Highway effects on artificial nest survival in a neotropical sand-coastal plain: a spatiotemporal approach

Roads are a leading cause of habitat fragmentation and may reduce bird populations by increasing nest predation rates. However, few studies have investigated the effects of traffic volume on the reproductive success of roadside birds in the neotropics. Our goal was to evaluate the effects of spatial, temporal, and vehicle flow variations on the survival of artificial open-cup nests. The study was carried out in a nature reserve on the side of a highway during the breeding season (from October to March) in two restinga (sand-coastal plain) phytophysiognomies in southeastern Brazil: non-floodable (open) and floodable (closed). One hundred thirty nests were distributed along transects ranging from 3 m to 300 m from the highway in each vegetation type (totaling 260 nests). The nests were checked every three days for their status (depredated or intact) over 12 days, and new nests were subsequently placed near sampling points of depredated or successful nests. We estimated survival using logistic exposure generalized linear and additive mixed models. At the end of the 180 days of the experiment, 33% of 6202 nests were successful. Nest survival was higher in open restinga than in closed restinga. In both habitats, nest survival was lowest mid-season and highest at the beginning and end. Survival rates peaked near the highway, declined up to 50 m away, then showed a slight increase. Finally, survival increased at moderate-to-high traffic volumes (~22,000 vehicles/day), particularly in open restinga. We suggest that spatial, temporal, and habitat-specific highway impacts (e.g., noise, vibration, visual stimuli) can lead to variations in the activity of nest predators, generating fluctuations in nest survival associated with predator behavior.