from the Field
Bird Atlas Trivia
With nearly all the breeding-season data entered now, we can step back and look at some of the general patterns in our bird atlas results. I've gained enough experience with the database-management program that I can assemble some of the complex multistep queries necessary for asking some of these questions. Questions like "what is the most widespread breeding species in San Diego County?" or "what square has the most breeding species?" may seem like bird atlas trivia, but they are the first step in analyzing our results, besides being good clean fun.
What is the most common breeding bird in San Diego County? The House Finch takes this prize by a long shot. Simply adding all the House Finches reported on daily field forms yields over 96,000, over 40% greater than the species in second place, the Cliff Swallow. The House Finch is also far in the lead for number of breeding confirmations, with 25% more than the species in second place, the Bushtit. The House Finch, Bushtit, and European Starling are the three species with over 1000 confirmations each so far.
What is the most widespread breeding bird in San Diego County? Reckoned from the number of squares where reported as at least possibly breeding, the Mourning Dove edges into first place, with 476 of 479 squares. The House Finch and Common Raven are tied for second place at 475 each. Only these three species can claim to be distributed as breeding species over the entirety of San Diego Countyand thus reveal the broadest tolerance of diverse environmental conditions.
What is the square with the most possibly breeding species? This is a slippery question because applying a uniform standard for each species over all squares requires a lot of judgment. I have tried to be conservative but reasonable. I do not think many if any waterbird colonies have escaped us, so I have designated colonial waterbirds as in suitable habitat only in squares where actual nesting colonies have been located. Many summer visitors like the Western Wood Pewee and Warbling Vireo are more widespread as migrants than as breeding species, requiring comparison of dates of observations against the species' migration schedule. Large birds of prey may forage in areas outside the squares where they nest. After all these complications are taken into account, the squares with the greatest diversity of breeding birds are E6, O'Neill Lake, in Camp Pendleton, and K11, Kit Carson Park, which includes the upper end of Lake Hodges (at high water). These two squares are tied at 101 species each, the only two squares with over 100 possibly breeding species. Both have extensive aquatic and riparian habitats. The significance of the Lake Hodges area to birds has already been recognized in its designation as an "important bird area." Both squares benefited from intense coverage by two of our most dedicated and skilled participants, Pete Ginsburg and Ed Hall.
What is the square with the fewest breeding species? With at most 14 possibly breeding species and only 6 confirmed species it is H29, Squaw Peak, which lies entirely within the Ocotillo Wells State Vehicular Recreation Area. Even the Red-tailed Hawk and Common Raven, included in the 14, may have been visitors from adjacent squares where they have been confirmed, and the suitability of the area for the single pair of Ash-throated Flycatchers observed may hinge on whether that species can nest under ground in rodent burrows! We can be certain that it is lack of birds, not lack of effort, that is responsible for these low numbers. The square has received over 29 hours of attention in the breeding season, mostly from the indefatigable Joe Barth. The square contains only two complexes of mesquite hummocks and one large paloverde tree. Squaw Peak itself, which might have been a nesting site for a pair of Prairie Falcons or Great Horned Owls if undisturbed, is a center of off-road vehicle activity. The rest of the square is more or less degraded open creosote bush scrub. All other squares have 16 or more possibly breeding species. Not a good recommendation for the coexistence of wildlife and off-road vehicles!
Which volunteer has put the greatest effort into the project? Effort can be measured in several ways, by the hour or by the bird. Aside from our grant-funded field assistants Lori Hargrove, Joe Barth, and Dave Seals, each of which has also contributed many volunteer hours, we must recognize Rich & Susan Breisch as our leaders, with 1386 hours, breeding seasons and winters combined. Jim Wilson and Ed Hall are not far behind with over 1000 hours each. In terms of number of records in our database (each record is a report of one species on one date) Pete Ginsburg is way out ahead with 17,420. Covering all those bird-rich riparian areas in northwestern San Diego County gave him quite a boost. Joe Barth, Ken Weaver, Rich & Susan Breisch, Ed Hall, Kirsten Winter, Pete Famolaro, and Lori Hargrove have all contributed over 9000 records each.
Did you find this game entertaining? Please suggest some other questions and we'll play again in the next Wrenderings!
Sketch from Key to North American Birds, Elliott Coues