Data from: Timing of vegetation sampling does not influence associations between visual obstruction and turkey nest survival in a montane forest
Yarnall, Michael; Litt, Andrea; Lehman, Chadwick (2020), Data from: Timing of vegetation sampling does not influence associations between visual obstruction and turkey nest survival in a montane forest, Dryad, Dataset, https://doi.org/10.5061/dryad.g7r412v
Evaluating relationships between ecological processes that occur concurrently is complicated by the potential for such processes to covary. Ground-nesting birds rely on habitat characteristics that provide concealment from predators; this protection often is provided by vegetation at the nest. Recently, researchers have raised concern that measuring vegetation at nest fate introduces a bias, as vegetation at successful nests is measured later in the growing season. This bias can lead to an erroneous conclusion that plant height is positively associated with nest survival. However, if the features that provide concealment are invariant during the incubation period, no bias should be expected, and the timing of measurement is less influential. We used data collected from 98 nests to evaluate whether there is evidence that such a bias exists in a study of wild turkey (Meleagris gallopavo) nesting in a forest ecosystem. We modelled nest survival as a function of visual obstruction and other covariates of interest. At unsuccessful nests, we collected visual obstruction readings at both the date of nest failure and the projected hatch date and compared survival estimates generated using both sets of vegetation data. In contrast to studies in other systems, we found little evidence that the timing of vegetation sampling influenced conclusions regarding the association between visual obstruction and survival; model selection and estimates of nest survival were similar regardless of when vegetation data were collected. The dominant hiding cover at most of our nests was provided by evergreen shrubs; slow growth of these plants likely prevent appreciable changes in visual obstruction during incubation. When considered with a growing body of literature, our results suggest that the influence of timing of sampling depends on the study system. When designing future studies, investigators should consider the structures that provide nest concealment and whether phenology is confounded with nest survival.