Focus On...the American, Lawrence's, and Lesser Goldfinches
The Lesser Goldfinch is one of the most widespread and familiar birds of San Diego County. Our other two goldfinches, though, have interesting twists to their biology and are well worth getting to know better. Especially in winter, when the American changes into a nonbreeding plumage, the less common species can be overlooked, so this is a good season to address this trio.
The goldfinches are members of the family Fringillidae, a group with several interesting distinctions. Among these are a tendency to engage in irregular dispersal rather than regular migration, an entirely vegetarian diet, and failure to remove chicks' feces from the nest--used finch nests are easily identified by their dropping-encrusted rims. Males do not defend a territory for foraging, only the female and a small area around the nest, allowing the birds to nest semicolonially.
Because the Lesser is by far the most numerous of the goldfinches in San Diego County, it is a good starting point. Adult males and females, of course, differ conspicuously by the males' black cap. The males' green above and yellow below are also brighter than the females'. Juveniles are duller still, but in all plumages the Lesser Goldfinch has the underparts uniformly yellow, whatever the shade of that yellow may be. The wingbars of a Lesser Goldfinch, greenish to whitish, are narrow and not very conspicuous--less conspicuous than the white patch in the primaries. Consider the bill of a Lesser Goldfinch: small and conical, though sharply pointed, and dark gray. Lesser Goldfinches make several calls, but they seldom go long without broadcasting their sad, descending whistle, a call unique to the Lesser. In their song, males incorporate mimicry of other birds. Listen carefully to a singing Lesser Goldfinch, and you can often pick up the calls of birds like the American Kestrel, Rock Wren, and Western Wood-Pewee.
The American Goldfinch differs from the Lesser in its seasonal plumage change. In summer the yellow-and-black male is obvious, but in fall and winter the yellow is replaced by brownish and gray. At this season the wing pattern is the most prominent feature on the bird: broad wingbars, white in adults, buff in immatures, that contrast boldly with the blackish wings. The flight feathers have crisp edges but no white patch. The winter males may have some blotchy yellowish on the underparts but the undertail coverts of an American are always white, those of Lesser always some shade of yellow. The wingbars of a winter American Goldfinch are always much broader than on a Lesser, and the American has no green on the upperparts. In spring American Goldfinches replace their body feathers but not their wing feathers so that by summer their wingbars are worn down and may be no wider than the Lesser's. The bill of the American is larger than the Lesser's and pale at all seasons, dull yellowish in winter, almost orange in the summer male. Despite its scientific name tristis, the American never gives a sad whistle like the Lesser; its twittering calls are practically the same as those of the Pine Siskin. The warbled song of the American is complex and not stereotyped; it somewhat resembles a Lazuli Bunting's song and is not known to include mimicry.
If seen well, Lawrence's Goldfinch seldom presents an identification problem. Usually the birds are in flocks including some striking black-faced males. If females are seen alone, their broad yellow wingbars, pale pinkish bill (stubbier than the other species'), and uniformly pale gray head and underparts, relieved only by a variable yellow patch on the breast, give them away. The juvenile Lawrence's is unique among the goldfinches in having the underparts streaked--though the streaks are soft and inconspicuous. The call of Lawrence's is also unique, a high-pitched bell-like tinkling tinkoo, often given in flight. Learn this, and you will gain a whole new perspective on Lawrence's Goldfinch, and amaze your friends as you identify the birds as they fly overhead, so high they look like specks. The call is so high-pitched, however, it falls out of the range of some people's hearing. The song of Lawrence's Goldfinch relies even more heavily on mimicry than the Lesser's--it may consist of nothing but mimicry strung together with tinkoo notes. Next time you find a Lawrence's Goldfinch singing, entertain yourself by seeing how many mimicked species you can identify. Calls of different species follow each other in such quick succession that your brain will struggle to process information so quickly!
Even though the three species all eat small seeds, they diverge greatly in many aspects of their biology. The Lesser Goldfinch is an adaptable generalist, inhabiting a wide range of habitats, be they native or artificial. Lesser Goldfinches feed eagerly on the seeds of exotic weeds like the sow thistle (Sonchus oleraceus) that proliferate in disturbed soil. They nest as readily in planted eucalyptus trees as in native oaks and sycamores. Our atlas results reveal them distributed almost uniformly over the coastal slope. Only in the Anza-Borrego Desert is their distribution patchy, limited mainly to oases, but occasionally they nest even in washes remote from water, as in Palo Verde Canyon (E28) and Split Mountain (L29).
The American is the most widespread of the three goldfinches in North America but the most restricted in San Diego County. Indeed, we are virtually at the southern tip of its range. It can be seen in Parque Morelos in Tijuana, but otherwise no current sites for it are known in Baja California. As implied by the scientific name of the California subspecies, salicamans, and by the former common name of Willow Goldfinch, the American is basically a riparian species in our region. This habitat preference for streamside woodland, though, is expressed in a way somewhat different from that of other riparian species like the Downy Woodpecker, Bell's Vireo, or Yellow Warbler. The birds' distribution is rather patchy: they are common in some areas with extensive riparian woodland like the Santa Margarita and Tijuana rivers but scarce or absent in smaller patches that still support many other riparian birds. Especially during the nonbreeding season, though, they readily depart riparian woodland to forage wherever they can find concentrations of food. This may take them to residential areas planted with nonnative trees like Liquidambar, whose seeds they extract from their woody fruits, or riparian scrub, where they descend in flocks on sunflowers and the great marsh evening primrose (Oenothera elata). In the foothills and mountains they occur at only scattered locations, possibly irregularly. On the desert slope, they occur in summer only in San Felipe Valley, elsewhere only as a rare vagrant in winter.
Like the Tricolored Blackbird, Lawrence's Goldfinch is one of California's unique natural wonders. It has only a narrow breeding range but is notoriously nomadic. Like the Tricolored Blackbird and Costa's Hummingbird, it is adapted to exploit food sources that are abundant but ephemeral. In the summer, this source is seeds of wildflowers of the family Boraginaceae, that is, the native fiddlenecks and popcornflowers of the genera Amsinckia, Cryptantha, and Plagiobothrys. Above all, Lawrence's Goldfinches seek the striking orange-yellow fiddleneck Amsinckia intermedia, which grows in scattered meadows, often in disturbed soil. In winter, they shift to gleaning seeds from the dried flowers of chamise, the dominant shrub in San Diego County's chaparral. Nevertheless, in most winters most Lawrence's Goldfinches vacate the county. In contrast to the American Goldfinch, Lawrence's is concentrated in the mountains and inland valleys and seldom occurs within 10 miles of the coast. Occasional small flocks do reach and even nest near the coast, though, as Sue Smith observed in pine trees in her apartment complex near the intersection of Del Mar Heights Road and Interstate 5 (N7). Another interesting aspect of Lawrence's Goldfinch's irregularity is its positive response to El Niņo: our desert records are almost all from the spring of 1998, following a wet winter that stimulated desert wildflowers famously. With its vegetarian diet, Lawrence's, like the other goldfinches, must drink regularly, making long flights to water sources scattered through its arid habitat.
Philip Unitt and Nicole Perretta