Detailing predicted changes in the composition of raptor distributions on the Seward Peninsula

Climate change has important implications for raptor distributions (Martínez-Ruiz et al. 2023) and community structure (Gilman et al. 2010, Lurgi et al. 2012) and many impacts are driven by altered landscape characteristics (e.g., Cadieux et al. 2020). Habitat requirements and species interactions dictate raptor distributions and the composition of land cover variables can serve as effective indicators of species species-specific habitat (e.g., Smith et al. 2022). Understanding a species’ distribution is fundamental for conservation (Peterson et al. 2011) and predicting spatial changes in distributions under climate change is critical to understanding impacts on populations and community dynamics (e.g., Parmesan 2006, Zuckerberg et al. 2009, McCaslin and Heath 2020). Arctic climate change is rapidly altering the spatial distributions of raptors and their prey (Booms et al. 2011b) with variation among species (Gilg et al. 2009, Henden et al. 2017). Artic landscape changes are driven by warmer temperatures and altered growing conditions resulting in larger and more widely distributed shrubs (e.g., Betula spp., Salix spp., and Alnus spp.; Sturm et al. 2001, Tape et al. 2006) and the northward encroachment of the boreal forest and the loss of tundra habitat (Boonman et al. 2022). Changing shrub dynamics alters prey communities (Tape et al. 2016) and could have important implications for the Arctic raptor assemblage. Diet niches within the Arctic raptor assemblage overlap, but vary in important ways (Johnson et al. 2022) suggesting that prey base changes could have differential effects. For example, larger riparian areas dominated by shrubs would likely support more song birds (Heath and Ballard 2003), the primary prey of Peregrine Falcons (White et al. 2020). The compounding effects of warmer temperatures and increased prey could make the Peregrine Falcon a more substantial nest competitor for the more specialized Gyrfalcon that is already at risk from climate change (Liebezeit et al. 2012).

To understand drivers of raptor occupancy in the Arctic and predict distribution changes, I propose a multi-step approach. First, I aim to delineate land cover parameters that predict species-specific raptor distributions with a multi-species distribution model (e.g., Lany et al. 2020) for our study area in on the Seward Peninsula (Figure 5). I will summarize land cover variable within species-specific home ranges for which I will attempt to use existing literature to inform home range shape and size (e.g., Watson et al. 2014, Eisaguirre et al. 2016).  I will then forecast distribution models to calculate the current extent of species-specific habitat on the Seward Peninsula. I further aim to forecast landscape changes on the Seward Peninsula based on available scenarios of climate change, predict changes to raptor distributions, and calculate the differences between current spatial extents of species-specific habit and estimates from predictions. Lastly, I will identify areas of conservation interest by locating areas that analyses deemed raptor habitat but lack substrate appropriate for breeding. For raptor occurrence data, I will leverage nearly two decades of spatially explicit aerial survey data on the Seward Peninsula (2005 – current). These analyses will focus on Gyrfalcons, Golden Eagles, Rough-legged Hawks, Peregrine Falcons, and Common Ravens.

   The Seward Peninsula is an ideal study system to understand the effects of changing habitat on an assemblage of raptors because it resides just above the demarcation between sub-Arctic and low Arctic habitats and is experience substantial landscape change. There is significant warming resulting in increased shrubs (Silapaswan et al. 2001), encroachment of the boreal forest (Lloyd et al. 2003), and reduction of permafrost (Debolskiy et al. 2020). Further, the Gyrfalcon population appears to be declining (Franke et al. 2020) with unknown trajectories for the remaining Arctic raptors. The occurrence of breeding Peregrine Falcons, albeit at low density, provides an opportunity to explore whether their population could increase because of climate change and further impact Gyrfalcons. This chapter will provide important drivers of occupancy and give indication of how the composition of the Arctic raptor assemblage may change under climate change.

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