Bell’s Vireo May Be Protecting Quality of Life

It’s hard to imagine a 5-inch-tall songbird being the subject of rampant controversy and vilification, but since the least Bell’s vireo was recently added to the federal government’s Endangered Species List, that’s exactly what has happened.

The bird is being blamed for “halting” numerous highway projects, flood-control projects and dam proposals in San Diego County. It has been called “dull,” “ordinary,” “drab,” “stupid” and “inflexible” by reporters and editors. The U.S. Fish & Wildlife Service, which designated the bird as endangered, is labeled a “bureaucracy letting policies override good common sense” and accused of “placing more value on bird than human life.” Thus has a deluge of misinformation been presented to a public that for the most part has never seen or heard a least Bell’s vireo.

But why all the anger and misleading press? Here are some facts about vireos and their impact in greater San Diego County.

The “dull” and “drab” adjectives applied to the vireo refer to the color of its back, which is a soft gray. A faint yellowish tinge may be discerned along the bird’s side. The underparts are white. Two white wing bars and a faint eye-ring further help identify the vireo. To the novice bird watcher, this description may not be of much use. Locating a least Bell’s vireo in the field, however, is made simple by its loud, cheery song--Cheedle cheedle chee? Cheedle cheedle chew!

The male vireos arrive in Southern California in March and April and set up territories in the riparian woodlands that line the rivers here. The vireos mate, nest and raise their young in these same territories, obtaining food, shelter and nesting materials from the native vegetation such as oak, cottonwood and sycamore trees, several types of willows and the plants associated with them. By mid-August, the vireos have flown south to their wintering grounds on the tip of Baja California or mainland Mexico.

These small songbirds are amazingly resilient and defend themselves and their territories quite aggressively. Nesting pairs attack scrub jays, snakes, people and other intruders that threaten their eggs or young. Vireo pairs have been known to build as many as five nests in one season, and vireo females may lay 12 eggs or more in an effort to raise young to adulthood. Least Bell’s vireos are not defenseless, shy, retiring, or poor reproducers. So why are they endangered?

One of the most serious misconceptions brought forth by the press and others is that the least Bell’s vireo has become endangered solely due to its interaction with another bird species, the brown-headed cowbird. This is simply not true.

The brown-headed cowbird, a brood parasite that lays its eggs in other birds’ nests, is contributing to the decline in vireo numbers by decreasing the success rate of vireo nests. However, despite some newspaper accounts to the contrary (“vireo doesn’t have an eye for survival, never seems to notice the other bird’s egg”), cowbird parasitism is not the primary reason for the vireo’s decline.

The least Bell’s vireo is an endangered species because of the loss of habitat due to destruction by man of riparian woodlands. More than 95% of the vireo’s historic breeding area has been destroyed. Most of the remaining breeding localities are in San Diego County.

Why? Mostly because San Diego County does not have as many concrete flood-control channels as does, for instance, Los Angeles.

Ever seen the Los Angeles River? It is hard to believe that once live oak, sycamore, willow, cottonwood and a host of other tree and plant species lined the banks of what is now concrete, gravel and polluted water. Least Bell’s vireos once bred among the lush greenery of the Los Angeles River, just as they do now along many of our county’s scenic river valleys.

We in San Diego should be thanking the least Bell’s vireo for bringing to our attention the destruction of one of our most precious natural resources--the oak-riparian woodland. Protection of the vireo’s habitat will ensure that Southern California’s only lowland native woodland is preserved. Additionally, riparian habitat protection will preclude the necessity of the federal Fish & Wildlife Service declaring endangered several other species that are equally threatened because of loss of habitat.

Another fallacy regarding the vireo is that their mere presence will “halt” many projects. Protecting the oak-riparian habitat will not endanger human lives by halting desperately needed highway projects. Not one project will be canceled because of the presence of vireos.

Some delays are being encountered while acceptable mitigation plans for the various projects are being developed. But the purpose of the proposed mitigations is not to stop essential projects, but to insure that the potential impacts of these projects are mitigated to a level of insignificance, mainly through preservation or replacement of riparian areas.

For example, a current Caltrans project involving the replacement of the California 94 bridge over the Sweetwater River was mitigated by enhancing bordering habitat and funding a two-year cowbird trapping and vireo study project. Construction began in March, despite newspaper accounts that the bridge project “has been blocked by the vireo.” Efforts such as these by Caltrans and other agencies will ensure that essential projects will be completed with as little disturbance to our latest federally endangered bird and its habitat as possible.

The least Bell’s vireo may even save taxpayers money by causing planners to study alternatives to non-essential, costly projects proposed along our waterways. Building in river channels can cost government billions of dollars, not only in initial channelization costs but in subsequent disaster relief aid made necessary when the river inevitably abandons its artificial restraints and floods out those who built in the lowlands.

There are many biological, agricultural, economic and aesthetic benefits to not developing flood plains. After all, we like San Diego County for some of the same reasons that least Bell’s vireos do. More freeways, more blacktop and more flood-control channels where riparian woodland once flourished will not make the San Diego area a better place to live, whether you are a Homo sapiens or a Vireo belli pusillus .