Agriculture provides food, fuel and fiber to our ever growing human population and is also a major driver of land use change. Small organic farms have the potential to provide habitat for biodiversity while also contributing to food security. Our research examined the characteristics of organic apple orchards associated with habitat use of human-sensitive birds as well as how birds influence production through insect pest control and fruit damage. Because previous research suggests that birds use the interior and edges of agricultural areas differently, we used a stratified study design and conducted transect surveys in small organic farms in western Colorado. We constructed single season occupancy models using program Mark to estimate detection and compare estimates of occupancy among orchard and landscape characteristics (e.g. location, edge ratio and the proportion of surrounding landscape cover). Using the same stratified sampling scheme, we conducted an exclosure experiment to compare fruit damage caused by birds and codling moths, an economically important insect pest. Finally, we observed foraging behavior and used genetic analysis of fecal samples to identify the bird species primarily responsible for crop damage and insect control.
Results/Conclusions
We observed 52 species of birds in apple orchards, over 40% of which are considered human-sensitive. However, human-sensitive species consisted of only 10% of all survey detections. We found that the majority of bird species were detected more frequently in the interior of orchards than at the edges. Habitat use varied by species and species richness varied as a function of location within the orchard and land cover adjacent to the orchards. Rates of both bird damage and insect damage were relatively low, suggesting that birds do not play a significant role in either ecosystem services (pest control) or disservices (fruit damage) in organic apple orchards in our region. Our results demonstrate that organic apple orchards have the potential to provide important habitat for diverse bird communities, including species typically sensitive to anthropogenic 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 quality bird habitat without compromising production.