Breeding bird responses to juniper woodland expansion

Abstract

In recent times, pinyon (Pinus spp.)-juniper (Juniperus spp.) woodlands have expanded into large portions of the Southwest historically occupied by grassland vegetation. From 1997-1998, we studied responses of breeding birds to one-seed juniper (J. monosperma) woodland expansion at 2 grassland study areas in northern Arizona. We sampled breeding birds in 3 successional stages along a grassland-woodland gradient: un-invaded grassland, grassland undergoing early stages of juniper establishment, and developing woodland. Species composition varied greatly among successional stages and was most different between endpoints of the gradient. Ground-nesting grassland species predominated in uninvaded grassland but declined dramatically as tree density increased. Tree-and cavity-nesting species increased with tree density and were most abundant in developing woodland. Restoration of juniper-invaded grasslands will benefit grasslandobligate birds and other wildlife.

Avian Community Structure Along a Mountain Big Sagebrush Successional Gradient

“…In addition, bird species diversity (H 0 ) was positively correlated with PCD indicating an increase in avian diversity with an increase in structural complexity of vegetation. Similar to previous studies (Coppedge et al 2001, Rosenstock andvan Riper 2001), the dramatic increase in bird species diversity in shrub-steppe-juniper and old-growth juniper in contrast to the grassland and shrub-steppe states was associated with the additional vegetative layer provided by juniper trees. Maximum densities of 7 tree-nesting species in our study were in old-growth juniper, and 4 of 5 cavity-nesting species had higher densities in old-growth juniper than in shrubsteppe-juniper stands.…”

“…Shifts in the proportion of early and late-seral shrub-steppe communities and encroachment of juniper woodlands have likely resulted in significant changes in species composition, diversity, and abundance of breeding birds (Rosenstock and van Riper 2001). Most bird communities are influenced by changes in vegetative structure, and bird species diversity is often associated with increased structural complexity of plant communities (McArthur and McArthur 1961, Roth 1976, Cody 1981).…”

Northern Bobwhites and Postfire Succession

“…We used Tukey's Honestly Significant Difference multiple comparison procedure following a significant F-test (P , 0.05). Because time since fire varied among treatments, significance tests of a priori null hypotheses regarding differences in shrub attributes were likely to be false and uninformative ( Johnson 1999, Rosenstock andVan Ripper 2001). We compared brush density, canopy cover, and height using means and 95% confidence intervals (Johnson 1999).…”

Effects of conifer expansion on greater sage‐grouse nesting habitat selection

“…Soil water availability is also reduced in conifer-dominated landscapes (Roundy et al 2014, Kormos et al 2017, which may affect mesic riparian and meadow areas necessary for sage-grouse broodrearing (Atamian et al 2010, Donnelly et al 2016. Although some woodland guilds (e.g., tree and cavity nesters) of birds may benefit from conifer expansion, grassland and sagebrush obligates of high conservation concern decline with increasing conifer (Coppedge et al 2001, Rosenstock and Van Riper 2001, Reinkensmeyer et al 2007.…”