Influence of patch shape on mallard nest survival in northern Iowa

Abstract

Reproductive success of mallards (Anas platyrhynchos) is influenced by distribution and amount of wetlands and grasslands on the landscape during the breeding season. Most studies of mallard reproductive success have been conducted in areas with high wetland densities and large tracts of grasslands. We investigated nest survival of mallards in intensively cropped northern Iowa, USA, where wetland and grassland habitats were highly fragmented. We radiotracked female mallards nesting during 1998-2000 and located 318 nests in 6 types of land cover. Overall daily survival rate of nests was 0.945 AE 0.003 standard error (SE), corresponding to an estimated nest survival rate of 0.14. Hen success (i.e., the probability that an individual female will hatch a nest in one of her attempts) averaged 0.28 AE 0.03 SE. We used a model selection approach to examine covariates that might affect nest survival. Perimeter-to-area ratio (PAR) of the nest patch was the most important predictor of daily nest survival, with nest survival decreasing with increasing PAR. A greater percentage of nests hatched (18%) in habitats with low perimeter-to-area ratios (e.g., pastures, hayfields, Conservation Reserve Program fields, and managed grasslands) compared with habitats with high PAR (11%) such as drainage ditches, road-side ditches, fencerows, and waterways. Managing habitat in this region to increase mallard nest survival will be challenging, given the propensity of mallards to nest in linear habitats. If the climate change projections materialize in the 21st century, the southeastern portion of the Prairie Pothole Region could become a much more important breeding area for midcontinent mallards. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Wetland occupancy by duck broods in cropland‐dominated landscapes of the United States Prairie Pothole Region

“…brood, duck, occupancy, Prairie Pothole Region, waterfowl conservation, wetland Demographic vital rates of breeding ducks can be affected by landscape conditions (Mack and Clark 2006, Simpson et al 2007, Howerter et al 2014, Koford et al 2016), which has widespread implications for altered landscapes, including the Prairie Pothole Region (PPR) of the north-central United States and prairie Canada where most of the North American ducks breed annually (Batt et al 1989). Extensive wetland drainage and grassland conversion to annual agriculture in this region (Dahl 1990, Doherty et al 2013, Johnston 2013) have reduced the abundance of prairie wetlands and grasslands that provide habitat for breeding ducks (Crissey 1969, Greenwood et al 1995, Walker et al 2013a, Carrlson et al 2018.…”