San Diego Natural History Museum--Your Nature Connection[San Diego County Bird Atlas Project]

WRENDERINGS
Notable Discoveries
Fall 1997

As participants begin sending in their forms, more interesting discoveries are surfacing.

The expanding Western Grebe continues to colonize new sites. Jim Determan found chicks riding atop their parents in San Dieguito Reservoir in square K8. The Eared Grebe, only an occasional breeder in San Diego County, was found summering at several sites too; no breeding confirmed, but probable at Lake Morena, where Richard and Susan Breisch saw a pair in T21 and Sue Smith saw courtship behavior and a possible juvenile in S21.

American Avocets, not known previously to nest inland in San Diego County, did so at two sites, the east end of Lake Hodges in square K11, where Ed Hall saw fledglings and juveniles, and at a pond on the Barona Indian Reservation in N14, where Phil Pryde found a pair incubating.

The nonnative Spotted Dove, thought possibly to have died out of at least southern San Diego County, may be hanging on by a slender thread in S11, Encanto: Phil Unitt saw a single singing male along Radio Road just east of 60th Street. This was his first observation of the species in San Diego County in 12 years.

The Warbling Vireo is now a very rare breeding species in San Diego County. Though it once nested more commonly, brood-parasitism by Brown-headed Cowbirds decimated it. Widespread trapping of cowbirds may give it a chance to recover somewhat. Atlas participants have reported so far three observations of Warbling Vireos from mid-June onward: Lee Taylor had two territorial birds on 14 June in K9, Elfin Forest, Lori Hargrove had two singing males on 15 June in R23, Kitchen Creek, and Paul Jorgensen had two on 6 July in C1, San Mateo Point. Since migrants heading farther north pass through regularly until early June, observations earlier in the spring can be difficult to interpret.

Western Bluebirds have been seen nesting at several sites unexpectedly close to the coast. Mona Baumgartel had them on the golf course in J7, La Costa, Jim Determan had them nesting in a hole in a eucalyptus in K8, Olivenhain, Andy Mauro had them nesting in L8, Rancho Santa Fe, and, most surprisingly, Jim Wilson had a pair raise two fledglings in R9 along the San Diego River behind the Fashion Valley shopping center, in spite of the major construction nearby.

Along San Mateo Creek just above Interstate 5 in C1, Lisa Ellis and Mike LeBuffe found two to four territorial Swainson's Thrushes, a new site for this species very sparse here at the southern edge of its breeding range in San Diego County (migrants from farther north, of course, are seen commonly).

Just the fourth observation of a summering, singing Hermit Thrush in San Diego County was made on Palomar Mountain in E14, Boucher Hill, by Chuck Handel on 25 June. Bob Turner and Karen Messer found it still at the same site two days later, noting it as paler than the Hermit Thrushes we see commonly in the winter. Presumably it is the subspecies sequoiensis, breeding in the Sierra Nevada and San Bernardino Mountains, paler and more lightly spotted than the three subspecies from Alaska and British Columbia that winter in southern California.

Of all the breeding birds of San Diego County, LeConte's Thrasher has one of the sparsest populations and is one of the most difficult to find. In addition to the regular site in E26, Clark Valley SW, where Ed Post and Mary Beth Stowe found a pair with a fledgling, the species was found at two additional sites. Ginger Rebstock and Karin Forney found three, including a pair, in G29, Five Palms Spring; one was found in P27, Egg Mountain, on a San Diego Audubon Society field trip to Bow Willow Canyon--thanks to David Seay for the record.

Two new sites for the endangered San Diego Cactus Wren have come to light this year: Geoff Rogers found two singing males in the upper end of Oak Canyon in O11, Miramar East, and Phil Unitt found three individuals, including a pair, just northeast of the Malcolm X Library (corner of Euclid and Market streets) in S11, Encanto.

