Mapping and Modeling
With the fall's being our "down" season for atlas field work, do you think that Ann Klovstad and I are taking a break from the project? Think again! This year, the fall has provided us with an opportunity to move forward on aspects of the atlas critical to maximizing the usefulness of our data and presenting them in the final products. As we mentioned in the last Wrenderings, we are now able to take advantage of both improved hardware and improved software--the latter in the form of the latest version of the computer-mapping program ArcView, made possible by a generous gift from Mike Mathos. We have also upgraded another key component of software--our brains. Richard Wright of San Diego State University's geography department kindly arranged for Ann and me to take the training course in ArcView taught by John Kaiser. In 12 one-hour sessions at breakneck speed we learned this program's astonishingly diverse capabilities. Each class revealed some new feature applicable to the atlas. Barbara Bell, atlas participant and computer mapping expert for Camp Pendleton, kindly lent us her Veterans' Day holiday to work with us hands-on and answer specific questions. We are now able not only to display individual species' distributions flexibly, we can move on to the next step of analysis and interpretation.
Being able to discern and describe patterns in nature is in itself immensely gratifying. But the human mind always asks the next question: why? What factors explain the distributions we observe? How are birds constrained by--or taking advantage of--vegetation, temperature, rainfall, land use, and size of patches of their habitat? Computerized maps of many of these variables are now available. Corey Ferguson, computer mapping expert with the U.S. Forest Service, has assembled these for us and rendered them compatible with our bird atlas grid system.
Answering questions like these entails the process of modeling. Modeling means finding the combination of factors that, when plotted on a map, matches the observed distribution most closely. Finding this combination, though, takes some imagination and creativity, since we're not yet able to automate the process entirely. Models can be simple or dizzyingly complex. For an example of a simple model, let's take the House Sparrow. In San Diego County, House Sparrows live around buildings and don't live in any natural habitat. Therefore, we can propose a model that consists of just one factor, the areas designated "urban/developed" in the vegetation map, and compare it to the House Sparrow's observed distribution. As you can see, the correspondence is good but not exact. In some remote areas scattered rural residences lack House Sparrows, and some squares in the Anza-Borrego Desert with campgrounds, not mapped as developed, have them. In the city, we also see a few squares, still short of their thresholds, where House Sparrows should be expected but have not yet been recorded.
Let's move on to a more complex and more interesting example, the Mountain Quail. Corey is working with us on developing the models, and we selected the Mountain Quail for our trial run. This species occurs in both coniferous woodland and chaparral. So to start the model we selected all types of coniferous woodland on the Forest Service's vegetation map plus six types of chaparral. Over most of San Diego County the Mountain Quail is confined to the higher foothills and mountains, so we added an elevation requirement--2000 feet minimum elevation appeared to work best. In far northwestern San Diego County, though, the Mountain Quail extends to lower elevations. By eliminating the 2000-foot requirement in the Santa Ana Mountains ecoregion, then, we got the result portrayed here, our closest approximation to what we've actually observed. (The various ecoregions the Forest Service has defined in California, on the basis of broad physiographic criteria, can be seen on its website, www.r5.fs.fed.us/ecoregions/ca_sections.htm.) Further fiddling trying to incorporate criteria based on rainfall or temperature didn't improve the model perceptibly.
The model looks pretty good, picking up isolated sites for the Mountain Quail like the Santa Rosa Mountains, Vallecito Mountains, Otay Mountain, and even McGinty Mountain in square R16. But it isn't perfect, prompting more questions. In some cases, the discrepancies reflect the few squares where our coverage is still poor or lacking. In some, they reflect deficiencies of the vegetation mapping--the Forest Service's vegetation map for the Anza-Borrego Desert is very coarse. But in others they reflect more interesting questions. The model predicts the Mountain Quail on Iron Mountain (M13) but we haven't observed it there--since we initiated the atlas. Previously, though, Margaret McIntosh noted it there and suggests it was eliminated by fire. A site isolated by several miles from the next nearest suitable habitat may be difficult for a bird as sedentary as the Mountain Quail to recolonize. The model predicts the Mountain Quail in several squares along the Mexican border where we have no records. Is there some additional limitation on the Mountain Quail we haven't yet recognized?
