Linking Alaska's Predicted Climate, Gyrfalcon, and Ptarmigan Distributions in Space and Time: A Unique 200-Year Perspective.

Abstract

ABSTRACT.-Gyrfalcons (Falco rusticolus), Rock Ptarmigan (Lagopus muta), and Willow Ptarmigan (L. lagopus) are quintessential Arctic species that are closely linked within the Arctic ecosystem. They likely face similar challenges in the face of rapid changes to their Arctic climate. Gyrfalcons in particular may be most challenged by rapid climate change because of their relatively specialized ecological niche, small population size, and K-selected life history strategy. Given this situation, we were interested in predicting how the distribution of these species may change under current climate predictions. Therefore, we modeled the fundamental niche of each species in relation to temperature and precipitation in space and time across 200 years in Alaska (1900-2100). Though the realized niche will ultimately determine where species are distributed in the future, we interpreted our predictions as representing the areas in which environmental conditions will allow the species to occur. We were interested in the large-scale, climate-induced trends in expansion, contraction, and overlap of these areas over time.We used the Scenarios Network for Alaska Planning (SNAPs) regionalized/downscaled decadal mean June and December temperature and precipitation predictions from the A1B scenario, and as proposed by the United Nations Intergovernmental Panel on Climate Change (IPCC), to forward-model distributions from 2009-2099 in 30-year intervals. We used historical temperature and precipitation measurements from 1900-2006 to backwards-model the distribution of the species' fundamental niche to qualitatively assess forward-modeling predictive accuracy.Forward-models predicted that the fundamental niches of Gyrfalcons and ptarmigan will contract spatially, and backwards-models suggested that they have contracted in the past as Alaska's climate has warmed. Over the 200-year period, the total geographic area over which the species' fundamental niches were predicted to occur decreased overall by 20% (Willow Ptarmigan), 40% (Rock Ptarmigan) and 60% (Gyrfalcon). The distribution of the predicted fundamental niche of each species also became more fragmented, and the percent of spatial overlap between predicted presence of Gyrfalcons and ptarmigan declined over time. These alterations may affect the species' long-term viability and co-evolution and will likely influence important biological processes such as dispersal, genetic diversity, predator-prey dynamics, and basic behavior. Predicted shifts in the geographic distribution of their fundamental niches may have cascading effects on other species, communities, and systems. For science-based, pro-active, adaptive management, 177

Status and trends of tundra birds across the circumpolar Arctic

“…Overall, Arctic peregrine populations now appear stable, with reports of a northward expansion among peregrines in Northwest Greenland (Burnham et al 2012), as well as an advancing timing of breeding in several Arctic regions (Franke 2020), likely as a consequence of climate change. Gyrfalcon populations are also stable, although poaching is an increasing concern in some areas (Potapov 2011), and shrubification and a shrinking High Arctic climate zone may pose challenges in the future, mediated through impacts on their primary prey, ptarmigan (Booms et al 2011). The iconic snowy owl is believed to be declining range-wide, and was recently uplisted by IUCN to a status of vulnerable (Birdlife International 2018).…”

Body condition and reproductive phenology

“…At the population level, long-term monitoring of pre-laying physiological condition could provide insight into how changes in prey availability affect reproduction in Gyrfalcons. Ptarmigan are particularly important prey for Gyrfalcons as they are likely the only source of food available during the pre-laying period (Booms et al 2008(Booms et al , 2011). Moreover, model-based predictions on spatial distribution of Gyrfalcons and both Rock (Lagopus muta) and Willow Ptarmigan (Lagopus lagopus) predict a decrease in the range of these species (Huntley and Green 2011), as well as in the spatial overlap between the Gyrfalcon and their prey over the coming decades (Booms et al 2011) as a result of predicted climate change.…”

“…Ptarmigan are particularly important prey for Gyrfalcons as they are likely the only source of food available during the pre-laying period (Booms et al 2008(Booms et al , 2011). Moreover, model-based predictions on spatial distribution of Gyrfalcons and both Rock (Lagopus muta) and Willow Ptarmigan (Lagopus lagopus) predict a decrease in the range of these species (Huntley and Green 2011), as well as in the spatial overlap between the Gyrfalcon and their prey over the coming decades (Booms et al 2011) as a result of predicted climate change. Concerns for delayed reproduction in Gyrfalcons as a consequence of collapsing ptarmigan abundance cycles in Yukon, Canada, have already been expressed (Mossop 2011).…”

Spatial distribution of Svalbard rock ptarmigan based on a predictive multi-scale habitat model

“…Zohmann et al (2013) suggested combining habitat suitability with abundance data of rock ptarmigan from different points in time to evaluate changes in habitat suitability and species distribution over time. Booms et al (2011) assessed changes in rock ptarmigan and gyrfalcon habitat suitability (fundamental niches) over a 200-year time-period and detected substantial environmental changes influencing long-term population viability and predator-prey interactions. Finally, Pedersen et al (2012) stratified survey sites for long-term population abundance monitoring according to habitat with the studies of Unander and Steen (1985) and with rock ptarmigan habitat requirements in other distant parts (e.g.…”