Long-term landbird monitoring in the National Capital Region National Parks
Date
2023
Authors
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Publisher
University of Delaware
Abstract
Urbanization is increasing globally, altering natural habitat, and leading to habitat loss and fragmentation ultimately resulting in biodiversity loss. National Parks in urbanized areas, such as Washington D.C., act as biodiversity refugia for avian species unable to adapt to a human-dominated landscape. Long-term bird monitoring in these parks, led by the National Park Service Inventory and Monitoring Program, National Capital Region, provides a valuable opportunity to investigate population trends in these urban green spaces, specifically forest and grassland habitats. ☐ Using forest bird monitoring data, I explored trends in annual network-wide occupancy as well as the influence of habitat variables on colonization and local extinction of six forest bird species. I used a hierarchical modeling approach to simultaneously estimate four parameters: initial occupancy, colonization, extinction, and detection probability. I was primarily interested in colonization and extinction and modeled how local and landscape scale variables influence these processes. My results highlight the significance of forest cover as a predictor of forest bird occupancy dynamics. Using derived estimated of annual occupancy, I detected declines in network-wide occupancy of three focal species. ☐ I also assessed the efficiency of the grassland bird monitoring effort to detect 2 % and 3 % annual declines in four grassland species at varying sampling efforts in four National Parks. Using park-level abundance estimates, I conducted power analyses using the R package ‘simr’ and defined a power threshold ≥ 0.80. My results suggest the current grassland sampling effort is sufficient in detecting 3 % declines in annual abundance of my focal species. Except in Antietam National Battlefield, my analysis did not find the sampling scheme to be sufficient in detecting 2 % annual declines.
Description
Keywords
Colonization, Dynamic occupancy, Extinction, National parks, Urbanization, Landbird monitoring