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Rapidly shifting elevational distributions of passerine species parallel vegetation change in the subarctic

Wiley
Ecosphere
Authors:
  • Denali National Park and Preserve

Abstract and Figures

Despite predictions of poleward and upslope shifts in the distribution of breeding passerines under climate change, studies often report variable responses with some species shifting opposite of the expected direction and others showing range stability. While changes in climate could affect distribution directly, passerines show strong preferences for particular structural vegetation characteristics, suggesting that long-term changes in vegetation may mediate a species' distributional response to climate, and consequently, may be responsible for the observed heterogeneity. We assessed changes in the elevational distribution and occupancy probability of 17 passerine species in Denali National Park, Alaska, from 1995 to 2013 across an elevational gradient containing multiple topographically defined ecotones (treeline and shrubline). An upward distributional shift was pervasive among shrub-tundra species, corresponding with observed expansion of shrub cover at higher elevations. Forest-associated passerines showed a weaker response as a group with some species showing range stability or retraction, while others exhibited modest expansions that were consistent with an advancing treeline ecotone. Denali's mean summer temperature increased significantly over the past century, but remained relatively stable over our study period, implying that longer term changes in climate indirectly influenced bird distribution through changes in woody vegetation. Further, heterogeneity in the response of forest-associated species was consistent with a slower rate of forest development and expansion as compared with shrub colonization. Together, our results indicate that the elevational range dynamics of passerines may be related to species-specific associations with different vegetation communities and variation across these vegetation communities in the timescale over which distributional change is occurring.
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v v Article e012641v
IntroductIon
-
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
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

    
    -
       
      -
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      
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      
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2
1Arctic Network, U.S. National Park Service, 4175 Geist Road, Fairbanks, Alaska 99709 USA
2Central Alaska Network, U.S. National Park Service, 4175 Geist Road, Fairbanks, Alaska 99709 USA
3Denali National Park and Preserve, U.S. National Park Service, 4175 Geist Road, Fairbanks, Alaska 99709 USA
Citation:

Abstract.


 -
 
-
 
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    
-
-

    

  


Key words:
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v v Article e012642v www.esajournals.org
MIZEL ET AL.
-


      
    -

      
Picea glaucaPopulus balsamifera) are


-
    
      

   
-
-
 
    

  -
-

     

      
   -

     
 

-
      
        
-
     

        
-


-
    

    
   -
       
     -
-
-
      
     
    
   
-



-
 

      
  
       
 -
  


       
     




      

       -
     

      
   -

      
      -

-

     

       

-


     

-
    
  -

-

v v Article e012643v www.esajournals.org
MIZEL ET AL.
-



 -
-
        



        


-


    
       




    
     -

    

     -
        
      -
     
     

   
     
 -
      


-
    -
      
   

      
   
-






Methods
Study area
     
        
 
         


     
      
  
     

     
    Picea glauca 
 Betula  Salix    
  Populus balsamifera 
P. glauca   
      
     
     
   
     Dryas

      
      
    
 
       
  
Data collection
     
 
    
      
     
      
      

       -
  
        
   
       
      -
       
v v Article e012644v www.esajournals.org
MIZEL ET AL.
     
       

    
    
      
      
       
        


-
      

     
    -
      
     
  
-





     
     
     

    
      -
       
     -
     -

Statistical analyses
     
       


v v Article e01264v www.esajournals.org
MIZEL ET AL.
      
      
 
      
     -
   
(Zonotrichia leucophrys  
        -
      

       
      -
     
       

     

     
    
     
 ψ   p 
 





 
  2  2
 
 0.88 −1.68   0.74
 
 2.83 −1.32 −1.32

−0.67

1.02

  1.23  −0.68
  0.24





3.64   −1.15
 

 

1.80 −2.05 −0.74

0.67 






 −1.93 

0.57 

 
  −0.76 −0.93
  

 

−2.64 −2.83 0.95 1.37 

 

−5.17  1.39  

  −5.19  0.67  

  −6.40   −0.78
 

  −4.30 −1.34 
  
  −6.20    

 



−2.06 −1.33   
 


3.31 2.19 
 0.69
 
 
  0.54  0.53 

 
 2.54 2.55 1.17  
v v Article e012646v www.esajournals.org
MIZEL ET AL.
      
