Impact of Restoration on Birds at Powell Butte Nature Park
OVERVIEW
Powell Butte Nature Park (PBNP) is a former homestead and dairy farm purchased by the City of Portland, OR in 1925 and later converted into a nature park by Portland Parks & Recreation (PP&R) in 1987. Sitting atop two 50-million gallon underground reservoirs managed by the Portland Water Bureau, the 611 acre nature park includes a variety of upland forest and grassland habitats. Upon completion of the second underground reservoir in 2015, PP&R began to conduct significant habitat improvements in the park including the creation and/or restoration of approximately 210 acres of open prairie and oak-savannah habitat. Our research at PBNP will focus on grassland bird populations in restored prairie habitat and thus will provide valuable information on the success of past and future restoration efforts over time. Many grassland bird species are of high conservation concern due to the extensive loss and/or degradation of prairie habitat in the United States and worldwide. Of 46 grassland-breeding birds found in the United States, almost half are of conservation concern and report significantly declining populations. In Oregon’s Willamette Valley it is estimated that less than one percent of the original extent of prairie habitat remains with most converted for farming or development. Most of the remaining prairie habitat in the Willamette Valley occurs in small patches such as the restored prairie at PBNP, and such isolated patches are important refuges for the persistence of many grassland bird communities.
Long-term monitoring of the impacts of restoration projects on wildlife populations is often not included in habitat restoration plans. However, monitoring of physical and biological response variables to restoration treatments is important to: 1) document and measure the effects of restoration actions; 2) evaluate responses with respect to expected outcomes; and 3) contribute to the science and practice of restoration ecology. Our research focuses on the response of grassland bird populations; however, we will also collect data on the overall landbird community at PBNP in order to provide additional information regarding the success of restoration efforts. We are monitoring landbird populations using a demographic study of focal grassland bird species in restored prairies and a Community Science (or Citizen Science) study collecting data on the overall landbird community found at the nature park.
Our research includes three main monitoring objectives to measure the response of landbird communities to habitat restoration actions at PBNP: 1) quantify the numerical response in species abundance by breeding, migrating and wintering landbirds (passerines and raptors); 2) quantify changes in demographic rates of focal grassland bird species breeding in restored prairie habitat over time as restoration advances; and 3) develop a species list and characterize bird community composition and abundance at PBNP using Community Science. We expect that the grassland bird community should become more diverse over time as restoration advances, and that the abundance of grassland obligate species (e.g., Western Meadowlark Sturnella neglecta) should increase. We also expect that demographic rates for grassland birds already breeding at PBNP (e.g., Savannah Sparrow Passerculus sandwichensis) should increase as prairie habitat is expanded and improved further via removal of woody vegetation and control of invasive plants. Finally, we expect that the overall landbird community at PBNP should become more diverse and that the park should support a greater abundance of many landbird species.
PROJECT PARTNERS
Johnson Creek Watershed Council
https://www.facebook.com/JohnsonCreekWC/
Portland Parks & Recreation
https://www.facebook.com/PortlandParks/
Portland Water Bureau
https://www.portland.gov/water
Portland Bureau of Environmental Services
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