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White-breasted nuthatch density and nesting ecology in oak woodlands of the Willamette Valley, Oregon

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dc.contributor Schmitz, Richard A.
dc.contributor Robinson, W. Douglas
dc.contributor Gitelman, Alix
dc.contributor Brooks, Raymond
dc.date 2006-01-30T16:38:18Z
dc.date 2006-01-30T16:38:18Z
dc.date 2005-12-13
dc.date 2006-01-30T16:38:18Z
dc.date.accessioned 2013-10-16T07:29:49Z
dc.date.available 2013-10-16T07:29:49Z
dc.date.issued 2013-10-16
dc.identifier http://hdl.handle.net/1957/890
dc.identifier.uri http://koha.mediu.edu.my:8181/xmlui/handle/1957/890
dc.description Graduation date: 2006
dc.description Habitat loss causes a reduction in available resources for wildlife, alters the configuration of remaining habitat, and may isolate wildlife populations. White-breasted nuthatches (Sitta carolinensis) are experiencing long-term population declines in the Willamette Valley of Oregon, where they are historically associated with oak woodlands. As secondary cavity-nesters, white-breasted nuthatches may be limited by the availability of existing cavities for nesting and roosting. Oak vegetation in the Willamette Valley has changed since European-American settlement times from vast areas of open oak savanna to isolated closed-canopy stands separated by agricultural fields. We examined nuthatch density, nest cavity selection, and nest success in relation to oak woodland structure and landscape context. We conducted point transect surveys in 3 strata: woodland interiors, large woodland edges, and small woodlands. We located and monitored nuthatch nests and sampled vegetation at nest locations and matching random locations around each nest. Woodland structure and edge density were measured at a 178-m radius (home range) scale, and landscape context was measured using vegetation cover within a 1-km radius around point transects and nests. We used program DISTANCE to fit detection functions and calculate nuthatch densities. We used conditional logistic regression to compare nest locations with random locations, and analyzed nest success with Mayfield logistic regression. White-breasted nuthatch density was significantly higher in small woodlands than in edges of large woodlands, which had higher nuthatch density than woodland interiors. Density of nuthatches increased with a combination of oak cover within a 1-km radius of the point, edge density within a 178-m radius, and number of oak trees >50 cm diameter at breast height (dbh) within a 100-m radius. Nest cavities were situated in oak trees containing more cavities than random oak trees that had cavities, and oak trees used as nest trees had a larger dbh than oak trees within random plots. Local woodland structure at nest locations was characterized by larger trees, measured by greater mean dbh, canopy cover, and basal area of oaks than random locations within the home range. Nest success in natural cavities was 71% and was not predicted by attributes of nest cavities, nest trees, local woodland structure at nests, woodland structure at the home range scale, or landscape context. These results suggest that the most suitable habitat for white-breasted nuthatches in the Willamette Valley includes oak woodlands in close proximity to one another with a high proportion of edge and mature oak trees. Managers should preserve trees containing cavities and large oak trees whenever possible. Thinning of small oaks and removal of conifers in oak woodlands to create more open, savanna-like conditions may also promote the development of larger oaks with more spreading branches, providing more opportunities for cavities to form and more foraging surface area for nuthatches.
dc.language en_US
dc.subject White-breasted nuthatch
dc.subject Sitta carolinensis
dc.subject Nest success
dc.subject Program DISTANCE
dc.subject Distance sampling
dc.subject Willamette Valley
dc.subject Oregon white oak
dc.subject Quercus garryana
dc.subject Oak woodlands
dc.subject Edge
dc.subject Woodland interior
dc.subject Oak savanna
dc.subject cavity-nesting
dc.subject nest cavity selection
dc.subject density
dc.subject point transects
dc.subject conditional logistic regression
dc.subject Mayfield logistic regression
dc.subject Landscape context
dc.subject Woodland structure
dc.subject Isolation
dc.title White-breasted nuthatch density and nesting ecology in oak woodlands of the Willamette Valley, Oregon
dc.type Thesis

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