the 2019 season. Observations from the two breeding seasons yielded a total of 15 occupied nest boxes (11 at MRFS; 4 at KHW). While the percent of boxes occupied at MRFS (44%) appeared significantly higher (p = 0.04) than at KHW (17%), nest success at MRFS was significantly lower than at KHW (50% and 96% respectively, p = 0.0001). Likewise, comparison of mean nestling growth rates (MRFS = 0.9 g/ nestling/day; KHW = 1.2 g/nestling/day) approached significance (p = 0.06), with MRFS growth rates appearing lower. Preliminary analysis of nest provisioning suggests prey types and sizes differed between the two sites. Data was collected for a total of 14 adults between the two breeding seasons.
INTRODUCTION
Every summer, North America’s southern swamps east of the Mississippi River play host to the only cavity-nesting species of warbler to visit that part of the continent. These unique visitors are Prothonotary Warblers (Protonotaria citrea). Prothonotary Warblers are Nearctic-Neotropical songbirds (Petit, 1999) that winter in Central and South America (Tonra et al., 2019). They travel to North America for the duration of their breeding season, arriving in the spring and settling into old-growth swamps to breed and to raise their young. In recent decades, Prothonotary Warbler populations have declined, prompting their placement on several watch lists (Rosenberg et al., 2016; USFWS, 2008) and increasing interest in understanding their life cycles to develop better conservation efforts. Gaining an understanding of an organism’s full life cycle has been shown to aid in effective conservation (Marra et al., 2015). Though these birds spend a significant portion of the year in Central and South America (Tonra et al., 2019), northeastern North Carolina has been shown to contain one of the highest breeding densities of Prothonotary Warblers in North America (Petit, 1999), making it a promising area to use to study the breeding portion of their life cycle. A pilot study on Prothonotary Warblers nesting in northeastern North Carolina was started by Dr. Heather McGuire and Dr. James Dame from the Department of Biology at Chowan University in Murfreesboro, NC in 2018. As of 2019, the purpose of this study is to document and compare differences 18
