Breeding Birds in Riparian and Upland Dry Forests of the Cascade Range

Abstract

We quantified breeding bird abundance, diversity, and indicator species in riparian and upland dry forests along 6 third‐ to fourth‐order streams on the east slope of the Cascade Range, Washington, USA. Upland dry forest on southerly aspects was dominated by open ponderosa pine (Pinus ponderosa) and dry Douglas‐fir (Pseudotsuga menziesii) plant associations. Upland mesic forest on northerly aspects was dominated by closed‐canopy Douglas‐fir or dry grand fir (Abies grandis) plant associations. Riparian overstory vegetation was dominated by black cottonwood (Populus trichocarpa) plant associations with a prominent hardwood tree and shrub component. We quantified bird assemblages, diversity, and abundance from parallel point transects on riparian and adjacent dry and mesic upslope forests. We detected 80 bird species from >12,000 point‐transect observations during 1998–1999. Eighteen species accounted for 75% of all detections. Species richness and evenness were similar in all 3 forest types, with approximately 35 species and high evenness (0.85) in each forest type. Bird species assemblages differed among dry, mesic, and riparian forest types, with the greatest differences between riparian and both dry and mesic upland forests. Riparian forest had the greatest number (9) of strong characteristic, or indictor, species among the 3 forest types. Upland mesic forest was characterized by 7 indicator species. Upland dry forest had 4 indicator species. Our results indicate that current standards and guidelines for riparian buffers zones would allow for avian refuge and corridor functions along these streams. Forest managers could use our indicator species to predict and monitor shifts in upland forest species composition from thinning and prescribed burning practices that are used to reduce fuels in uplands and to reduce continuity of fire effects between riparian and upland zones.

Can severely fragmented patches of riparian vegetation still be important for arid-land bird diversity?

“…Habitat characteristics that pre-dispose riparian vegetation to supporting unique avian assemblages in southern Africa (Monadjem, 2003, this study) and elsewhere (e.g. Lehmkuhl et al, 2007), include the relative complexity of vegetation structure, particularly in arid regions (Gregory et al, 1991), and greater productivity, owing to greater soil moisture and nutrient availability (Naiman and Dé camps, 1997). Fleishman et al (2003) found that while species richness was determined by habitat structure (physiognomy), avian species composition was determined more by habitat species composition (floristics).…”

Effects of proximity to riparian zones on avian species richness and abundance in montane aspen woodlands

“…Many studies have revealed greater bird species diversity and abundance in riparian zones than in surrounding habitats, but this pattern is most prominent in arid regions Jakle 1985, Woinarski et al 2000). In mesic regions, the association is often weak or nonexistent (McGarigal and McComb 1992, Pearson and Manuwal 2001, Loehle et al 2005, Lehmkuhl et al 2007), especially where the transition between riparian and upland vegetation is indistinct (Wiebe andMartin 1998, Shirley 2005). Few investigators have examined the extent to which positive effects of riparian zones on bird species richness and abundance might extend into adjoining habitats.…”

“…, Lehmkuhl et al. ), especially where the transition between riparian and upland vegetation is indistinct (Wiebe and Martin , Shirley ). Few investigators have examined the extent to which positive effects of riparian zones on bird species richness and abundance might extend into adjoining habitats.…”

Effects of fuel reduction on bird density and reproductive success in riparian areas of mixed-conifer forest in southwest Oregon

“…Other species did not differ by treatment year, suggesting either density was not affected by thin and handpile treatments nor prescribed burning, that the affect of treatments was consistent in buffered and unbuffered streams, or that the affect of a buffer was overshadowed by an upland treatment effect. The latter may be the case because areas of mid-elevation streams can have similar vegetation composition and structure as the upland and exhibit similar species composition (Finch, 1989;Knopf and Samson, 1994;Lehmkuhl et al, 2007). Seavy and Alexander (2006) found that prescribed fire in mixed-conifer/hardwood habitats had minimal effect on shrub and canopy cover and little effect on bird abundance.…”