       -

      
    yt 
     
     zit pt 
pt
 zityt
i 
Ij J
t T
       pt
-

    

  -
 

-



      
et)-

   zit   -
ψit
-
ψit   

δt
αiμ
      
      


      
  
-


       
      
     
     -
     
 
-
     

-

     
       

-
       


  
      -
     
  

-


     -


-

      -
     
         
  -


     
     
    


-


logit
(pijt)=𝛽0+𝛽1dateijt +𝛽2date
2
ijt
+𝛽3timeijt +𝛽4time
2
ijt
+e
obs(ijt)
logit
(𝜓
it
)=𝜇+𝛼
i
+𝛼
1yeart
+𝛼
2elevi
+𝛼
3elev2
i
+𝛼
4yeart
×
elevi
+𝛼
5yeart
×
elev2
i
+𝛿
t
v v Article e012647v www.esajournals.org
MIZEL ET AL.
     

  
-
      

results
       -
     
      
      -
     
       
        -
    
    
     
(Phylloscopus Borealis  
(Passerculus sandwichensis
Zonotrichia atricapilla


 
    
     
    
   Spizella arborea 
 Oreothlypis celata-
      
(Passerella iliaca    
 
 Wilsonia pusilla    

   -
 
Jun-
co hyemalis   Setophaga
coronata coronateCatha-
rus ustulatus
      -
Tur-
dus migratorius 
Regu-
lus calendulaIxoreus naevius)
-

      

Catha-
rus minimusCatharus guatus
Setophaga striata-
     

     
    
       
     
(Melospiza lincolnii   
       

dIscussIon
    

   
       

      

      

      

R2 P 
     

        
     
R2P
v v Article e012648v www.esajournals.org
MIZEL ET AL.
      -
    

     
        
     






v v Article e01264v www.esajournals.org
MIZEL ET AL.
      -
        
   
     
       
       
  


             
          

v v Article e0126410v www.esajournals.org
MIZEL ET AL.
 
       
    
      
    
     
       
 


 
    
   
-
      
    -
      
      
-




    

      
     


    

   


      -
      
    
    -
        
     





  Salix    
       -
     


        


-
-



     
       
-


     

-

-
      
      
-



     
-
      


  -
       
      




      
 

 
-




       -
  
     
    -
       
  
-
v v Article e012641v
IntroductIon
-
-




    
    -
       
      -

      
       
      


2
1Arctic Network, U.S. National Park Service, 4175 Geist Road, Fairbanks, Alaska 99709 USA
2Central Alaska Network, U.S. National Park Service, 4175 Geist Road, Fairbanks, Alaska 99709 USA
3Denali National Park and Preserve, U.S. National Park Service, 4175 Geist Road, Fairbanks, Alaska 99709 USA
Citation:

Abstract.


 -
 
-
 


-
    
-
-

    

  


Key words:
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
v v Article e0126412v www.esajournals.org
MIZEL ET AL.
-
 

     

   -

-
-
-
 
     
   



    
     
     
     
      
     
 
      
     -
  
    
-

-

-



   -
-
     
  



       
     
      -

-
    -

-

 -


AcknowledgMents
       
       
     
        


     
     
      

        
       -
  
  
lIterAture cIted
      in  


  -
     
-

 


 -
    
    


 Phylloscopus   

-
      
-




      


-




v v Article e0126413v www.esajournals.org
MIZEL ET AL.




