evident difference was in the overstorj* layer where 

 shrub biomass, shrub canopy cover, and shrub 

 height means were higher on the beaver pond site. 

 Shrub height and shrub biomass values in the 

 beaver pond habitat were about twice those of the 

 nonponded area. Differences in the shrub compo- 

 nent were predominantly due to the abundance 

 of willows that were found throughout the beaver 

 pond complex. Photographic evidence shows a pro- 

 nounced enlargement of the willow stand since the 

 construction of the beaver dams (Anderson 1989). 

 Before dam construction, willows formed only a 

 narrow band along the stream. 



Differences between the two areas were also found 

 in the herbaceous layer where graminoid biomass 

 and graminoid height means were higher in the 

 beaver pond habitat (table 1). The differences 

 seemed to be mostly due to thicker and taller stands 

 of grasses and sedges, predominantly beaked sedge, 

 that grew on the moist sites near the beaver pond. 

 Presumably, those responses were caused by a 

 higher water table near the beaver impoundments. 

 Forbs exhibited no differences in canopy cover, 

 height, or biomass means between study plots. 



We recorded 13 breeding bird species on the 

 Summit Creek study plots (table 2). The most 



Table 2 — Density (number/ha), diversity, and otiier attributes of breeding bird populations in a beaver- 

 pond complex (willow) and adjacent (nonwiilow) riparian habitat, Summit Creek, ID, 1989 



Density 





Foraging 



Nesting 



Beaver pond 



Adjacent 



Species 



guild^ 



guild^ 



(willow) 



(nonwiilow) 



■✓III J _ 

 Killdeer 



/-^ 1 

 C3C3I 







i 3 



(Charadrius vociferus) 













SGI 



GRN 



.22 



0.00 



{Actitis macularia) 











Common snipe 



GPV 



GRN 



.09 



.00 



(Gallinago gallinago) 











Willow flycatcher 



ASI 



BTN 



1.04 



.00 



{Empidonax traillii) 











American robin 



GOV 



BTN 



.07 



.00 



( Turdus migratorius) 











Yellow warbler 



LGI 



BTN 



1.22 



.00 



{Dendroica petechia) 











Common yellowthroat 



LGI 



GBN 



.09 



.00 



(Geothlypis trichas) 











Vesper sparrow 



GFO 



GRN 



.11 



.42 



(Pooecetes gramineus) 











Savannah sparrow 



GFO 



GRN 



2.16 



1.96 



(Passerculus sandwichensis) 











Song sparrow 



LFO 



GBN 



.33 



.00 



{Melospiza melodia) 











Red-winged blackbird 



GFO 



CRN 



.20 



.60 



{Agelaius phoeniceus) 











Western meadowlark 



GGI 



GRN 



.27 



.40 



(Stumella neglecta) 











Brewer's blackbird 



GFO 



GBN 



4.09 



+ 



(Euphagus cyanocephalus) 











Total number/ha 







10.11 



3.38 



Biomass (g/ha)* 







422 



121 



Species richness (n) 







13 



4 



Species diversity^(1/Xp,^) 







4.21 



2.52 



' After DeGraaf and others (1985). GGI = ground gleaning insectivore, SGI = shoreline gleaning insectivore, 

 GPV = ground probing vermivore, ASI = aerial-sally feeding insectivore, GGV = ground gleaning vermivore, 

 LGI = lower-canopy gleaning insectivore, GFO = ground foraging omnivore, LFO = lower-canopy and ground 

 foraging omnivore. 



Wter Harrison (1979). GRN = ground nester, BTN = bush and small tree nester, GBN = ground and bush 

 nester, CRN = cattail, rush, sedge, reed, grass, and bush nester. 

 ^+ indicates the bird was observed infrequently. 

 'Species weights from Dunning (1984). 



'After Hill (1973). Here, is the proportional abundance of the Kh species in the sample. 



3 



