2023 Conservation Grant Recipients

“A 2-year project to better understand wood duck breeding success, brood habitat use, and chick survival in Maryland and Delaware. This research was born out of a multi year project spanning eight states across the Atlantic and Mississippi flyways to better understand wood duck nest site selection and recruitment. The goal is to understand how female wood ducks evaluate and choose a nest box. If we can understand this, then we can place more boxes in optimal conditions to increase their usage rates and produce more ducks. We are also using state of the art GPS and radio tracking transmitters attached to hens and ducklings to monitor their movements after they exit the nest box. GPS units record locations every hour which will allow us to analyze very finescale brood habitat usage as well as estimate current duckling survival rates. So far, we’ve collected data on over 780 nests and tagged 39 hen wood ducks and 117 ducklings. We will use this information to identify optimal brood rearing habitat conditions that provide necessary resources and protection to growing ducklings. We hope this will facilitate better habitat management practices and increase the availability of quality brood rearing habitat to boost survival rates of ducklings.”

Identifying Purple Martin diet and its effect on nestling development

Claire Bernard

“Purple Martins are obligate aerial insectivores, skillfully hunting their prey in the air. Like most birds during the breeding season, Purple Martin parents will bring the insects they catch back to the nest to feed their young. This project aims to quantify the diversity of insects martin nestlings are being fed and how the differences in diet may affect their growth and development. DNA metabarcoding will be used to identify insects in a nestling's diet by interpreting the genetic material found within a nestling's feces. We collected the fecal samples and measured nestling mass and tarsus length three times throughout their pre-fledge development. Fifteen total martin nests were sampled, located in Curtis Mill Park, Bucktoe Creek Preserve, and Longwood Gardens. Each colony's topography exhibits a range of differences such as its native plant abundance, foot traffic, and proximity to human development which all will affect insect diversity and abundance. Modeling the mass and tarsus length over time revealed that the Longwood Gardens nestlings weighed almost 50% less at their hatch date compared to their counterparts at Bucktoe and Curtis Mill. The nestlings from Longwood had noticeably lower mass and tarsus measurements than nestlings from the other two colonies, however this model was not statistically significant (p > 0.05). While mathematically insignificant, we should still operate under the assumption that there may still be biological factors at play that affect the nestlings' development. We are still evaluating the results of the DNA metabarcoding, but will update the Delaware Audubon Society with our analysis in the near future.”

“Caterpillars, particularly of moth species, are calorically and numerically valuable prey, especially for birds during the breeding season. They contribute nutrients that are an integral basis of diverse food webs and they are important pollinators (Macgregor et al., 2015). Caterpillar abundance, coupled with their high protein content, maintains avian, amphibian, mammalian, and reptile populations (Cooper, 1988; Ramsay & Houston, 2003; Wilson, 1987). North American caterpillars predominately feed on tree hosts, and subsurface pupation among arboreal Lepidoptera is widespread. Therefore, such species are vulnerable to the microhabitat conditions under host trees during the pupation stage. Current landscaping practices may be contributing to declines in Lepidopteran diversity and abundance, especially in compacted urban environments. Understory plant choice and detritus management following land development characterize subsurface soil conditions for overwintering pupae. My project seeks to determine how the influences of ground cover types on soil compaction, organic matter, and temperature variation impact survival and other measures of fitness in Manduca sexta (Sphingidae) and Anisota stigma (Saturniidae). Moth survival and fitness will be measured upon adult emergence in the summer of 2024. “Soft landings” are ground covers often recommended by conservationists as replacements for turfgrasses to increase the probability that insects will complete their life cycle (Holm 2022). This project investigates how soft landings might influence the overwintering survival of moth species. Our goal is to use this information to inform our landscaping recommendations and in turn, improve the ecological productivity of our urban spaces.”

“Nearctic-Neotropical migratory songbirds are experiencing dramatic population declines, primarily due to habitat loss. Sea level rise (SLR) is a significant cause of coastal habitat loss, especially along the Delaware Bayshore, where rates of SLR are approximately twice the global average rate. While the use of Delaware Bay near-shore habitats by migratory shorebirds and waterfowl is well-documented, much less is known about the use of these habitats by migratory songbirds. The goal of our project was to quantify the importance of these Delaware Bay habitats to songbirds during the fall migration season. For our project, birds were captured using mist-nets at Milford Neck Conservation Area from September 6th to November 3rd, 2023. Each individual capture received an individually-numbered USGS leg-band, and morphometric measurements were taken. In total, we had over 1000 captures from 50 different species, including Gray Catbirds, Common Yellowthroats, American Redstarts, and Veeries. Our most common species was the Yellow-rumped Warbler – we caught almost 450 of them! Adjusted for effort, the total number of captures was comparable to total captures elsewhere along the Atlantic Coast, thus confirming the global conservation importance of the Delaware Bay Coast to migratory songbirds for the first time. Hopefully, the results of this study, combined with existing data from research on SLR in Delaware Bay, can be used to identify and prioritize focal areas and coastal habitats for conservation, management, and restoration.”

The Hawk Migration Association of North America has an online database for count data at over 300 North American hawkwatch sites over the last few decades (www.hawkcount.org). Using the information gathered by the Cape Henlopen (2011-2021) and Ashland Nature Center (2017-2023) hawk watches in DE, and the Cape May (2008-2020) hawk watch in NJ, my goal was to model temporal and environmental factors that influence the hourly passage rates of raptors during fall migration. I also used weather radar observations from the KDOX radar in Dover, DE to test for correlation between hourly observations of migrating raptors with the radar reflectivity measures of bird biomass. Passage rates of raptors were generally greater with slow tailwinds, winds from the North, higher air pressure, no precipitation, and lower total cloud cover. Species that showed the steepest relative population declines since 2008 include Peregrine Falcon (-53%), Black Vulture (-50%), and Sharp-shinned Hawk (-25%). Species with the greatest relative population increases since 2008 include Broad-winged Hawk (+1275%), Turkey Vulture (+90%), Osprey (+82%), Red-Shouldered Hawk (+62%), and American Kestrel (+50%). However, some of these trends may be influenced by differences in the sites used for certain years. Site specific trends are still being analyzed. The relationship between radar reflectivity and visually detected raptors was weakly positive.