  
     -
-





       
  
      

-
 -
-


           
-
-



Oreothlypis celataIn
 
     

         
        
    

          



-
  -


-
       
      -


-



      



-


        
-



    
     -
    




-

-
-

        
      
     
 




     

-
 

     
      

-
-

       
-


         
-
-

-
    -
     


-

v v Article e0126414v www.esajournals.org
MIZEL ET AL.
     -

        

     -
-


-
-
      


 
-

       
     
    -

        
 
     

        
  
     -
     
     



 
-

  
      
-

        




  

        
      
-



         
      
     

-




      
     


  
 
-

      
 


     
        
    

         
      -
     

-

-

        



 -



        -
       

   


         -
      -
      

  
-

      

v v Article e01264v www.esajournals.org
MIZEL ET AL.
  

  
      

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
     in 
    -
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   
      -
 in
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supportIng InforMAtIon
        

... Climate warming has brought changes in organismal distribution across all geographical dimensions (elevation/depth, latitude and longitude; Parmesan & Yohe, 2003), although the direction and shape of the response is heterogeneous across species, time and space (e.g. Mizel et al., 2016Mizel et al., , 2021Tingley et al., 2012). Heterogeneity in the response of species' geographical ranges partly reflects the multitude of processes that are conflated in the geographical margins of populations (Hampe & Petit, 2005;Sexton et al., 2009). ...
... Advances in tree-and shrubline (Harsch et al., 2009;Myers-Smith & Hik, 2018) and colonization by tall shrubs along riparian corridors and on hillslopes are evident across the circumpolar Arctic (Myers-Smith et al., 2011;Tape et al., 2006) and Subarctic (Brodie et al., 2019;Frost et al., 2023;Roland et al., 2013Roland et al., , 2016Stueve et al., 2011). Such changes in vegetation structure and composition are expected to affect the distribution of vertebrates (Tape, Christie, et al., 2016;Tape, Gustine, et al., 2016), including passerine birds (Mizel et al., 2016(Mizel et al., , 2021. However, empirical assessments of these responses are both rare and complicated by the need for accommodating fine-scale spatial heterogeneity in the extent of woody vegetation expansion (Dial et al., 2016;Roland et al., 2016;Tape et al., 2012). ...
... Despite the incremental and spatially discontinuous nature of tree-and shrubline advance in Denali, Mizel et al. (2016Mizel et al. ( , 2021 documented rapid upward shifts (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013) in the elevations at which the occupancy probabilities and abundances of shrub-adapted passerines were maximized in the park (hereafter, elevational optima) and suggested that the response was driven by upslope shifts in the distribution of tall shrubs. However, these inferences were drawn from changes in geographical position alone and, consequently, the connections to expanding woody vegetation were only implied, leading to ambiguity concerning the relative roles of conifer and deciduous shrub expansion. ...
Article
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Inferences about the mechanisms of distributional change are often made from simple assessments of variation in the geographical positions of populations. However, direct assessments of species' responses to local habitat change may be necessary for proper understanding of the drivers of distributional dynamics. Amplified climate warming is inducing cascading impacts in boreal‐tundra regions including the expansion of conifers and deciduous shrubs (shrubs). In Denali National Park (Denali), Alaska, passerine birds are exhibiting rapid upslope shifts in distribution but the relative roles of conifer and shrub (woody vegetation) expansion in driving these shifts are unknown. Without directly assessing passerine‐vegetation dynamics, the assumption has been that the observed upslope shifts are indicative of shrub‐adapted passerines tracking the upslope expansion of shrubs. Here, we jointly investigate the processes of conifer and shrub expansion and their relationship to changes in passerine abundance in Denali. We used a remotely sensed vegetation cover timeseries (1985–2020) to assess the topographic and edaphic correlates of conifer and shrub expansion. We then assessed the impacts of changes in shrub and conifer cover on the relative abundance of 12 passerine species (1995–2020). Shrub and conifer colonization rates were highest at intermediate elevations near treeline. However, forest‐ and shrub‐adapted passerines differed in terms of the location in which their response was concentrated relative to treeline. The population growth rates of forest‐adapted passerines exhibited stronger effects of woody vegetation expansion at sites that were initially above treeline (IAT). In contrast, the population growth rates of shrub‐adapted passerines exhibited the negative effects of conifer expansion together with the positive effects of shrub expansion at initially below treeline sites. However, they showed a weak response to woody vegetation expansion at sites that were IAT. Below treeline conifer infilling appears to be pushing the elevational distributions of shrub‐adapted passerines upslope rather than these species following the pull of modest shrub expansion above treeline, as previously assumed. Overall, our findings illustrate the need for explicitly accommodating heterogeneity in habitat change at small spatial scales to properly view the distributional response, particularly when habitat change is concentrated at ecotones.
