Influence of hiking trails on montane birds

Abstract

Montane forests contribute significantly to regional biodiversity. Long-term monitoring data, often located along hiking trails, suggests that several indicator species of this ecosystem have declined in recent decades. Declining montane bird populations have been attributed to anthropogenic stressors such as climate change and atmospheric deposition. Several studies from montane systems have also documented decreased estimates of abundance and reproductive success as well as altered singing rates near hiking trails. Therefore, recreational hiking may be contributing to montane bird population declines and potentially biased population estimates because of trail avoidance or altered detection probabilities near trails. We studied the effect of hiking trails on the abundance, seasonal movements, and detection probabilities of montane birds in the White Mountains, New Hampshire in 2006 and 2007. We used hierarchical, generalized N-mixture models that account for imperfect detection probabilities to examine the effects of recreational hiking on bird communities. We also examined the potential effects of hiking on the reproductive success of a boreal forest songbird, blackpoll warbler (Setophaga striata). We found little evidence to suggest hiking trails influence abundance, detection probabilities, or within and among seasonal movements of montane forest birds. We also found no evidence to suggest daily nest survival of blackpoll warbler nests vary with distance from trail. Our study suggests that recent increases in hiking traffic are unlikely to have caused declines in montane birds in this region. Furthermore, our results provide evidence that trail-based monitoring programs can provide accurate and efficient estimates of abundance for some montane forest bird species in the White Mountains of New Hampshire.