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

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San Diego County Bird Atlas

 

 

CONTACT:
Phil Unitt
Phone: 619.255.0235; Fax: 619.232.0248; Email: birds@sdnhm.org

Bird Atlas,
San Diego Natural History Museum
P.O. Box 121390
San Diego, CA 92112-1390

After the Fires: Bird Recovery in San Diego County

Burning 51.4 square miles on the east slopes of San Diego County's mountains in July and August 2002, the Pines Fire was at that time the second-largest fire in San Diego County history. Though since dwarfed by the fires of 2003, the Pines Fire gave us a head start, so to speak, in assessing the effects of large-scale fires on southern California's biology. Coming so shortly after the completion of field work for the San Diego County Bird Atlas, many bird atlas participants volunteered to help monitor birds' recovery from this fire. With the sponsorship of the Joint Fire Science Program, California State Parks, and the U.S. Forest Service, we established 38 survey routes in and near the burned area, routes corresponding with our bird atlas grid, enabling before-and-after comparisons. We survey each route three times in the winter and four times during the breeding season from 15 April to 15 July. Sponsorship of California State Parks has allowed us to establish five bird-survey routes to assess the effects of the fire in Cuyamaca Rancho State Park, which burned almost completely during the Cedar Fire of October 2003.

Only two species appear to have been wiped out of the area burned in the Pines Fire, the Pygmy Nuthatch and Black-tailed Gnatcatcher. Both of these had occurred only marginally in the area before the fire: the nuthatch lives in pine forest, the gnatcatcher in desert scrub, while the Pines Fire burned mostly chaparral. Some common chaparral birds, however, were dealt a big setback by the fires and are still a long way from recovery. The species most deeply affected appear to be the Bushtit, Wrentit, California Thrasher, and Bewick's Wren. These are all weak-flying nonmigratory birds. Few of them in the path of the fire likely survived, and individuals outside the fire perimeter are slow to disperse into the burned are to recolonize it. In a study of fire ecology on which I worked for the Forest Service in the 1990, we found the Wrentit and Bushtit to be the 2nd and 11th most abundant birds in mature chaparral near Pine Valley. In the Pines Fire area, the Wrentit was 68th in order of abundance in 2003, 49th in 2004. The Bushtit was in 56th place in 2003, 35th in 2004. At the San Diego Audubon Society's Silverwood Wildlife Sanctuary, completely burned in the Cedar Fire, resident manager Phil Lambert had found neither the Wrentit nor the Bushtit recolonizing by November 2004.

Fortunately, the Bushtit and Wrentit are so common in unburned areas that their recovery from even the fires of 2003 seems assured. The California Gnatcatcher, however, undoubtedly suffered a more significant loss: within the United States, 28% of the remaining habitat believed by the U.S. Fish and Wildlife Service to be suitable for this threatened species burned in 2003. By analogy with similar small sedentary birds, few California Gnatcatchers within the burned areas survived.

Long-lasting negative effects are likely also in the Cuyamaca Mountains, almost completely burned in the Cedar Fire. The coniferous forest on the Cuyamacas is rather isolated from similar forests on Volcan Mountain and the Laguna Mountains, and these nearest forests were also partly burned in the Cedar and Pines fires. Therefore forest animals wiped out by the fires, if their ability to disperse is low, may have a hard time recolonizing. Furthermore, the ability of the forest to regenerate itself is an open question: Is our climate now so warm and dry that some of the species of trees making up this forest, already at the margin of their range, will not be able to reestablish themselves?

Comparison with results of the San Diego County Bird Atlas shows three rare species of birds apparently wiped out of the Cuyamaca Mountains by the fire: the Red-breasted Sapsucker, Red-breasted Nuthatch, and Golden-crowned Kinglet. Each of these had a small outlying population in the area, all fairly recent colonizations. In all three cases the population was probably resident and therefore present to be killed when the fire swept through in October. Small isolated populations of five other species survived: the Olive-sided Flycatcher, Dusky Flycatcher, Yellow-rumped Warbler, Green-tailed Towhee, and Fox Sparrow. In each of these cases the population was migratory so was gone when the fire came through. In four runs of five survey routes, we had only a single Brown Creeper and one pair of White-headed Woodpeckers. Therefore it looks like the isolated populations of these two species barely squeaked through-and may not be large enough to be self-sustaining. Continued surveys are needed to reveal whether these (or some other much-reduced species) will make it. A question on which we still have no data is the status of the rare owls, the Spotted and Saw-whet, whether these small populations made it through.