... Our recovery rate of tagged birds was 9.5%, much lower than the 35% resighting rate of colorbanded Arctic Warblers at a different study site, 210 km east of our study area (Lowther & Sharbough, 2020). Low recapture rates may have resulted from low breeding site fidelity and low survival rates (DeSante et al., 2015;Ralph et al., 1993), geolocators reducing survival (Brlík et al., 2020;Costantini & Møller, 2013), low detectability of tagged birds in the study area, low territoriality of males in the study area, or individual dispersal to new breeding habitat (Hedlund et al., 2017;Mizel et al., 2016). Furthermore, we noted intra-season movements that indicated large territories or inter-territory movements (average = 235 m, range = 85-630; n = 6 banded/tagged birds) that may have contributed to our low recapture rate. ...
... Arctic Warblers are currently altering their breeding range and habitat preference as a result of climate change at their Alaskan breeding grounds (Mizel et al., 2016;Thompson et al., 2016). Thus, this species' risk profile has increased, and we recommend expand- (lead); data curation (supporting); funding acquisition (lead); investigation (equal); methodology (equal); project administration (lead); supervision (lead); visualization (supporting); writing -original draft (supporting); writing -review and editing (supporting). ...
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The Arctic Warbler (Phylloscopus borealis) is a cryptic songbird with an uncommon Nearctic-Paleotropical migratory strategy. Using geolocators, we provide the first documentation of the migratory routes and wintering locations of two territorial adult male Arctic Warblers from Denali National Park and Preserve, Alaska. After accounting for position estimation uncertainties and biases, we found that both individuals departed their breeding grounds in early September, stopped over in southeastern Russia and China during autumn migration, then wintered in the Philippines and the island of Palau. Our documentation of Arctic Warbler wintering on Palau suggests that additional study is needed to document their wintering range. Our results indicate that Arctic Warblers migrate further overwater than previously thought and provides hitherto unknown information on stopover and wintering locations.
... Elevation gradients in high-latitude mountains are spatially compressed so that vegetation transitions from boreal forest to alpine tundra may occur within several hundred meters of elevation change (Roland and Schmidt 2015). In Alaska, there is mounting evidence that elevation range limits of some animals are tracking climate-driven upward shifts in treeline and shrubline (Lloyd and Fastie 2003;Dial et al. 2007;Mizel et al. 2016). As yet, we do not have a clear understanding of how arthropod communities differ across habitats along these compressed elevation gradients or how arthropods will respond to changing vegetation boundaries, but shifts in community composition and dynamics could have significant cascading effects in both boreal and tundra ecosystems. ...
... In a study area that overlaps ours in DNPP, Mizel et al. (2016) reported that passerine birds changed their elevation distribution over a period of eighteen years, with pervasive upward shifts for species associated with the shrub-tundra ecotone and somewhat weaker responses from forest-associated species. The authors surmised that because shrub colonization into the tundra is happening at a faster rate than tree recruitment upslope, birds associated with these different ecotones are responding at comparable rates. ...
Article
