Abstract
Understanding the relative impact of climate change and land cover change on changes in avian distribution has implications for the future course of avian distributions and appropriate management strategies. Due to the dynamic nature of climate change, our goal was to investigate the processes that shape species distributions, rather than the current distributional patterns. To this end, we analyzed changes in the distribution of Eastern Wood Pewees (Contopus virens) and Red‐eyed Vireos (Vireo olivaceus) from 1997 to 2012 using Breeding Bird Survey data and dynamic correlated‐detection occupancy models. We estimated the local colonization and extinction rates of these species in relation to changes in climate (hours of extreme temperature) and changes in land cover (amount of nesting habitat). We fit six nested models to partition the deviance explained by spatial and temporal components of land cover and climate. We isolated the temporal components of environmental variables because this is the essence of global change. For both species, model fit was significantly improved when we modeled vital rates as a function of spatial variation in climate and land cover. Model fit improved only marginally when we added temporal variation in climate and land cover to the model. Temporal variation in climate explained more deviance than temporal variation in land cover, although both combined only explained 20% (Eastern Wood Pewee) and 6% (Red‐eyed Vireo) of temporal variation in vital rates. Our results showing a significant correlation between initial occupancy and environmental covariates are consistent with biological expectation and previous studies. The weak correlation between vital rates and temporal changes in covariates indicated that we have yet to identify the most relevant components of global change influencing the distributions of these species and, more importantly, that spatially significant covariates are not necessarily driving temporal shifts in avian distributions.
Highlights
In recent decades, the distributions of many bird species have changed in Britain (Fuller et al, 1995; Thomas & Lennon, 1999), continental Europe (Böhning‐Gaese & Bauer, 1996; Brommer, Lehikoinen, & Valkama, 2012), South Africa (Hockey, Sirami, Ridley, Midgley, & Babiker, 2011), and North America (Sauer, Link, Fallon, Pardieck, & Ziolkowski, 2013)
We found that for both bird species, initial occupancy, coloniza‐ tion rates, and extinction rates correlated with spatial variation in climate and habitat covariates
Our results correlating initial occupancy with environmental covariates are, broadly speaking, consistent with biological expectation and a raft of previous studies that have indicated a significant relationship between species distributions and habitat (Robinson, Wilson, & Crick, 2001; Thogmartin, Sauer, & Knutson, 2007), climate (Barbet‐Massin & Jetz, 2014; Bellard, Bertelsmeier, Leadley, Thuiller, & Courchamp, 2012), or both (Seoane, Bustamante, & Díaz‐Delgado, 2004; Sohl, 2014)
Summary
The distributions of many bird species have changed in Britain (Fuller et al, 1995; Thomas & Lennon, 1999), continental Europe (Böhning‐Gaese & Bauer, 1996; Brommer, Lehikoinen, & Valkama, 2012), South Africa (Hockey, Sirami, Ridley, Midgley, & Babiker, 2011), and North America (Sauer, Link, Fallon, Pardieck, & Ziolkowski, 2013). These shifts are of both ecological and conservation interest, and they have stimulated a great deal of research. We used an analysis of deviance approach to assess the relative impor‐ tance of climate and land cover to the changes in distributions for these two species
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