Unburned enclaves played a significant role in birds' survival of and recovery from both the Pines and Cedar fires. On Cuyamaca, the formerly most abundant species, the Mountain Chickadee, is almost absent except in the unburned enclaves. The Pygmy Nuthatch has been wiped out except from these enclaves, but it survives in small numbers in the small enclaves near the top of Cuyamaca Peak, in Paso Picacho Campground, and at Los Caballos near Cuyamaca Lake. This species that forages primarily among the bases of pine needles remains only where there are still green pine needles. Still, it nested successfully in Paso Picacho Campground, at least.

Some birds were affected by the fires surprisingly little. Medium to large birds of the canopy, such as the Acorn Woodpecker and Steller's Jay, appear to have fared much better than small birds of undergrowth. Summer visitors had departed by the time the fires burned in October 2003. When they returned the following March and April, some species reoccupied the same habitat where they had lived before the fire, even forest that had been completely scorched. This led to odd combinations: Violet-green Swallows, Ash-throated Flycatchers, and Western Tanagers being just as common as before the fire, in burned forest almost lacking the typical resident birds.

A surprising variety of birds preferring more open habitats has moved in to exploit the burned area. The Mourning Dove was the most abundant bird in the Pines Fire area in both 2003 and 2004. In the burned forest of the Cuyamaca Mountains the Mourning Dove was the second most abundant species, in habitat where it was uncommon before the fire. The House Finch also became far more common in the Cuyamaca Mountains than previously. Some notable examples from the Pines Fire area include the Northern Mockingbird, Horned Lark, Lark Sparrow, and Western Meadowlark. In spite of being nonmigratory and terrestrial, the Mountain Quail recolonized the Pines Fire zone aggressively. Some of the coveys of Mountain Quail (including large numbers of young) seen there in 2004 were larger than any recorded anywhere in San Diego County over the 5 years of the bird atlas study, 1997-2002. Lawrence's Goldfinches proliferated, feeding heavily on the seeds of fire-following wildflowers, especially those of the family Boraginaceae. The most conspicuous fire-following bird is the Lazuli Bunting, the 4th most abundant species in the Pines Fire area in 2003. In the Cedar Fire area, along Highway 79 through Cuyamaca Rancho State Park, the song of the Lazuli Bunting became the primary bird sound in 2004.

In the Pines Fire area, postfire succession is underway, with some shrubs already at two-thirds their mature height by summer 2004. At least 25 species of birds increased in number from 2003 to 2004. In some species, the increase from 2003 to 2004 was so sharp as to suggest the vegetation had recovered to a point beyond some threshold requirement, allowing large numbers to move in. This was especially clear for the Black-chinned Sparrow, a migratory bird whose numbers from year 1 after the fire to year 2 increased by a factor of 20. Over the same period, on the other hand, numbers of the Lazuli Bunting in the Pines Fire area decreased.

Birds' response to wildfire has been studied so little that I have little basis on which to make any predictions. I found that Costa's Hummingbirds proliferated along with the plants on which they feed in small burned areas near Pine Valley in 1993. Yet the hummingbird failed to repeat this performance following the Pines Fire-possibly because of the drought continuing after the fire. Though fire has long been basic to the ecology chaparral, fires the size of those in 2003 are unprecedented in historic times. Furthermore, they burned in an environment far more checkered with human settlements and exotic weeds than previously. The fires have reminded us that environmental change is constant, and sometimes far more rapid than we had been raised to expect. Do these fires mark a turning point in evolution, after which we will see a community of plants and animals much different than in the past?

Contact: Phil Unitt
Phone: 619.255.0235; Fax: 619.232.0248; Email: birdatlas@sdnhm.org
Bird Atlas, San Diego Natural History Museum, P.O. Box 121390
San Diego, CA 92112-1390