The effects of human disturbance on birds in Bastrop State Park

Abstract

With rapidly disappearing natural areas due to development and fragmentation, public lands provide important habitat for birds. However, the increasing use of public lands for recreation may decrease the value of these areas for bird use. Human disturbance can damage birds in many ways, including disrupting foraging or social behavior, increasing nest predation, interfering with parent-offspring and pair bonds, increasing nesting failures, and reducing the viability of fledglings. Additionally, birds may perceive humans as predators and leave an area, and the resulting decline in species abundance resembles the effects of habitat loss. Increased human outdoor activity has created the need for information regarding the effects of human disturbance on birds. I investigated the effects of human disturbance on birds in Bastrop State Park (BSP) in central Texas in 1998 and 1999. A wide variety of people use much of BSP, and many areas within the park experience significant amounts of disturbance from people and vehicles, particularly in campgrounds. I evaluated the effects of various types of human disturbance on the presence of 20 avian species, including seven neotropical migratory species. Brown-headed Cowbird (Molothrus ater), Mourning Dove (Zenaida macroura), Carolina Wren (Thryothorus ludovicianus), and Summer Tanager (Piranga rubra), were sensitive to human presence, and Blue Jays (Cyanocitta cristata), and Downy Woodpeckers (Picoides pubescens) occurred in lower abundances in sites with higher numbers of vehicles. However, other species (e.g., American Crow [Corvus brachyrhynchos], Black-and-white Warbler [Mniotilta varia], Pileated Woodpecker [Dryocopus pileatus], Red-eyed Vireo [Vireo olivaceus], Ruby-throated Hummingbird [Archilochus colubris], White-eyed Vireo [Vireo griseus], and Yellow-billed Cuckoo [Coccyzus americanus]) tolerated humans, vehicles, or both. Neotropical migratory species did not show higher sensitivity to disturbance when compared to resident species, and forest interior species were not more sensitive than edge species. My results indicate that some species, including migrants, can become habituated to human presence in protected areas with low harassment and low-intensity, predictable disturbances. Management recommendations for BSP include protecting habitat, minimizing human disturbance in some areas, providing buffer zones between humandominated zones and sites containing vulnerable species, and softening edges in campgrounds.