Influence of patch shape on mallard nest survival in northern Iowa

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 ± 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 ± 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

Multigene phylogeny of the Mustelidae: Resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation

<p>Abstract</p> <p>Background</p> <p>Adaptive radiation, the evolution of ecological and phenotypic diversity from a common ancestor, is a central concept in evolutionary biology and characterizes the evolutionary histories of many groups of organisms. One such group is the Mustelidae, the most species-rich family within the mammalian order Carnivora, encompassing 59 species classified into 22 genera. Extant mustelids display extensive ecomorphological diversity, with different lineages having evolved into an array of adaptive zones, from fossorial badgers to semi-aquatic otters. Mustelids are also widely distributed, with multiple genera found on different continents. As with other groups that have undergone adaptive radiation, resolving the phylogenetic history of mustelids presents a number of challenges because ecomorphological convergence may potentially confound morphologically based phylogenetic inferences, and because adaptive radiations often include one or more periods of rapid cladogenesis that require a large amount of data to resolve.</p> <p>Results</p> <p>We constructed a nearly complete generic-level phylogeny of the Mustelidae using a data matrix comprising 22 gene segments (~12,000 base pairs) analyzed with maximum parsimony, maximum likelihood and Bayesian inference methods. We show that mustelids are consistently resolved with high nodal support into four major clades and three monotypic lineages. Using Bayesian dating techniques, we provide evidence that mustelids underwent two bursts of diversification that coincide with major paleoenvironmental and biotic changes that occurred during the Neogene and correspond with similar bursts of cladogenesis in other vertebrate groups. Biogeographical analyses indicate that most of the extant diversity of mustelids originated in Eurasia and mustelids have colonized Africa, North America and South America on multiple occasions.</p> <p>Conclusion</p> <p>Combined with information from the fossil record, our phylogenetic and dating analyses suggest that mustelid diversification may have been spurred by a combination of faunal turnover events and diversification at lower trophic levels, ultimately caused by climatically driven environmental changes. Our biogeographic analyses show Eurasia as the center of origin of mustelid diversity and that mustelids in Africa, North America and South America have been assembled over time largely via dispersal, which has important implications for understanding the ecology of mustelid communities.</p

Effects of habitat edges and agricultural practices on waterfowl nest predation in a fragmented prairie landscape

The focus of my research was to study the spacial pattern of waterfowl nest predation in several duck-producing regions of the Canadian prairies. Specifically, I examined the consequences of human-made edges to upland waterfowl nesting success. First, I tested the hypothesis that predation on artificial waterfowl nests was influenced by proximity to edge in different habitat types in the intensively farmed prairie region of Thickwood Hills, Saskatchewan. Data from dense nesting cover revealed higher nest predation near edges compared with the habitat interior. Predation risk was not related to distance (0-150 m) from habitat edge in idle pasture or delayed hay fields. Daily survival rates were highest in dense nesting cover and delayed hay, while idle pasture and rights-of-way exhibited lower nest success. Significantly more mammals than birds depredated waterfowl nests, and the striped skunk (Mephitis mephitis) was the major mammalian predator. The relative importance of the two classes of predators was similar among delayed hay, dense nesting cover and rights-of-ways, but differed in idle pasture where avian predation was higher. Next, I examined the pattern of waterfowl nest predation in two protected wildlife areas of southcentral Saskatchewan, and tested two hypotheses: (1) whether artificial waterfowl nest success was affected by distance from edge, and (2) whether nest success differed between large and small plots. In large plots (200 ha) predation rates were higher along edges compared with the habitat interior. Small plots (50 ha) revealed no significant edge effect. Overall nest success was similar in large and small plots and between spring and summer nesting periods. In large plots, survival was highest in delayed hay fields, intermediate in native grassland, and lowest along rights-of-way. In small plots, survival was higher in native grassland compared with delayed hay. No difference in the pattern of predation at various distances from edge was found between egg-eating mammals and birds. Overall, mammals depredated nests more frequently than birds, and the striped skunk was the major mammalian predator. Last, I examined the effect of edges on survival of natural nests of different species of dabbling ducks at St. Denis National Wildlife Area, Saskatchewan. No effect of distance to edge on nest survival was observed for mallards (Anas platyrhynchos), blue-winged teal (A. discors), gadwall (A. strepera), and other species combined (American wigeon (A. americana), shoveler (A. clypeata), pintail (A. acuta), lesser scaup (Aythya affinis), and green-winged teal (A. crecca)). Nest survival was not affected by proximity to habitat edge in native grassland or managed dense nesting cover habitats, and predation rate was independent of distance to wetlands, roads, or habitat ecotones. The overall distribution pattern of most nests relative to the three edge types was closer to edge than predicted by random models. My results indicate that edge effects are rather weak in an agricultural prairie landscape. The presence of edge effects depends on habitat type, plot size, and predator community. In study areas where mammals are major nest predators, nests along edges in dense nesting cover, and along rights-of-way tend to be subjected to higher predation risk than nests in habitat interiors. (Abstract shortened by UMI.