REP50664

• Permit No: M1993041
• IBM Index Class Name: Report
• Doc Name: BURROWING OWL SURVEY OF DOWE FLATS PROJECT AREA BOULDER CNTY COLO
• Media Type: D
• Archive: No

Burrowing Owl Survey Dowe Flats Project
1
' 1.0 INTRODUCTION
Burrowing owls (Athene cunicularia) are a species of high federal
interest, a Colorado "Species of Special Concern" (Webb 1985), and
a species that has been declining in Boulder County (Hallock 1993).
' Hallock (1993) reported only one known nest site in Boulder County
in the last three years. Although these owls have never been
reported from Dowe Flats, the area represents apparently suitable
burrowing owl habitat. At the request of Boulder County, surveys
for burrowing owls were conducted throughout Dowe Flats in 1993, as
part of the wildlife baseline studies for Southwestern Portland
Cement Company's {Southdown, Inc. 1993) proposed limestone mine.
' This report summarizes the results of those surveys.
2.0 METHODS
' Three replicated surveys of suitable burrowing owl habitats, within
and beyond the Dowe Flats project area, were conducted on May 22,
' July 24, and August 27, 1993. The first survey was conducted at an
appropriate time of year to identify owl presence prior to any
nesting failure and potential departure of the adults. The second
and third surveys were conducted when fledglings would be above
' ground flying.
During the May survey, black-tailed prairie dog (Cynomys
' ludovicianus) distribution in the valley was mapped to (1)
determine the distribution of potential burrowing owl habitat, (2)
to document and quantify the expanded distribution from that
' documented by HRM (1987), and (3) to facilitate upcoming (winter
1993/ 94) black-footed ferret (MUSte1a nigripes) surveys (Map 6,
back pocket). Late May was an excellent time of year to map
prairie dog distribution as young-of-the-year were above ground,
' facilitating the identification of occupied areas.
The study area surveyed for owls extended beyond Southwestern's
' proposed Dowe Flats project area (Southdown, Inc. 1993). The
survey area extended east up the sides of Rabbit Mountain, from
near its southern tip, north past the County parking lot, north to
the Syntex site, west onto the slopes of Indian Mountain (west of
' the Northern Colorado Water Conservancy District canal), and south
beyond the most northern irrigation ditch.
' Each owl survey systematically covered the mapped prairie dog
distribution (Map 1) and suitable adjacent habitats in search of
owls using a 15-45x spotting scope and binoculars. Surveys were
' conducted from a vehicle along local roads and by walking to
vantage points and searching a given habitat block before moving to
search the next habitat block. Approximately 90% of the study area
Western Ecosystems, Inc. September 1993