Dissertation/Thesis Abstract

Habitat and spatial ecology of the Western Screech-Owl ( Megascops kennicottii) in the Davis Mountains of West Texas
by Olivas, Corin Michelle, M.S., Sul Ross State University, 2015, 85; 1603804
Abstract (Summary)

Western Screech-Owls (Megascops kennicottii) are small, nocturnal owls that occur year-round throughout most of the Trans-Pecos region in West Texas, and are associated with deciduous woodlands and riparian habitats. Roadside nocturnal callback surveys, were established along well-defined trails within the Davis Mountains Preserve, and took place from May until August for two years to ascertain the relative abundance of Western Screech-Owls within the property. Abundance indices (birds detected/visit/station) were calculated for both survey seasons. Radiotelemetry was incorporated to determine certain life-history information, while habitat was characterized from both survey and telemetry sites. Occupancy models with detection probabilities were created using Program PRESENCE based on collected presence-absence data. Based on criteria for suitable screech-owl habitat previously defined in the literature, several models were also generated within ArcGIS to compare with the field data and to help predict areas of occupancy within the property. Owl abundance averaged 1.05 owls/point in 2013 and 0.82 owls/point in 2014. Six owls were marked during the study, and 3 of 6 locations were confirmed as daytime roosting sites. Statistically, there were no significant differences between occupied survey sites and telemetry sites, with only the percentage of canopy being significantly different with a mean difference of 9.32, t42 = -2.36, p = 0.023. Both owls and transmitters were discovered in dense juniper-oak mottes on north-facing slopes, indicating a preference for dense, short, closed canopy areas for roosting. Overall vegetative ground cover for the two seasons averaged 54% and 48%, respectively. It was concluded that none of the included covariates in the models influenced either occupancy or detection probabilities, though detectability demonstrated an overall trend based on time of night. GIS models did not reveal any variable that strongly influenced owl occupancy but did correspond with results from previous literature.

Indexing (document details)
Advisor: Ritzi, Christopher M.
Commitee: Kasner, Andrew C., Terry, Martin
School: Sul Ross State University
Department: Biology
School Location: United States -- Texas
Source: MAI 55/02M(E), Masters Abstracts International
Subjects: Wildlife Management, Ecology, Zoology
Keywords: Geographic information system, Megascops kennicottii, Point counts, Presence, Radiotelemetry, Texas, Western screech-owl
Publication Number: 1603804
ISBN: 978-1-339-23931-6
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