Another important task we embarked on this fall is getting the locations for scarce and sensitive species plotted on the daily field maps into computer memory. Thanks to an agreement with Tom Oberbauer and Bob Asher of the county department of planning and land use, Melanie Casey and Dan Henderson, computer-mapping experts with the county, are providing this service, in exchange for our providing the atlas database to the county. Readying our diverse field maps for Melanie and Dan, though, is a monumental task in itself. Thanks to Ann Klovstad for taking charge of this complex problem and for thinking up its most efficient solution--assigning an identifying number linking the plotted points to the corresponding record in our database. Thanks to Joan Dudley, Margaret McIntosh, and Lori Hargrove for their helping with this task. Don't be surprised if you get a phone call or e-mail message from one of them asking for a clarification. And thanks to everyone who took the time to plot these locations. More precise locations, linking our observations to patches of known vegetation type and known size, will make the models for these species more precise and more useful in conservation. Again, we urge everyone to plot all species tagged on the atlas forms with an asterisk; we are glad to send you maps of any area for this. The more precise and thorough our data, the more useful are our results.
-- Philip Unitt
San Diego Bird Atlas Attack Force
With the five years of field work for the San Diego bird atlas nearing its conclusion, we see many squares that need a relatively modest effort to be put over their threshold. Many of our participants have already reached their thresholds in their adopted squares and are looking for means to contribute further. Therefore, at the suggestion of the project's advisory group and some of our key participants, we're initiating a new mode of covering the county to supplement those we have already: an attack force. To those who join our attack force, we will distribute a list of squares needing that extra push. When you want to make a field trip, select one of these of interest to you, then call Ann or me and we will send you maps and target list. Send in your results immediately, and we will update the attack force's list. We will also organize one-day field trips, mini-blockbusters if you will, to cover targeted squares, sometimes on week days. Adoptions of squares and blockbuster weekends as we have organized them in the past remain as critical as ever to our success--we hope that this new method will only add more flexibility and speed us ever more quickly toward our goal. So if you can help in this way, please join the attack force now!
Please consider joining us for one or more of these overnight field trips that have proven so valuable in covering the county. You're welcome for one or both days.
For the past three years, we have gathered our flock at various locations throughout the county for our infamous WingDings. Each of these events has had its own unique flavor, and the flavor of the Fall WingDing was most definitely Bar-B-Que!
About 120 bird atlas participants escaped the heat on September 16th and enjoyed the cool shade of Jeffrey Pines in the Laguna Mountains. Many hiked the short trail to Laguna Meadow for a bit of birding but most just welcomed the opportunity to socialize and eat! After lunch, Phil gave a brief update on our progress, and once again we were delighted to recognize breeding-season threshold-clearers. Those who cleared the threshold in at least one square received "A Birder's Year" engagement calendar featuring stunning bird photography, those who cleared it in two squares also received a binocular strap from La Mesa Camera, and those who cleared it in three or more squares also received a gift certificate to the museum store.
But no one went away empty-handed from this WingDing, thanks to Frank and Betty Scheible, Ann Klovstad's parents. They had asked Nicole Perretta to design a button for the bird atlas project, to be given to all of the project's dedicated volunteers. These great buttons are for everyone who attends a WingDing, so if you want to add to your growing collection of bird atlas attire, attend a WingDing! Thank you, Frank and Betty and Nicole!
And thanks once again to the Road Crew (Kathy Estey, Cheryl Mann and Joan Roberts) for assisting with check-in, to Philemon and Angie Parker of Phat's Bar-B-Que for keeping our plates full, to Janet Chenier of the museum store for providing the gift certificates, and to Ronnie Schneider, Director of Special Events at the Natural History Museum, for her invaluable assistance. A special thanks to Kirstin Winter of the U.S. Forest Service for hosting this event in the beautiful Laguna Mountains and to the National Fish and Wildlife Foundation for the recognition gifts.
We're already working on arrangements for the Spring 2001 WingDing. Mark your calendars for the morning of Sunday, 25 March 2001. We'll meet in Mission Bay for a morning of birding along the San Diego Flood Control Channel, then move to the Marina Village complex in Quivira Basin for a post-birding breakfast and program. Once again, we'll award those cool bird atlas hats to participants who have cleared the winter threshold in one or more of their assigned squares.
There are only a few WingDings left on the calendar (Spring and Fall 2001 and the grand finale in spring 2002), so make every effort to attend. We hope you can join us!
New Field Guide
The new field guide to North American birds by David Sibley, basis of much buzz among birders, is now available. Check it out! It features paintings of many juvenile plumages not previously illustrated in field guides. The museum's store, along with the rest of the museum, is closed for construction from 3 January to 6 April 2001, but this book is available through our online bookstore's association with Amazon.com.
See The Sibley Guide to Birds at Amazon.com.
Cactus Wren button, sketch by Nicole Perretta