Diminishing Returns: Results of Black Rail Surveys in Nebraska

The uncertain status of the Black Rail in Nebraska is problematic. Different authors have interpreted existing reports differently resulting in varying conclusions about the species’ status. The exercise of deciphering the limited details of existing reports and litigating their credibility is of little value. The Black Rail is now a threatened species and there is almost no published information on whether it occurs regularly in Nebraska. Furthermore, the species has not been searched for in any consistent form or systematic manner. Without information and understanding about the species’ occurrence, taking actions to benefit and protect this species will undoubtedly be difficult for government and non-governmental agencies or for interested individuals who want to do so. Since 2013, the Nongame Bird Program at the Nebraska Game and Parks Commission has conducted surveys focused on secretive marh birds throughout the state. Although up to eight species were targeted in these specialized surveys, a primary objective was to determine the presence/absence and/or abundance of Black Rails. Here, we report the results from our survey efforts to detect Black Rails in Nebraska

Spring temperatures influence selection on breeding date and the potential for phenological mismatch in a migratory bird

Climate change has affected the seasonal phenology of a variety of taxa, including that of migratory birds and their critical food resources. However, whether climate-induced changes in breeding phenology affect individual fitness, and how these changes might, therefore, influence selection on breeding date remain unresolved. Here, we use a 36-year dataset from a long-term, individual-based study of House Wrens (Troglodytes aedon) to test whether the timing of avian breeding seasons is associated with annual changes in temperature, which have increased to a small but significant extent locally since the onset of the study in 1980. Increasing temperature was associated with an advancement of breeding date in the population, as the onset of breeding within years was closely associated with daily spring temperatures. Warmer springs were also associated with a reduced incubation period, but reduced incubation periods were associated with a prolonged duration of nestling provisioning. Nest productivity, in terms of fledgling production, was not associated with temperature, but wetter springs reduced fledging success. Most years were characterized by selection for earlier breeding, but cool and wet years resulted in stabilizing selection on breeding date. Our results indicate that climate change and increasing spring temperatures can affect suites of life-history traits, including selection on breeding date. Increasing temperatures may favor earlier breeding, but the extent to which the phenology of populations might advance may be constrained by reductions in fitness associated with early breeding during cool, wet years. Variability in climatic conditions will, therefore, shape the extent to which seasonal organisms can respond to changes in their environment.Peer reviewedIntegrative Biolog

Spring temperatures influence selection on breeding date and the potential for phenological mismatch in a migratory bird

Climate change has affected the seasonal phenology of a variety of taxa, including that of migratory birds and their critical food resources. However, whether climate-induced changes in breeding phenology affect individual ftness, and how these changes might therefore influence selection on breeding date remain unresolved. Here, we use a 36-yr dataset from a long-term, individual-based study of House Wrens (Troglodytes aedon) to test whether the timing of avian breeding seasons is associated with annual changes in temperature, which have increased to a small but signifcant extent locally since the onset of the study in 1980. Increasing temperature was associated with an advancement of breeding date in the population, as the onset of breeding within years was closely associated with daily spring temperatures. Warmer springs were also associated with a reduced incubation period, but reduced incubation periods were associated with a prolonged duration of nestling provisioning. Nest productivity, in terms of fledgling production, was not associated with temperature, but wetter springs reduced fledging success. Most years were characterized by selection for earlier breeding, but cool and wet years resulted in stabilizing selection on breeding date. Our results indicate that climate change and increasing spring temperatures can affect suites of life-history traits, including selection on breeding date. Increasing temperatures may favor earlier breeding, but the extent to which the phenology of populations might advance may be constrained by reductions in ftness associated with early breeding during cool, wet years. Variability in climatic conditions will, therefore, shape the extent to which seasonal organisms can respond to changes in their environment

Quantifying multiple breeding vital rates in two declining grassland songbirds

Many studies of reproductive success in North American songbirds have focused on nesting success, while relatively few have evaluated breeding-season adult survival and post-fledging survival. Grassland songbirds are among North America's most rapidly declining avian groups, and knowledge of factors that influence vital rates is needed to address declines, develop management strategies, and accurately model population limitation. We concurrently monitored nesting success, breeding-season adult survival, and post-fledging survival of two grassland obligates, Baird's Sparrow and Grasshopper sparrow, breeding in western North Dakota and northeastern Montana. Nesting success was monitored by locating and visiting nests at regular intervals while adult and post-fledging survival were assessed by daily telemetry tracking of radio-tagged birds. We analyzed the three variables using logistic exposure and modeled climate, temporal, and vegetative covariates to explain variation in rates. Cumulative nesting success, breeding-season adult survival, and post-fledging survival were 37%, 78%, and 25%, respectively, for Baird's Sparrow and 16%, 74%, and 55% for Grasshopper Sparrow. Both nesting success and post-fledging survival in Baird's Sparrow were responsive to environmental covariates including temporal effects and vertical vegetation structure. Conversely, vital rates of Grasshopper Sparrow were largely unresponsive to covariates we modeled, perhaps because of the species' broader habitat niche relative to Baird's Sparrow. Breeding season adult survival in both species showed little annual variation and was high relative to overwintering survival estimates for the same species, while post-fledging survival in Baird's Sparrow was low and may be a management concern. We suggest as a next step the formal comparison of vital rates across life-stages in an integrated population model capable of identifying sources of population limitation throughout the full annual cycle of the species