Small wetlands embedded in row-crop agriculture provide important brood-rearing habitat for dabbling ducks

The Prairie Pothole Region supports over half of North America’s breeding dabbling ducks and is globally recognized as a priority landscape for wetland and grassland conservation. However, widespread agricultural expansion has resulted in extensive conversion of habitat to row-crops, and wetlands ≤10 ha and embedded in row-crops are at high risk of loss or degradation. Wetlands surrounded by row-crops are further subjected to altered hydrology and runoff of sediment and chemicals, which may degrade plant communities and aquatic invertebrates that serve as key food resources for breeding ducks and their offspring. In this study, we used uncrewed aerial vehicles equipped with thermal and visual imaging cameras to quantify duck brood abundance and assess how wetland characteristics influence brood abundance across row-crop dominated landscapes of North Dakota, South Dakota, Minnesota, and Iowa. During the summers of 2019–2020, we surveyed 230 wetlands and detected 305 dabbling duck broods. Using N-mixture models, we estimated a mean detection probability of 0.56 (95% CI: 0.46–0.65) that was primarily influenced by observers, with little effect of time of day, weather, or vegetation characteristics. Brood abundance averaged 1.08 broods/wetland (95% CI: 0.89–1.44), increased with the natural log of wet area (β = 0.80; 95% CI: 0.52–1.10), and the natural log of aquatic invertebrate abundance (β = 0.19; 95% CI: 0.00–0.39), and decreased with wetland depth (β = –0.24; 95% CI: –0.48 to 0.00). Although brood abundance increased with wet area, brood density declined with increasing wet area, suggesting that conserving multiple small wetlands may support more broods than a single large wetland of equivalent total area. Our results demonstrate that wetlands embedded in row-crops provide important brood-rearing habitat and highlight the value of conserving small wetlands within highly altered agricultural landscapes of the United States Prairie Pothole Region.