Kuletz and others 



Chapter 15 



Inland Habitat Suitability in Southcentral Alaska 



Table 6 Logistic regression model to predict probability of occupied sites of Marbled Murrelets (sites where one 

 or more behaviors indicating nesting were observed) for the three study sites: western Prince William Sound (1992), 

 Kenai Fjords National Park (1993) andAfognak Island (1992), Alaska (n = 152 sites total) 



possible that high detection rates result from murrelets 

 funneling through bay heads and using them as flyways. 

 However, the consistency of high activity at bay heads for 

 the study areas overall, combined with the high proportion 

 of occupied sites at bay heads, suggests otherwise. 



Marks and others (in press) found that murrelet activity 

 was positively correlated with stand size in western Prince 

 William Sound. High activity at bay heads may be a result of 

 larger contiguous forests at bay heads, although stand size 

 relative to landform has not been investigated in these areas. 

 Microclimate and minimal exposure to weather at bay heads 

 may foster characteristics associated with known murrelet 

 nesting habitat, including large tree size and mossy platforms 

 on trees. This may explain the larger tree d.b.h., greater 

 number of potential nesting platforms, and higher percentage 

 of epiphyte cover at sites located at heads of bays relative to 

 more exposed sites. However, these trends were not evident 

 at Kenai Fjords National Park in earlier analyses (Kuletz and 

 others 1994b). This is likely due to the recent deglaciation of 

 many of the bay heads. 



The importance of tree size and elevation in predicting 

 murrelet activity has been suggested by other studies. Murrelets 

 typically nest in old-growth stands where trees tend to be 

 relatively large (see Hamer and Nelson, this volume b). 

 Hamer and Cummins (1991) and Rodway and others (1991) 

 found that murrelet activity was highest in low elevation 

 forests in Washington and British Columbia. In northern 

 latitudes, larger trees are found at lower elevations (Viereck 

 and Little 1972). Kuletz and others (in press) found a significant 

 negative correlation between tree d.b.h. and elevation on the 

 Naked Island group, even though the highest elevation was 

 <460 m. Thus, the contribution of elevation to the model is 

 likely due to its effect on patterns of vegetation growth. 



Conversely, it is also possible that murrelets are detected 

 more frequently at low elevations, as they move from marine 

 to terrestrial areas, because low elevation habitat tends to be 

 closer to shore. Murrelets must pass over the shoreline to 

 reach sites further inland. However, in some areas, murrelets 

 leave the water and rapidly gain altitude before flying to 

 distant inland sites (Van Vliet, pers. comm.), and would not 

 be detected along the shoreline. 



Responses of murrelet activity to variation in slope, 

 aspect, and canopy cover were not consistent, and may have 

 been influenced by local geography. Activity was positively 

 related to northerly aspect in preliminary regression models, 

 similar to findings of earlier analyses for Naked Island data. 

 At Naked Island, there was a non-significant positive trend 

 of higher murrelet activity on northerly slopes, possibly due 

 to more high- volume forests on these slopes or the prevalence 

 of southeast winds, that murrelets may seek to avoid (Kuletz 

 and others, in press). 



Occurrence of Occupied Behaviors 



The influence of habitat features on the occurrence of 

 occupied behaviors was similar to their influence on murrelet 

 activity levels. In particular, the size of trees and the number 

 of potential nest platforms were good predictors of murrelet 

 occupied behavior. This is consistent with Alaskan tree nests 

 that have been documented; most were located on large 

 moss-covered platforms, often on the largest trees in an area 

 (Naslund and others, in press). However, our results could 

 be biased in that occupied behaviors in non-forested habitats 

 have not been adequately defined. 



Epiphyte cover, number of potential nest platforms, and 

 tree size were clearly related. The importance of these habitat 

 features to nesting murrelets may vary geographically. For 

 example, epiphyte cover may be more important in Alaska 

 than in other areas; moss was not the primary nest substrate 

 of some nests at lower latitudes (Hamer and Nelson, this 

 volume b; Singer and others 1991). Naslund and others (in 

 press) suggested that moss is more important as insulation in 

 Alaska's severe climatic conditions. Additionally, moss 

 increases platform size, which could be important where 

 small trees predominate. 



Nesting clearly occurs in non-forested areas (Day and 

 others 1983). However, the extremely low levels of general 

 activity and of occupied behaviors at non-forested sites suggest 

 that nesting activity in non-forested areas is less common than 

 in forested areas. We believe that our results indicate that 

 murrelet nesting density is low in sparsely forested or non- 

 forest areas and that such habitat is of less importance to the 

 population. However, it is possible that differences in murrelet 



148 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



