The Influence of Habitat on Nest Survival of Snowy and Wilson's Plovers in the Lower Laguna Madre Region of Texas
Snowy Plovers (Charadrius alexandrinus) and Wilson’s Plovers (Charadrius wilsonia) are two shorebird species that nest along the Gulf Coast of the US. We modeled the daily nest survival of both species in the lower Laguna Madre region of Texas during the 2003 and 2004 breeding seasons as a function of nest age, year, day in the season, maximum daily temperature, daily precipitation, and habitat features at three spatial scales (microhabitat, a 25-m radius of the nest, and landscape). Daily survival of Snowy Plover nests increased with nest age ( Age = 0.03, 95% confi dence limits were –0.01, 0.07, on a logit scale), but did not vary between years. Nests inland had substantially lower daily survival than nests on the coast ( Inland = –0.18, 95% confi dence limits were –1.03, 0.67, on a logit scale). The presence of a conspicuous object at the nest site increased daily nest survival. A quadratic trend occurred on the coeffi cient of variation (CV) for low vegetation (CV used as an index of low vegetation spatial heterogeneity) at the 25-m scale for Snowy Plover nests. Daily nest survival of Wilson’s Plovers was best explained by a combination of two habitat metrics at the microhabitat scale. Less vegetation at the immediate nest site increased daily survival ( Veg = –1.35, 95% confi dence limits were –2.28, –0.42, on a logit scale) while daily nest survival was higher for nests with lower contagion at the microhabitat scale ( Contagion = –0.87, 95% confi dence limits were –1.65, –0.10, on a logit scale). We found no evidence for yearly differences or an effect of weather on the daily nest survival of either species. Our results illustrate the role that selected habitat features play in the nest survival of Snowy and Wilson’s plovers and further our understanding of their nesting ecology. We anticipate that our results will assist in the identifi cation and protection of habitats critical to breeding populations of these and other shorebird species.