Evaluating breeding bird population changes with forest restoration efforts in New York City
A primary objective of many ecological restoration efforts is to remove invasive plant species to improve ecosystem health. Invasive species removal significantly alters the vegetation structure of local habitats and may temporarily reduce the quality of habitat for wildlife currently using it, which illustrates the trade-offs between long-term ecosystem health and short-term productivity. Short-term impacts may be particularly costly for wildlife populations already in decline. It is well documented that urban parks provide a range of variable environments for habitat refugia, but are also critically degraded by the colonization of invasive plant species. Forest breeding birds across North America are in decline, and altering current habitats may lead to decreases in breeding bird productivity. This study asks a primary research question: What are the short-term impacts of invasive plant species removal on breeding birds? To better understand the risks and impacts on breeding bird diversity and abundance, bird surveys were conducted in Inwood Hill Park, before and after forest restoration efforts. Inwood Hill Park contains the last remaining natural forest in Manhattan, New York City. Bird diversity, abundance, and distribution were geospatially analyzed against restoration sites.
A decade passed between breeding bird surveys to compare metrics before and after forest restoration efforts. Results revealed a significant decrease in breeding bird diversity and abundance following restoration work. There was a dramatic decrease by 43% of confirmed breeding birds. The bird composition in the forest shifted from resident breeding birds to foraging non-breeding birds. This has major implications for an already declining taxonomic group. With little space for urban birds in New York City to establish a new breeding territory in nearby parks, targeted species could be at great risk if their reproduction is limited for many years. This illustrates the potential trade-off between removing invasive plants and improving bird habitat for the future. Further evaluation is needed to understand how restorations ultimately affect bird populations across different time-scales. Improving knowledge of restoration impacts on bird communities provides an opportunity to improve restoration techniques and approaches to limit harmful effects to breeding birds. A follow-up survey is planned for 2016 to examine forest successional influences on bird diversity and breeding territories, and whether breeding bird species observed before restoration activities have returned to the forest or continue to be missing.