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Arthropods at high latitudes and elevations are likely to be vulnerable to effects from climate change such as increased temperatures and shifting vegetation boundaries. Though range shifts northwards and upslope have been reported for many arthropod taxa in temperate latitudes, baseline data needed to track such changes are scarce at northern latitudes. We investigated the influence of climate and vegetation cover on the abundance, diversity, and species composition of pollinators and epigeic arthropods along an elevation gradient in Denali National Park and Preserve, Alaska. We compared arthropods across three habitat types: low-elevation forest, mid-elevation shrubs, and high-elevation tundra along five replicate transects over three years. We collected 35,473 arthropods representing 510 species. Arthropod communities differed distinctly across the three habitat types, with tundra having the highest number of strong indicators and unique species. Elevation, air temperature, and vegetation structure were strong drivers for the ordination of sites. As treeline and shrubline shift upslope with climate change, we predict that distributions of some arthropods will shift to track these habitat boundaries and that tundra-associated arthropods will be most vulnerable as their habitat shrinks. Long-term monitoring of arthropods along elevation gradients at northern latitudes is needed to detect such declines. ARTICLE HISTORY
... The elevation distributions for individual species reflect spatial structure of the boreal bird assemblage but also provide insight into which species may be most at risk of extirpation from the island of Newfoundland because of climate change. In other regions of the boreal forest, many high elevation species have experienced upslope shifts in both their upper and lower elevation boundaries, or downslope shifts in their lower boundary (Mizel et al. 2016, DeLuca and King 2017, Kirchman and Van Keuren 2017. Upslope shifts and range contraction of high elevation species, such as Blackpoll Warbler, Fox Sparrow, and Graycheeked Thrush, could leave them at higher risk of decline or extirpation than species that are abundant across a broader elevational range. ...
... Likewise, systems characterized by shallow climatic gradients over large areas may make it challenging for species to track directional shifts in climate. Furthermore, if climatic shifts outpace habitat or ecotone shifts, species' shifts could be delayed due to structural unsuitability (eg forest specialists in habitats abutting alpine grasslands; Mizel et al. 2016), resulting in an intensifying lean near an abrupt range limit. Species are also responding to contemporary climate change in ways other than redistributing (eg changing the timing of daily activity patterns; Brivio et al. 2024). ...
Article
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Globally, many species’ distributions are shifting in response to contemporary climate change. However, the direction and rate of shifts remain difficult to predict, impeding managers’ abilities to optimize resource allocation. Here, we developed a new approach for forecasting species range‐limit shifts that requires only abundance data along environmental (for example, elevational) gradients. We posited that the distribution of species’ abundances could offer insights into the potential for future range‐limit shifts. We then tested this prediction using data from several transect studies that compared historical and contemporary distributions. Consistent with our prediction, we found that strong asymmetry in abundance distributions (that is, “leaning” distributions) indeed preceded species’ lower‐limit range shifts. Accordingly, surveying abundances along environmental gradients may represent a promising, cost‐effective method for forecasting local shifts. Ideally, this approach will be incorporated by practitioners into species‐specific management planning and will inform on‐the‐ground conservation efforts.
... An increase in preferred land cover (grassland in the fall and shrubland both seasons) might seem beneficial for migration, but it is less clear how Golden-crowned Sparrows would react to synergistic effects of habitat shifts, seasonality, fire, and habitat loss from human development. At a breeding area in Alaska for example, Golden-crowned Sparrows show evidence of shifting to higher elevations, but there is limited potential for shrub habitat to occur above 1200 m in those areas [77]. ...
Article
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Background Migrating passerines in North America have shown sharp declines. Understanding habitat selection and threats along migration paths are critical research needs, but details about migrations have been limited due to the difficulty of tracking small birds. Recent technological advances of tiny GPS-tags provide new opportunities to delineate fine-scale movements in small passerines during a life stage that has previously been inherently difficult to study. Methods We investigated habitat selection along migration routes for a temperate-zone migratory passerine, the Golden-crowned Sparrow ( Zonotrichia atricapilla ), given GPS tags on California wintering grounds. We used a resource selection function combined with conditional logistic regression to compare matched sets of known stopover locations and available but unused locations to determine how land cover class, vegetation greenness and climate variables influence habitat selection during migration. We also provide general migration descriptions for this understudied species including migration distance, duration, and