spatial profile
The Least Bell’s Vireo is one of four recognized subspecies of Bell’s Vireo. Breeding entirely in California and northern Baja California, the Least Bell’s Vireo is the westernmost of the subspecies. The average territory size of the Least Bell’s Vireo is .5 to 7.5 acres.
Habitat requirements
The Least Bell’s Vireo need specific habitat requirements in order to survive. They require low-growing and dense thickets of mugwort, mulefat, and California wild rose. They live in areas that contain tall willows, cottonwoods, and sycamore trees. During winter months, the Least Bell’s Vireos live in mesquite scrub vegetation. They also are known to forage in nearby chaparral and coastal sage scrub, but do not live in these areas.
History
The Least Bell's Vireo was once considered one of the most prominent birds in all of California. This changed between the years of 1930 and 1985 when the population decreased largely. In the year 1986, it was estimated that only 300 pairs remained. At that point the species was labeled as endangered and the population increased to 1,300 pairs by the year 1996 and 2,500 in the year 2004. The bird remains on the Endangered Species List to this day.
Changes in distribution
It has been observed that throughout history the Least Bell’s Vireo could be found in a lowland riparian habitat ranging from the coast of southern California through to Sacramento as well as the San Joaquin Valley and even as far north as Red Bluff/the Tehama county. The species was also found in the foothill streams within the Sierra Nevadas and Coast Ranges as well as in Owens Valley and Death Valley and occasionally in the Mojave Desert.
In the year 1986, the Least Bell’s Vireo was entered into the United States Fish and Wildlife Service. At this point only 300 pairs of the species remained throughout the state of California. They were no longer confined to the areas they previously had lived. Now, they were confined to only eight different counties. Each of these counties were south of Santa Barbara and a majority of the remaining population resided in the San Diego County. The population later expanded back to some of the previous locations it was originally found. In the year 1998, 67 pairs nested near the Santa Clara River in Ventura County. Some of the population was also found in the Mojave Desert in the same year. In the year 1997 there was a sighting near Gilroy in the Santa Clara County which was the northernmost sighting to be recorded. In 1998, nearly half of the population resided in San Diego on drainages in Marine Corps Base Camp Pendleton.
Distribution for the Least Bell’s Vireo varies slightly from what is explained above. The population mainly resides in southern Baja California, Mexico.
In the year 1986, the Least Bell’s Vireo was entered into the United States Fish and Wildlife Service. At this point only 300 pairs of the species remained throughout the state of California. They were no longer confined to the areas they previously had lived. Now, they were confined to only eight different counties. Each of these counties were south of Santa Barbara and a majority of the remaining population resided in the San Diego County. The population later expanded back to some of the previous locations it was originally found. In the year 1998, 67 pairs nested near the Santa Clara River in Ventura County. Some of the population was also found in the Mojave Desert in the same year. In the year 1997 there was a sighting near Gilroy in the Santa Clara County which was the northernmost sighting to be recorded. In 1998, nearly half of the population resided in San Diego on drainages in Marine Corps Base Camp Pendleton.
Distribution for the Least Bell’s Vireo varies slightly from what is explained above. The population mainly resides in southern Baja California, Mexico.