Aspen Bibliography


Nest site relationships among cavity-nesting birds of riparian and snowpocket aspen woodlands in the northwestern Great Basin

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Weexaminednest-siteandnest-cavitycharacteristicsforsixspeciesofcavity- nestingbirds in montane riparian and snowpocketaspen(Populustremuloides)woodlan& in the northwestern Great Basin. Live trees and snagswith DBH >24 cm were favored as nestsitesbyall species.Red-napedSapsuckers(Sphy;apicusnuchalis)andNorthern Flickers (Colaptesauratus)provided different sizesofnest cavitiesfor a suiteof nonexcavatorspecies. Flickers preferentially nested in snags;sapsuckersnested primarily in live trees, but used live treesand snagsin proportion to their availabilities. Relative abundancesof excavators and nonexcavatorswere associatedpositively with numbers of cavities. Nest-site variables o v e r l a p p e d e x t e n s i v e l y a m o n g s p e c i e s ;T r e e S w a l l o w s ( T a c h y c i n e t a b i c o l o r ) r e l i e d h e a v i l y o n s a p s u c k e r sf o r p r o v i s i o n o f n e s t c a v i t i e s , E u r o p e a n S t a r l i n g s ( S t u r n u s v u l g a r i s ) a n d Mountain Bluebirds(Sialia currucoidesp)rimarily usedflicker-excavatedcavities,andHouse Wrens (Troglodytesaedon) used nest cavities acrossthe broadest range of nest-site char- acteristics.Compassorientation of nest-cavity entranceswas stronglybimodal, with most facingeastor southwest.Cavity entrancesof speciesthat foragedlargelyoutsideof riparian woodlandswereorientedtowardwoodlandedge,in contrasttonestcavitiesusedbyspecies that foragedlargelywithin riparian woodlands.Snowpocketwoodlandswere much more extensivethan riparian aspen,but birds stronglypreferredriparian aspenstandsasnesting habitats,presumablydue to the scarcityof largeaspenin snowpockets.Nest cavitiesappear to be a limiting resourcewith high potential for interspecificnest-sitecompetition in these woodlands.Decadesof livestock overuseand fire suppressionhave greatlydiminished the availability of largeaspenin riparian habitatsthroughoutthe region.