elevation, and repeated use of stopover areas. Results We acquired 22 tracks across 19 individuals, with a total of 541 valid spring and fall migration locations. Birds traveled to breeding grounds in Alaska and British Columbia along coastal routes, selecting for shrubland and higher vegetation greenness in both migration seasons as well as grasslands during fall migration. However, model interactions showed they selected sites with lower levels of greenness when in forest (both seasons) and shrubland (fall only), which may reflect their preference for more open habitats or represent a trade-off in selection between habitat type and productivity. Birds also selected for locations with higher daily maximum temperature during spring migration. Routes during spring migration were lower in elevation on average, shorter in duration, and had fewer long stopovers than in fall migration. For two birds, we found repeated use of the same stopover areas in spring and fall migration. Conclusions Using miniaturized GPS, this study provides new insight into habitat selection along migration routes for a common temperate-zone migrating songbird, contributing to a better understanding of full annual cycle models, and informing conservation efforts. Golden-crowned Sparrows selected for specific habitats along migration routes, and we found previously unknown behaviors such as repeated use of the same stopover areas by individuals across different migratory seasons.
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Mountains hold much of the world’s taxonomic diversity, but global climate change threatens this diversity by altering the distributions of montane species. While numerous studies have documented upslope shifts in elevational ranges, these patterns are highly variable across geographic regions and taxa. This variation in how species’ range shifts are manifesting along elevational gradients likely reflects the diversity of mechanisms that determines elevational ranges and modulates movements, and stands in contrast to latitudinal gradients, where range shifts show less variability and appear more predictable. Here, we review observed elevational range shifts in a single taxonomic group–birds–a group that has received substantial research attention and thus provides a useful context for exploring variability in range shifts while controlling for the mechanisms that drive range shifts across broader taxonomic groups. We then explore the abiotic and biotic factors that are known to define elevational ranges, as well as the constraints that may prevent birds from shifting. Across the literature, temperature is generally invoked as the prime driver of range shifts while the role of precipitation is more neglected. However, temperature is less likely to act directly on elevational ranges, instead mediating biotic factors such as habitat and food availability, predator activity, and parasite prevalence, which could in turn modulate range shifts. Dispersal ability places an intrinsic constraint on elevational range shifts, exacerbated by habitat fragmentation. While current research provides strong evidence for the importance of various drivers of elevational ranges and shifts, testing the relative importance of these factors and achieving a more holistic view of elevational gradients will require integration of expanding datasets, novel technologies, and innovative techniques.
Article
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Breeding bird survey (BBS) data are typically analyzed at the route level in which the average or combined total number of individuals across the 50 stops is treated as a single observation. However, analysis at the stop level may provide information on finer-scale habitat affiliations of species within the broader landscape, as well as changes in species distribution over time. Though once abundant, the Newfoundland Gray-cheeked Thrush (Catharus minimus minimus) underwent a dramatic population collapse across most of the island during the 1980s and 1990s and today is most common in montane forests. The reason for this collapse is not well understood but introduced North American red squirrels (Tamiasciurus hudsonicus), which colonized most forested areas on the island below ~400 m from the late 1970s through the mid-1990s, have been identified as a possible cause. To improve our understanding of changes in the elevational distribution of Gray-cheeked Thrushes, we compared stop-level BBS data from two periods. Our historic period from 1974-1984 corresponds with the initial expansion phase of introduced red squirrels, whereas that from 2000-2015 reflects a period during which the colonization of suitable habitat by squirrels was complete. We used 17 routes (850 stops) where the thrushes had been observed and there were at least 3 surveys completed during each period. Surveys during the 1970s and 1980s indicated that Gray-cheeked Thrushes were abundant at all elevations sampled by the BBS (0-450 m), with higher incidence below 100 m and above 300 m; in contrast, recent surveys indicate that the species is now essentially absent below 350 m. This finding highlights the value of historical stop-level BBS data for reconstructing changes in species distributions and is consistent with the hypothesis that red squirrels have adversely affected Newfoundland Gray-cheeked Thrushes.
