Volume 11, No. 2

JONATHAN L. ATWOOD (Author)

THE UNITED STATES DISTRIBUTION OF THE CALIFORNIA BLACK-TAILED GNATCATCHER

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The Black-tailed Gnatcatcher, Polioptila melanura, is represented in California by two subspecies: P. m. lucida and P. m. californica (AOU 1957). These forms were originally described as distinct species on the basis of plumage differentiation, with californica having darker underparts and less white on the underside of the rectrices than lucida (Figure 1).

Later, Grinnell (1926) concluded that individual variation exhibited by the central Baja California race pontilis and the Cape San Lucas form margaritae suggested that californica and lucida were merely the extremes in a continuous series of subspecies. However, there do not appear to be any documented localities of overlap or genetic introgression between lucida and the californica/pontilis/margaritae group (Grinnell 1928, Grinnell and Miller 1944).

Therefore, rather than indicating genetic interchange between the populations, the resemblance of margaritae to the similarly pale lucida could be interpreted as convergence resulting from a north–south cline of dark to light plumaged birds within the californica group. Also, since Grinnell's taxonomic revision was based on morphological characters and apparently failed to consider the possible significance of relatively pronounced vocalization differences between lucidaand californica, additional investigation of speciation in the Black-tailed Gnatcatcher complex is currently being conducted.

BRUCE G. MARCOT, JEFFREY GARDETTO (Author)

STATUS OF THE SPOTTED OWL IN SIX RIVERS NATIONAL FOREST, CALIFORNIA

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Knowledge of the distribution and status of the Northern Spotted Owl (Strix occidentalis caurina) in northwestern California is incomplete. Gould (1974) surveyed the North Coast region and recorded 41 pairs in four counties, 6 pairs of which were found on the Six Rivers National Forest. Recent updates to Gould's surveys (Gould 1977, 1978) added 35 pairs to the four-county list, and other records (Six Rivers National Forest files) of unverified sightings added 14 more, for a total of 90 pairs. Gould (1977) reported a statewide total of 191 Northern Spotted Owls, representing 122 pairs.

The present study was prompted by a need for more intensive and local surveys on the Six Rivers National Forest. The goals of our research were to:

• Survey 25 potential timber sale areas for presence of Spotted Owl breeding territories

• Assess ecological distribution of Spotted Owls

• Develop preliminary guidelines for management and future research on Spotted Owls on the Six Rivers National Forest

WILLIAM C. SHUSTER (Author)

NORTHERN GOSHAWK NEST SITE REQUIREMENTS IN THE COLORADO ROCKIES

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This paper deals with 20 Northern Goshawk (Accipiter gentilis) nest sites I studied in northern Colorado. Numerous references have described typical Goshawk nests (Bailey and Niedrach 1965; Bent 1937; Beebe and Webster 1964; Brown and Amadon 1969), but there are few detailed studies of their nest sites. Bartelt (1977) completed a study in South Dakota using data-gathering methods similar to this paper. Also, Reynolds (1971) and Reynolds and Wight (1978) described habitat requirements in Oregon.

For the purpose of this paper, a nest site is defined as the area immediately surrounding the nest in which most of the birds’ nesting activities occur. In most cases, this is confined to a definite size and age timber stand

JOHN R. ARNOLD (Author)

DISTRIBUTION OF THE MOCKINGBIRD IN CALIFORNIA

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Several authors have commented on the expanding range of the Mockingbird (Mimus polyglottos) in California (Seymour 1978; Legg 1959). Grinnell (1911) first reported an expanding population of the Mockingbird in California, followed by my paper 23 years later (Arnold 1935). The present paper reports continuing range expansion and speculates on the factors influencing this expansion.

Figure 1 shows the approximate range of the Mockingbird in California in 1978. This map does not indicate the many scattered fall and winter records.

JOSEPH R. JEHL (Author)

TRENDS IN THE STATE LIST OF CALIFORNIA BIRDS

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It is hardly surprising that California—with its large size, seacoasts, and varied topography—would harbor one of the most diverse assemblages of birdlife of any state. The number of species recorded within its boundaries is exceeded only by that of Texas—and the difference is small. Grinnell and Miller (1944) recognized 427 species as having occurred naturally. Adjusted for the inclusion of introduced species, shifts in taxonomic concepts (AOU 1957, 1973, 1976), and critical reexamination of some early records (McCaskie et al. 1970), the 1944 list contains 431 species.

In the subsequent 3½ decades, the state list has continued to increase at an astonishing rate, and by the end of 1979 stood at approximately 535 species, a 24% increase.

Species recorded in the state for the first time since 1944 are listed in Table 1. In Table 2, I have divided this time period into several intervals and attempted to discern the probable source area for each of the additions: North American, Mexican, Arctic/Asian, or Pelagic. These categories are broad and occasionally overlap

DIRK VAN VUREN (Author)

A HARRIS' HAWK IN UTAH

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The distribution of the Harris' Hawk (Parabuteo unicinctus) in the United States is limited to the southern regions of California, Arizona, New Mexico, and Texas, with occasional records as far north and east as Ohio and Louisiana (AOU Check-list, 1957).

With the exception of three sightings in the Colorado River Valley in the southernmost part of Nevada (Linsdale, Condor53:228–249, 1951; Johnson, Condor 58:449–452, 1956; Lawson, Western Birds 8:73–90, 1977), and one sighting in southwestern Utah (Behle and Perry, Utah Birds, Utah Museum of Natural History, Salt Lake City, 1975:14), the Harris' Hawk has not been reported north of the western part of its range. This paper reports a second sighting of a Harris' Hawk in southern Utah.

Martin Bray, Gordon Hildebrant, and I independently identified an adult Harris' Hawk on five occasions between 1 August and 9 September 1978 in the Henry Mountains, Garfield County, Utah, 35 km south of Hanksville.

 

LAWRENCE J. BLUS, CHARLES J. HENNY (Author)

CANADA GEESE INCUBATE EGGS LAID IN PREVIOUS YEARS

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In 1978, we initiated a study of the effects of heptachlor-treated cereal grains on wildlife—particularly the Canada Goose (Branta canadensis)—in the Columbia Basin (Blus et al. in Jarvis and Bartonek, Management and Biology of Pacific Flyway Geese, OSU Book Stores, Corvallis, OR, 1979: 105–116).

To assess the impact of heptachlor and other pollutants on the reproductive success of Great Basin Canada Geese (B. c. moffitti), we collected a sample egg for pesticide analysis from each of 41 marked nests on the Umatilla National Wildlife Refuge in Oregon and Washington, and another series about 65 km upstream from Umatilla on the McNary Recreation Area, Washington. In these two arid areas, geese nest on islands in the Columbia River.

Sample eggs collected from three active nests in mid-March were addled, and the contents were gray. We judged that these three eggs were laid during a previous year, since geese in this area initiate laying in early March, and two of the three nests contained unincubated, incomplete clutches that were ultimately completed and incubated.