Seaside Sparrow nest location, fate, and nest predator distribution data

Nest failure for coastal marsh bird species is primarily caused by
predation and nest flooding. As sea level rise makes nest flooding more
likely, the threat of nest predation will constrain the potential adaptive
responses of marsh nesting species. Thus, understanding the predictors of
nest predation is important for the conservation of salt marsh-dwelling
bird species, such as Seaside Sparrows (Ammospiza maritima; SESP).
Predator activity may be influenced by landscape features (particularly
habitat edges), potentially making nest predation predictable. We aimed to
understand the predictability of SESP nest predation relative to two major
landscape features: roads and tidal rivers, as both of these edges may be
entryways or attractants for predators in  marshes. In coastal
Georgia, USA, we assessed mammalian predator activity relative to the two
features of interest, and hypothesized that mammalian predator activity
would be greater close to roads and tidal rivers. We also recorded SESP
nest locations and nest predation events and hypothesized that nest
predation events would increase with increasing predator activity.
Consistent with our first hypothesis, mammalian predator activity
increased close to roads and tidal rivers, but mammalian predator
distribution did not explain the spatial variation in SESP nest predation
thus not supporting our second hypothesis. SESP also placed their nests in
locations with high mammalian predator activity, indicating that the
ability to avoid nesting in high-risk areas may be constrained by habitat
or resource limitations. Additionally, mammals may not be the primary nest
predators, as we found that one bird species (Marsh Wren, Cistothorus
palustris) contributed substantially to nest predation rates.
Understanding the predictability of mammalian predator distribution can
allow for focused predator management efforts, such as exclusion, to
habitat edges where we found the highest mammalian predator activity,
which could relax the constraint of nest predation on SESP’s ability to
respond to the intensifying threat of sea level rise.