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

WRENDERINGS
Bird Atlas News and Updates
Fall 2000

The Blockbuster to End All Blockbusters
WingDing Things
Expedition to Guadalupe Island
Construction at the Museum
Coming up at the Museum...


The Blockbuster to End All Blockbusters

Our double-header blockbuster in the Lake Henshaw region, 17-18 and 24-25 June, succeeded beyond my wildest expectations. As a result of the event, we cleared the threshold in three squares (F17, F19, and G19) and are short just a few hours (all criteria with respect to the target list met) in four others (E18, F18, G17, and G18). The weekends generated so many interesting discoveries that they merit a "notable observations" column all their own.

[Sketch by Sue Smith indicating the markings and features of a Swainson's Hawk.]The most remarkable discovery was so far "outside the box" that I wasn't prepared to accept the evidence our observers were reporting. There had been no local summer records of the Swainson's Hawk since the breeding population died out in 1935. So when Sue Smith and Kirsten Winter reported a flock of eight hawks with some features of Swainson's north of Lake Henshaw (F17) on 17 June I assured them they must be molting one-year-old Red-tails. Even the following weekend, when Ginger Rebstock and Joe Barth went to the same area, saw 25, and returned squirming over how much the birds resembled Swainson's Hawks, I didn't consider this plausible. Finally, Jim Pike, an excellent birder from Orange County, passed through the same area the same weekend totally independently and reported Swainson's Hawks. The evidence of three independent sources finally penetrated my skull. The one thing I got right was that the birds were molting one-year-olds. Apparently, being too young to breed, they had no need to return to their natal region. When the flock encountered the millions of grasshoppers in the Henshaw basin on their spring migration they stayed to feast. Sue's sketch and notes are a great example of how to support an identification of a rare bird.

Likewise, no summer records of the Bald Eagle have been published from San Diego County. So it was quite a shock when I encountered an adult on the north side of Lake Henshaw (G17) on 18 June (less difficult to confuse than Swainson's Hawk). Remarkably, Dave Bittner reported another adult Bald Eagle (the same individual?) at Lake Cuyamaca (M20) two days later. Yet another good bird of prey was the Zone-tailed Hawk seen in Warner Valley (G19) by Ed Hall and Andy Mauro on 24 June, just a few miles from the nest site of a few years ago on Hot Springs Mountain.

Claude Edwards and David Seay found an American Wigeon and a Blue-winged Teal, both very rare in summer, at Swan Lake (F18) 24 June. Another unexpected prize was the pair of Vermilion Flycatchers found by James Barr and Joe Barth near the old Warner Ranch (G19) on 17 June. Andy Mauro and Ed Hall followed up a week later by finding their nest, just the third confirmed nesting site for the Vermilion Flycatcher in the past four years, and first on the coastal slope. See "Focus On" in this issue for the new Tricolored Blackbird colonies, including one of the largest in San Diego County, brought to light by these blockbusters.

Thanks very much to Bill Haas for hosting us overnight at his new home just downstream of Lake Henshaw along the San Luis Rey River (F16). This, of course, is also a great birding spot. Besides being at the center of California's biggest colony of the Willow Flycatcher, this area was home to nesting Black-throated Gray Warblers for a second year. The latter is rarely found nesting in San Diego County and otherwise only at high elevations. A pair brought their fledgling through the oaks around Bill's home 24 June to be seen by all of us staying over there during the second blockbuster.

Thanks to Paul Dorey of Vista Irrigation District for authorizing our access to the district's lands for these weekends and to Claude Edwards for making the arrangements.


WingDing Things

It's time for another WingDing! As promised in the last issue of Wrenderings, this will be an informal outdoor event in the beautiful Laguna Mountains on Saturday 16 September. Kirsten Winter of the U. S. Forest Service has reserved the entire group camp at Horse Heaven, giving us plenty of room to socialize and enjoy the mountains. Be sure to bring your binoculars and hiking boots, or your favorite comfortable folding chair if you prefer. We'll gather in the Buttercup Loop picnic area around noon for a delicious lunch prepared by PHAT Bar-B-Que, so do your hiking early and come with an appetite! After lunch Phil will give an update on the project and we'll recognize and award our participants who have reached the breeding threshold goals for their squares this year.

You should already have received your invitation in the mail, with a map and more details. Please call 619-232-3821 ext. 235 or send e-mail to Aklovstad@sdnhm.org by Monday 11 September to let us know if you will be joining us and how many guests you will be bringing so that we can plan accordingly.

Many thanks to Kirsten for helping with the arrangements for what promises to be another great event! Hope to see you there!


Expedition to Guadalupe Island

As you may have read in Scientific American or seen on the museum's website, the San Diego Natural History Museum mounted an interdisciplinary binational expedition to Guadalupe Island, 300 miles south of San Diego, in early June. We observed and quantified the island's continuing degradation through overgrazing by naturalized goats. The island's birds are struggling too-we confirmed that the Red-breasted Nuthatch and Ruby-crowned Kinglet, formerly resident on the island, are now extirpated, and the major colonies of Xantus' Murrelet and Leach's Storm-Petrel were reproducing poorly. The endemic subspecies (or species?) of the House Finch, Rock Wren, and junco are still reproducing vigorously, but the last may be dependent on the shrinking grove of cypress trees. The one item of good news is that the Laysan Albatross colony has relocated from the main island, where it was subject to attacks by feral dogs, to two of the offshore islets, where the only predators are Burrowing Owls. We hope our expedition will stimulate the removal of the goats and initiate the island's recovery.


Construction at the Museum

Construction will restrict access to the bird collections increasingly over the next few months. Already the waterfowl skeletons and skins of most large water birds are blocked. The entire collection will be inaccessible for the first half of 2001 while the department is being renovated. So if you're thinking of using the bird collection, call for an appointment sooner rather than later! Thanks for your understanding, and thanks for your support as we look forward toward a newly renovated department of birds and mammals in the fall of 2001.


Coming up at the Museum...

Laguna Hanson with Tom Oberbauer and Mike Evans, overnight trip to a unique natural lake in the Sierra Juárez of northern Baja California. Saturday 23 September, 7 AM, to Sunday 24 September, 5 PM. Museum members $115, nonmembers $135. Limited carpool space available for an additional $75 per person.

Birding by Sound with Claude Edwards, with field trips to Lindo Lake and Santee Lakes. Class Wednesday 18 October, 7-8:30 PM; field trip Saturday 21 October, 9-11:30 AM. Museum members $21, nonmembers $29.

Birding and Geological Exploration at the Salton Sea with Don Albright and Bob Miller. Saturday 4 November, 7:30 AM-7:30 PM. Price includes van transportation from San Diego. Museum members $59, nonmembers $69.

What Bird Was That? Winter birding with Claude Edwards. Class Wednesday 13 December, 7-9 PM; field trip Saturday 16 December, 8 AM-3 PM. Museum members $21, nonmembers $29.

For more information, to register, or to become a museum member please call 619-232-3821 ext. 203, or see the online version of the Museum's Education Brochure.

Swainson's Hawk sketch by Sue Smith

birdatlas@sdnhm.org