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Shrub expansion is among the most conspicuous of the warming-related phenomena occurring within tundra regions, but its effects on vertebrates are not well understood. Among passerines, the habitats of shrub- and tundra-adapted species are expected to increase and decrease, respectively, by roughly equivalent amounts. However, shrub expansion is highly discontinuous, and these predictions are typically based on coarse-scale models of vegetation that permit limited spatial heterogeneity. We used a hindcasting approach to investigate spatial and interspecific heterogeneity in passerine densities through time, as a function of changes in Normalized Difference Vegetation Index (NDVI). We conducted line transect surveys of passerines between 2015 and 2019 at four sites in arctic and subarctic Alaska. Collecting the encounter locations permitted fine-scale assessment of covariates of density. We fit spatial distance sampling models to these data and then used the predicted relationship between passerine density and NDVI to hindcast changes in density since 1999. Our hindcasts suggested limited areal changes in the habitat of tundra-adapted species over the last twenty years while the habitat corresponding to tall shrub–adapted species has likely expanded. Thus, our results contrast with previous predictions due partially to the finer spatial scale of our inference, which allowed for portions of the landscape to resist shrub expansion.
Chapter
The boreal forests of the world, geographically situated to the south of the Arctic and generally north of latitude 50 degrees, are considered to be one of the earth's most significant terrestrial ecosystems in terms of their potential for interaction with other global scale systems, such as climate and anthropologenic activity. This book, developed by an international panel of ecologists, provides a synthesis of the important patterns and processes which occur in boreal forests and reviews the principal mechanisms which control the forests' pattern in space and time. The effects of cold temperatures, soil ice, insects, plant competition, wildfires and climatic change on the boreal forests are discussed as a basis for the development of the first global scale computer model of the dynamical change of a biome, able to project the change of the boreal forest over timescales of decades to millennia, and over the global extent of this forest.
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Bayesian statistics has exploded into biology and its sub-disciplines, such as ecology, over the past decade. The free software program WinBUGS and its open-source sister OpenBugs is currently the only flexible and general-purpose program available with which the average ecologist can conduct standard and non-standard Bayesian statistics. Bayesian Population Analysis Using WinBUGS goes right to the heart of the matter by providing ecologists with a comprehensive, yet concise, guide to applying WinBUGS to the types of models that they use most often: linear (LM), generalized linear (GLM), linear mixed (LMM) and generalized linear mixed models (GLMM). Comprehensive and richly-commented examples illustrate a wide range of models that are most relevant to the research of a modern population ecologist. All WinBUGS/OpenBUGS analyses are completely integrated in software R. Includes complete documentation of all R and WinBUGS code required to conduct analyses and shows all the necessary steps from having the data in a text file out of Excel to interpreting and processing the output from WinBUGS in R.
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We used historic records from 1959 - 99 to explore fire regime characteristics at ecozone scales across the entire North American boreal region (NABR). Shifts in the NABR fire regime between the 1960s/70s and the 1980s/90s were characterized by a doubling of annual burned area and more than a doubling of the frequency of larger fire years because of more large fire events (> 1,000 km(2)). The proportion of total burned area from human-ignited fires decreased over this same time period, while the proportion of burning during the early and late-growing-seasons increased. Trends in increased burned area were consistent across the NABR ecozones, though the western ecozones experienced greater increases in larger fire years compared to the eastern ecozones. Seasonal patterns of burning differed among ecozones. Along with the climate warming, changes in the fire regime characteristics may be an important driver of future ecosystem processes in the NABR.