The Blue-gray Gnatcatcher, thought to be practically extirpated as a breeding species from San Diego County's coastal lowland by cowbird parasitism, was recently rediscovered nesting in numbers in Miramar Naval Air Station by Bill Haas. Now Geoff Rogers gives us the first documentation of how numerous the species is there: 13 nests just in square O11, Miramar East!

Dick Barber and Clark Mahrdt found Dark-eyed Juncos continuing to summer at an atypically low elevation (1200-1300 feet) in Boden Canyon in squares I14 and J14; Clark first found them nesting there a few years previously.

One of the least expected observations generated by the atlas effort so far has been Paul Jorgensen's sighting of a singing Nashville Warbler at the weir at the end of Doane Valley Trail (downstream from Doane Pond) on Palomar Mountain in D14, French Valley. This is the first summer report in San Diego County of the Nashville Warbler, a species with a breeding range extending south normally only to the San Bernardino Mountains--and rare even there. The bird sang nearly constantly for a half hour when discovered on 24 June but couldn't be found on a follow-up visit.

Paul's follow-up visit, however, revealed a pair of Wilson's Warblers at the same site, quite a discovery in itself. Though common in migration, Wilson's Warbler was never a common breeding species in San Diego County. Then with the onslaught of Brown-headed Cowbirds earlier this century, the range retracted north. This is only about the fourth report of summering Wilson's Warblers in the county in the past 25 years. Fall migrants had begun arriving by 8 August.

The Black-throated Gray Warbler is a very rare breeding bird in San Diego County, nesting only in the highest mountains. The only square in which a breeding Black-throated Gray has been reported so far is D15, Palomar Observatory, where Ken Weaver and Dennis Huckaby found a female feeding a fledgling on 30 July.

Intriguing were two reports from the Anza-Borrego Desert of the Summer Tanager, a species that has never been known to nest in San Diego County--but could, as it does at some other desert oases. Ginger Rebstock and Karin Forney found one or two males on 3 May in G29, Five Palms Spring, and Lori Hargrove found one on 6 July at "fourth grove" in Borrego Palm Canyon, F23.

Two Harris' Hawks continue to be seen in G24, Borrego Springs S. On 22 July, Mark Jorgensen spotted them one-half mile south of Palm Canyon Drive along Borrego Valley Road.

Even though our first season focused on breeding birds, our efforts revealed some rare migrants, too. Leftover from last winter's invasion of montane species were Evening Grosbeaks--a pair videotaped by Joe and Mary Ann Robinson on 15 April in E15, Mendenhall Valley, and a single female seen by Robb Hamilton on 15 May in O22, Noble Canyon--and Cassin's Finches--two seen by Jim Wilson and Mike McNew in P21, Pine Valley.

Participants in the Anza-Borrego Desert found a couple of rare migrant warblers: a Virginia's on 4 April in H25, Casa del Zorro, by Herb Young and Mary Mosher, and a Black-and-white on 23 April in I24, Tamarisk Grove, by Phil Nelson.

A couple of spring vagrants encountered by Phil Unitt and Jack Schlotte: a male Rose-breasted Grosbeak in O22, Noble Canyon, on 8 June, and a male Indigo Bunting in S11, Encanto, on 21 June.

Any report on San Diego County birds over the summer wouldn't be complete without mention of the Belcher's or Band-tailed Gull found at the Tijuana River mouth on 3 August found by visitors Doug Shaw and Bob Brandiff and seen by many others at least through the 23rd. This native of the Humboldt Current along the west coast of South America is poorly or not illustrated in most guides, so its identification was a challenge. But it was easily picked out as different by its mottled gray hood, whitish collar, very dark gray back, and mostly black tail. The bill was perhaps the bird's most striking feature, yellow with a black subterminal ring and bright red tip. Did this nonmigratory species make it to San Diego on a ship, or was it driven out of its normal range by a looming El Niño? It has been reported previously from Texas and Florida but never from California. We'll never know its origin for sure.

birdatlas@sdnhm.org

Fall 1997 Wrenderings | Wrenderings Archive | Bird Atlas Introduction