California Gnatcatcher: Hero of the Coastal Sage Scrub Habitat

Heading down the trail from the San Elijo Lagoon parking lot, he played a wheezy, kitten-mewing type of call on his phone.  “That’s what we’re listening for.”  This good friend and avid birder from Colorado was on a mission—to find a California Gnatcatcher.  Searing that call into our brains, we followed our ears to find a pair of these special birds.

At a mere 4½ inches long, the California Gnatcatcher is a slender, gray bird with a white eye ring and a long, black tail narrowly edged with white.  During the breeding season, the male sports a distinctive black cap.  Females look gray overall, with brownish overtones.  The birds frequently hang out in pairs and tend to be quite vocal.  Their mewing calls often provide the easiest way to narrow down the search area—as they did for us.

Commonly found throughout sagescrub habitats in most of southern and central Baja California, this songbird reaches the northern edge of its range along the coast from San Diego to Ventura counties.  In 2001, estimates placed the populationof these birds in Southern California at fewer than 5,000 breeding pairs; a 2010 study found only 1,324 pairs on 110,000 acre of coastal sage scrub on public lands in San Diego and Orange counties.  But the explosive urbanization, subsequent suburban sprawl, and agriculture conversion within the last 50 years have reduced the species’ coastal sage scrub habitat in California to roughly 10% of its historical range, leading in 1993 to Federal protection of this northernmost subspecies as Threatened under the federal Endangered Species Act (ESA).

California Gnatcatchers prefer food items that aren’t hard to catch, focusing primarily on small, slow (sessile) insects, such as leafhoppers, spiders, or beetles,rather than on more active small insects.  Birds may hover to pluck an orb-weaving spider from her web or to harvest scale insects from the pads of prickly pear.  They often will whack larger prey items against a branch before swallowing them whole.

Mid-March to early July is the main breeding season for California Gnatcatchers in San Diego County.  The female lays a clutch of three or four eggs, which both parents incubate for about 14 days. Youngsters fledge after just 13 days, but parents care for the new generation between three and five weeks after the kids leave the nest.

Gnatcatcher families face many challenges.  Cowbirds frequently parasitize their nests, laying one egg that hatches earlier, producing a larger nestling that grows faster, than the host species; the hulking, aggressive cowbird nestling then outcompetes its smaller foster siblings for food.  As with most other open-cup nesters, California Gnatcatchers are also extremely vulnerable to nest predation by ants, snakes, birds, rodents, and medium-sized mammals, to name just a few. But the species can often offset high rates of nest predation by rapid and persistent renesting attempts throughout itslong breeding season. As many as 10 nesting attempts may occur in a single year, producing up to three successful broods.

The California Gnatcatcher’s scientific name,Polioptila californica, derives from Greek. Polioptila (“gray feather”) comes from polios (“gray”) and ptlion (“down feather”), referring to the bird’s overall color.  Its species name reiterates the species’ natural range in Baja and southern coastal California, as does the first part of its common name.  (To be precise, the SoCal subspecies is P. californica californica.) (from the Department of Redundancy Department)  “Gnatcatcher” refers to a habit of catching tiny insects in the air, although this behavior better characterizes its cousin, the Blue-gray Gnatcatcher.

One ESA-listed species can protect other imperiled species—e.g., coastal whiptail lizard, coastal horned lizard, coastal cactus wren—that depend on this shrinking, specialized sage scrub habitat.  Indeed, for a quarter-century, this small gray songbird has made the difference between land development and conservation on some of the priciest, most coveted coastal lands in California.The gnatcatcher’s listing as a Threatened species in effect moved hundreds of thousands of acres of land in Southern California off the table for development—much to the disgruntlement of property developers. As a lucky bonus, San Diego County’s three major military installations—Camp Pendleton, Fallbrook Naval Weapons Station, the Marine Corps Air Station Miramar—also support important California Gnatcatcher populations.  Thanks to the Sikes Act of 1997, the military is mandated to manage this habitat for these threatened birds. Another check on the plus side, studies suggest that California Gnatcatchers tolerate nearby construction and high noise levels. In fact, nearly 20% of the locations recorded for this gnatcatcher in San Diego County occurred within 500 feet of major roads.  Moreover, although California Gnatcatchers can be eliminated by complete destruction of their habitat, they do not appear especially sensitive to moderate fragmentation of that habitat at a larger scale.

Hated by land developers as their worst enemy, extolled by conservationists for its ability to stop a bulldozer in its tracks, the diminutive California Gnatcatcher carries the burden for fellow sage-scrub-obligate species—a lot of pressure for such a tiny bird.  Yet at least for now, this sprite continues to stand strong to protect one of the planet’s most endangered habitats, along with its web of flora and fauna, from further human encroachment.  Its kitten-like calls ring as powerful as any lion’s roar.