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Lorenciro Canyan Mine -Wildlife rerhnicaf Report • The diurnal surveys were conducted in conjunction with other field procedures. Generally, potential breeding territories were identified from repeated observations of birds in a specific area. Once a potential territory was identified, attempts were made to locate a nest. If a nest was located, it was monitored through the breeding season. Attempts to locate nests included ground and aerial checks. Nests were field checked for activity in May 1996. The auditory census involved driving areas of potential habitat after dark and playing taped calls of owls potentially occurring in the area. The auditory census was conducted in May 1996. Stops for tape playback were at approximately 400-m (0.25 mile). Playback of calls progressed from the smallest owls to the largest. This order was used to avoid alarming the smaller owls. Areas were owls responded were recorded on project base maps. Breeding Bird Survey Birds other than raptors within the permit area were sampled using a line transect method. This method was selected over the more commonly used strip transect sampling method (i.e. Emlen transects) for three reasons. First, line transect sampling has a sound theoretical framework involving rigorously-developed, well-founded estimation methods (Burnham et al., 1980). Most other estimation methods are ad hoc approaches developed with no theoretical basis (Burnham et al., 1981). • Secondly, many factors of concern in most strip transect approaches can be safely ignored during analysis of line transect data if a suitably "robust" estimation procedure is used (Burnham et al., 1981). These factors include things that influence the detection of birds. Weather, habitat, bird species, and observer differences are examples most commonly cited in the literature. Consequently, no adjustments, such as coefficients of delectability, are necessary. Third, all birds away from the centerline do not have to be detected to provide valid estimates. Even if a substantial fraction of the birds go undetected, a properly conducted line transect survey will provide valid estimates of density (Burnham et al., 1981). In contrast, a fundamental assumption of strip transect sampling is that all birds within the strip will be detected. A total of five transects were established in four major habitat types. Transects were established in the following types: grassland (1), oak pinyon (1), and conifer forest (3). Blocks of habitat within accessible areas that could accommodate minimum transect lengths of 800 m (2640-feet) were randomly selected. Transects were laid out using a compass and tape measure. Each transect was marked at 20-m (66-foot) intervals to facilitate location of birds in relation to the transect. Transects were all conducted in the same manner. Each transect was walked at approximately 1 km/hr (0.6 mph). Observed birds were located, identified to the extent possible, and the perpendicular distance from the transect to the birds initial location estimated to the nearest meter. Wildlife 675/December 9, 1996 4