Assessing bird-mediated ecosystem services and disservices in Colorado apple orchards
Date
2016
Authors
Mangan, Anna Mattern, author
Pejchar, Liba, advisor
Werner, Scott J., committee member
Kendall, William, committee member
Ode, Paul, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Agriculture provides food, fuel and fiber to our growing human population and as the largest terrestrial biomes, crop and pastureland are major drivers of land use change. Small organic farms have the potential to provide habitat for biodiversity while also contributing to food security. My research examined the characteristics of organic apple orchards associated with habitat use of human-adapted and human-sensitive birds as well as how birds influence fruit production positively through insect pest control and negatively through fruit damage. I used a stratified study design to survey birds, observe bird frugivory, capture birds to collect and analyze avian fecal samples, and assess bird and insect damage with an exclosure experiment in small organic farms in western Colorado. I calculated species richness and community similarity among apple blocks and adjacent habitat and evaluated bird habitat use as a function of orchard characteristics (i.e., location in orchard, size of apple block or edge-to-area ratio). I calculated the proportion of bird observations associated with apple frugivory and the proportion of fecal samples that were positive for codling moth DNA to identify bird species that could affect production. I compared bird damage to apples as a function of orchard characteristics and investigated factors that influenced codling moth damage, including access to fruit and moths by birds. I found that organic apple orchards in this region provided habitat for 42 human-adapted and 27 human-sensitive bird species and the bird community in orchards was relatively similar to shrub/tree habitat adjacent to apple blocks. There was sufficient data to model habitat use by seven species; however, use did not vary as a function of the orchard characteristics I measured. Similarly, apple damage by birds and codling moths was consistent within and across apple blocks that varied in size and variety. However, codling moth damage was negatively associated with the exclusion of birds. The molecular technique used to detect codling moth DNA in fecal samples was successful and one species (brown-headed cowbird) had fecal samples positive for codling moth DNA. Five species of birds (Bullock's oriole, common raven, house finch, Lewis's woodpecker, and western scrub-jay) were observed foraging on apples. However, the effect of birds as either agents of fruit damage or pest control in this agroecosystem appeared rather minor. These results demonstrate that organic apple orchards have the potential to provide habitat for diverse bird communities, including species typically sensitive to human activities. Further, because rates of bird-induced fruit damage were low and attributed to a small subset of the avian community, these agroecosystems may provide bird habitat without compromising production.