Document: DAV-3-53-6

Effects of grassland-invasive Juniperus virginiana on avian communities.

ENGLE, D.M.*, R.N.CHAPMAN, R.E.MASTERS and D.M.LESLIE, JR.

Oklahoma State University, Stillwater, OK 74078 USA ¹

Abstract:
Abundance of bird species associated with grasslands of the Southern Great Plains has declined while bird species associated with shrub and woodland habitats have increased in abundance. Recent exponential increases in the extent of fire-intolerant Juniperus virginiana may explain these trends in avian community composition within southern mixed prairies subject to J. virginiana invasion. The primary purpose of this study was to determine the effects of J. virginiana on compositional characteristics of local avian communities within mixed prairies of the Southern Great Plains. We censused birds and we measured J. virginiana canopy cover in 1998 and 1999 in grassland patches along three Breeding Bird Survey routes in northwest Oklahoma. We used ordination and regression to analyze composition of bird communities and to determine the effects of J. virginiana on avian habitat guilds and species of birds. A shift in bird community composition occurs at low cover of J. virginiana. Species associated with grassland habitats were negatively associated with J. virginiana cover and decreased in abundance as J. virginiana cover increased. Bird species associated with woodland and shrub habitats were positively associated with J. virginiana cover and increased in abundance with increasing J. virginiana cover. Conservation and recovery of declining grassland bird populations and maintenance of biological integrity of Great Plains grasslands will require efforts to control invasion of grassland habitats by J. virginiana.

Keywords: Grassland Birds, Great Plains Grasslands, Invasive Plants, Mixed Prairie

This abstract is being presented at: 10:30 AM in session:
AVIAN ECOLOGY