Imperiled sparrows can exhibit high nest survival despite atypical nest site selection in urban saltmarshes

Understanding habitat selection and its fitness consequences in remnant populations of birds in fragmented and urbanized habitat may provide guidance to land managers for imperiled species conservation. We studied Saltmarsh Sparrow, Ammospiza caudacuta, and Seaside Sparrow, A. maritima, nest site selection and nest survival at five sites in New York City (NYC) and one site on western Long Island, New York in 2012 and 2013. We compared marsh vegetation and nest structure characteristics between our study sites and other studied sites for these species in the Northeastern United States. Saltmarsh Sparrows in NYC selected nest sites with the tall form of low-elevation marsh grass (at two sites this was above the proportion available), which is atypical for this species, and Seaside Sparrows selected an upland shrub species at one site, possibly to compensate for a lack of tall low-elevation marsh grasses. Daily nest survival at New York sites increased with nest height above the ground for both species, contrary to previous studies for Saltmarsh Sparrows in intact habitat. Mean nest height for both species was found to be taller in NYC than at other studied locations, and NYC sites may have had taller than average vegetation available, indicating that these sparrows may be able to adapt to some changing marsh characteristics. The difference in nest site selection observed in NYC populations from published studies did not appear to have a cost to nest survival in at least one year. Although high-elevation marsh is the optimal habitat restoration target for Saltmarsh Sparrows, it may be difficult to create in small, urbanized marshes, and our results suggest that other approaches may be successful. A mix of substrates and vegetation heights may allow sparrows to exhibit variation in nest site selection and promote nest survival in the face of changing limiting factors

Data from: Quantifying the importance of geographic replication and representativeness when estimating demographic rates, using a coastal species as a case study

Demographic rates are rarely estimated over an entire species range, limiting empirical tests of ecological patterns and theories, and raising questions about the representativeness of studies that use data from a small part of a range. The uncertainty that results from using demographic rates from just a few sites is especially pervasive in population projections, which are critical for a wide range of questions in ecology and conservation. We developed a simple simulation to quantify how this lack of geographic representativeness can affect inferences about the global mean and variance of growth rates, which has implications for the robust design of a wide range of population studies. Using a coastal songbird, saltmarsh sparrow (Ammodramus caudacutus), as a case study, we first estimated survival, fecundity, and population growth rates at 21 sites distributed across much of their breeding range. We then subsampled this large, representative dataset according to five sampling scenarios in order to simulate a variety of geographic biases in study design. We found spatial variation in demographic rates, but no large systematic patterns. Estimating the global mean and variance of growth rates using subsets of the data suggested that at least 10-15 sites were required for reasonably unbiased estimates, highlighting how relying on demographic data from just a few sites can lead to biased results when extrapolating across a species range. Sampling at the full 21 sites, however, offered diminishing returns, raising the possibility that for some species accepting some geographical bias in sampling can still allow for robust range-wide inferences. The sub-sampling approach presented here, while conceptually simple, could be used with both new and existing data to encourage efficiency in the design of long-term or large-scale ecological studies