• Altered Distribution - overwintering moose and ptarmigan most likely 

 responded to the reduction of food and cover habitat provided by 

 floodplain thickets, by either increasing their winter reliance upon 

 adjacent undisturbed thickets, or by shifting their local winter 

 distribution and movement patterns. 



• No Apparent Response - large mammals (such as caribou, bears, and 

 wolves) showed no significant response to floodplain alterations 

 created by gravel removal operations. 



Population Reductions 



At 18 of the 25 study sites significant areas of vegetated habitat were 

 removed prior to gravel mining. These habitats usually were of advanced or 

 mature vegetative stages and were dominated by a diverse and abundant passer- 

 ine and small mammal community in all four regions. In Southern and Northern 

 Interior regions red squirrels also were dominant members of these commu- 

 nities at sites that contained stands of mature spruce, or mixed spruce and 

 b irch. 



On the North Slope and Seward Peninsula, the passerine populations 

 inhabiting riparian shrub thickets most frequently were dominated by yellow 

 warblers, Wilson's warblers, orange-crowned warblers, white-crowned spar- 

 rows, fox sparrows, tree sparrows, gray-cheeked thrush, American robins, 

 common redpol Is, and ye I low wagtai Is. Although population sizes were not 

 estimated, at sites with extensive development of riparian shrub thickets as 

 many as 50 individual birds of 13 species were present in an area of approxi- 

 mately 3.5 ha (Penny River). In Southern and Northern Interior sites, many 

 of the above passerines were joined by ye I I ow-r umped warblers, gray jays, 

 black-capped chickadees, dark-eyed juncos, and alder flycatchers. 



At many sites small mammals also were common to abundant in heavily 

 vegetated habitats. Tundra voles were the most frequently captured species, 

 and were recorded in all four regions. They were captured in a wide variety 

 of vegetated habitats and appeared to be more tolerant than other small 

 mammals of the low-lying habitats which frequently contained water saturated 



250 



