Commentary : Bird’s Song Sounds Call for Action

Throughout the river valleys of San Diego County, the cheetle-cheetle-chee , cheetle-cheetle-choo call of the least Bell’s vireo can be heard.

Your reaction may be “so what,” but it is a sound that causes heavy-equipment operators to turn off their engines and elected officials to reach for the aspirin. Dozens of people are listening for this call along our rivers, and hundreds more are highly concerned about what they find.

Little of our regional wildlife has caused as much uproar as has the Bell’s vireo (the “least” differentiates our subspecies from the Eastern races of the same species). Weighing only a few ounces, this small unspectacular songbird has stopped dozens of earthmovers, graders and bulldozers in their tracks.

Such major projects as Pamo Dam and highway bridges on the San Diego, Sweetwater and San Luis Rey rivers have been delayed at least in part as a result of the Bell’s vireo recently being added to the nation’s growing list of endangered species.

The federal Endangered Species Act requires that the breeding habitat of endangered species not be decreased in total extent. Before projects in the nesting areas of the vireo can proceed, other potential nesting areas have to be set aside to make up for the lost habitat. The vireo’s habitat of choice in the county is densely vegetated river valleys, which are also referred to as prime riparian corridors. It prefers streams that have both young willows for nesting and mature canopy trees for feeding.

Local conservationists are united in seeking protection for the county’s greatly depleted numbers of Bell’s vireos. But to fully understand the least Bell’s vireo issue, it must be appreciated that the vireo per se is not the central issue; it is only a symptom of the main issue. It is in a sense the proverbial canary in a coal mine: if the vireo is in trouble, it indicates that there is a larger, more serious problem.

The larger problem, and the real issue, is the accelerating loss of prime riparian habitat. Prime, or mature, riparian habitat is the second-most productive natural zone in San Diego County, the first being coastal wetlands. All seven endangered species of birds in San Diego County are associated with one or both of these two habitat types, which together equal less than 1% of the county’s area.

Unfortunately, the vast majority of the county’s original river stretches containing mature, multistory vegetation have been destroyed. On the lower San Diego River, but only around Padre Dam and parts of Santee, and just east of Interstate 15, can such vegetation be found. Almost none at all is left on the San Dieguito River below Lake Hodges. Other than around California 94, only scattered patches remain on the Sweetwater.

On the San Luis Rey River below Wilderness Gardens County Park, the only remnants exist in the vicinity of the Bonsall bridge and just east of Interstate 5. Somewhat more remains on the Santa Margarita River, but a large part of that will go if the proposed Fallbrook Dam is built.

The important point here is that the decrease in prime riparian habitat is not a problem just for the least Bell’s vireo. Several other declining species also depend on the same habitat, including yellow warbler, willow flycatcher, yellow-breasted chat, downy woodpecker, blue grosbeak, long-eared owl and many others. The yellow-billed cuckoo has been almost extirpated from the streams of the county over the last few decades.

Thus, when conservation groups express concern for the Bell’s vireo, this songbird is also acting as the standard bearer for a large number of other species that similarly depend on mature riparian habitat. It’s a class-action defense, so to speak.

Our real planning challenge in San Diego, then, is to preserve the small remaining portions of our prime riparian corridors. Do this, and we will preserve the least Bell’s vireo. Conversely, fail to do this, and the headlines soon will be filled with the names of a half-dozen other threatened species, all now equally as unknown to the development community as was the Bell’s vireo a few years ago. This is a scenario that no one will profit from and that nobody wants to see happen.

The effort to preserve the nesting areas of the vireo is being coordinated by the San Diego Assn. of Governments, through an interagency Bell’s vireo habitat management task force. Their efforts should be supported by all San Diegans, as it is the only mechanism by which both the vireo can be protected and the stalled construction projects can go forward.

However, this planning effort should be expanded to protect all remaining prime riparian habitat in the county, lest by present inaction we invite more loss of breeding territory, more endangered species, more planning problems and more unnecessary building delays.

The least Bell’s vireo and the various stalled construction projects do not constitute a zero-sum game. There is no reason it can’t be a win-win situation, but only if we do adequate planning now to identity, set aside and perpetuate our remaining prime riparian woodlands. The call of the least Bell’s vireo should become the permanent musical symbol of far-sighted, intelligent resource planning in the San Diego region.

This is what local conservationists really want.