White-Tailed Kite, Specter of the California Skies by Cheryl L

SPRING 2014 Volume 37, Number 1 White-Tailed Kite, Specter of the California Skies by Cheryl L. Davis areas – areas that can support great abun- note that the California vole (Microtus cali- You have likely seen these graceful, dances of rodents. fornicus) is the main food source for white- white raptors hovering above Bay Area Their ability to adapt to disturbed tailed kites. Though there are researchers grassland and marshes, their beating wings habitats have expanded their range from the who claim the evidence for this statement suspending them in air like a ghostly appari- southern United States, along the coast of is based only on circumstantial evidence; tion or angel. With their head bent towards Oregon, Washington and California, and such as observing changes in white-tailed the ground, they quietly hover, scanning the ground for unsuspecting prey. The white-tailed kite (Elanus leucurus), formerly called the American black-shouldered kite, has white underparts, a long, mostly white tail, and pointed wings. While juvenile underparts and head are lightly streaked with reddish/reddish orange color, both adults and juveniles, when viewed from above, show black shoulders in flight as the black leading edge of the inner wings, hence the earlier accepted common name of the black-shouldered kite. When viewed in flight from below, this edge appears as small black patches. One of the smaller raptors, it has a body length of 16 inches and wing span of 42 inches. The white-tailed kite is a species well suited to thrive in many habitats available in California. Their distinctive hunting technique coupled with their unique coloring distinguishes them readily from Aric Crabb/Bay Area News Group other raptors in the field. White-tailed kites hover about 100 feet in the air and drop to south through Middle America and parts kite numbers in response to changes in the ground rather than using “stooping,” of South America. They forage and nest in the abundance of this vole. Additionally, a foraging method of hawks and eagles low elevations, avoiding areas which have since the vole is not a desert species, kites which employs a steep dive to surprise extensive winter freezing patterns. in southeastern California are not likely to prey. Even among other North American Though vegetation structure and prey depend on this animal as a primary food kites, they are the only kite to employ this abundance have been noted to be the most source. Also consumed are other rodents hunting technique. This allows them to important parameters influencing habitat (house mouse and western harvest mice), forage in areas with denser vegetation, when choice, most researchers agree that prey lizards, and insects, but rarely birds. necessary, such as chaparral. Other types of abundance is the most important popula- The core of the white-tailed kite breed- habitats used by the kite include grassland, tion regulator. Small mammals make up oak woodland, wetlands, and savannah-type about 98% of their prey and many studies continued next page from page 1 ing range in the United States is California. They are common in the Central Valley and along the coast of California. When nesting, white-tailed kites can generally be found in riparian areas adjacent to open areas and dense, broad-leafed deciduous trees are preferred for nesting and roosting at night. Historical accounts from the late 19th century have also documented them nesting in large stands of oaks in oak woodland habitat. Nests made of sticks are usually found in single isolated trees in large stands and they also use larger shrubs generally less than 10 feet tall. Nest building occurs from January through August and egg-laying begins in February, with peaks of egg-laying occurring in March and April. The building of nests is truly a partnership between the two sexes. The male collects the nesting material where Suitable habitat for white-tailed kites. Photo: Ambarish Goswami he would then hand them off to the female kites having three clutches with new nests to 1991. This species is a fully protected to create the perfect bowl-shaped home. The being built for each clutch. Incubation takes species by the State of California under the well-made nest would sit in the fork or top approximately 30 days. It has been docu- Department of Fish and Wildlife. of a tree or tall bush, usually lining the nest mented that abundant food or a clutch of In the 1960s, the State of California with dry grass or straw from nearby agri- eggs being destroyed or stolen can prompt made an initial effort to provide extra cultural fields. Due to the kite’s preference white-tailed kites to lay a second clutch. A protection to animals that were rare and for building the nest in dense vegetation, late 19th century article by one of the found- faced possible extinction. Lists were created the nests are quite difficult to spot from the ers of the journal Condor, describes the providing this additional protection for ground. During the incubation period, the author climbing to several white-tailed kite fish, mammals, amphibians and reptiles, male spends his days hunting for food for nests that were over 20 feet off the ground and birds. Fully protected species may himself, his mate, and for the newly hatched and stealing the clutch for collectors and not be killed or possessed at any time and young. This behavior would continue until museum specimens. Often the same nest no licenses or permits can be issued for the young has fledged. was robbed twice in one season! their destruction or possession expect for Most chicks fledge in May and June This species has had a difficult history necessary scientific research. Relocation of and the fledglings continue to depend on in California. While historically common some bird species is allowed for protection parent raptors for about one to two months. in the lowlands and marshes of California, of livestock. It has been suggested that white-tailed kites white-tailed kites were pushed to the edge Some fully protected species have also of extinction around the arrival of the 1930s been listed as threatened or endangered by habitat loss, shooting, and egg-collecting. species under the more recent endangered Fortunately, their numbers and distribution species laws and regulations. Though the increased between the 1940s and the 1970s, white-tailed kite is not listed as threatened and into the early 1980s. This increase or endangered under the federal Endangered has been speculated to be caused by some Species Act, administered by the United protection for the species itself and an States Fish and Wildlife Service (USFWS), increase in agricultural development with this species also receives protection under a corresponding increase in rodent habitat. the Federal Migratory Bird Treaty Act, California vole. Photo: USFWS Ungrazed or lightly grazed fields provide the also administered by the USFWS. This largest prey populations as opposed to row law, originally issued in 1918, but updated seldom forage more than a ½ mile radius crops, vineyards, and orchards. subsequently as needed: “makes it illegal from their nest sites and nest sites have been But even with this good news, a bird for anyone to take, possess, import, export, closely associated with habitat that supports breeding survey in California conducted transport, sell, purchase, barter, or offer for dense rodent populations. between 1980 and 2006 noted popula- sale, purchase, or barter, any migratory bird, White-tailed kites are known to have tions of white-tailed kites in southwestern or the parts, nests, or eggs of such a bird two or even three clutches of eggs in a single California may be declining due to urban except under the terms of a valid permit season, with clutches containing between and commercial development, with the issued pursuant to Federal regulations.” three and six eggs. Accounts from the late most significant decline occurring in However, even with such protections in 19th century described a pair of white-tail Southern California grasslands from 1982 place for individual birds, nests, and eggs, Page 2 protection from loss of foraging, breeding, The elimination of hedge rows, edge mitigation properties in Contra Costa, and roosting habitat due to urbanization can vegetation, or riparian vegetation near or Alameda, and San Joaquin Counties. Her be more difficult to ensure. That this species surrounding agricultural fields could impact work includes protecting and enhancing usually exists within a hunting guild, a col- some of the foraging habitat that has helped populations of many special status animal lection of raptors and birds using the same the white-tailed kite recover its numbers. and plant species, such as California tiger foraging area and resources, makes habitat The California vole needs habitat with salamander, California red-legged frog, loss significant for the white-tailed kite as adequate ground cover and does not inhabit golden eagle, and burrowing owl. She well as multiple other winged species. bare, mowed, or heavily grazed habitats. received her M.S. in Biological Sciences Construction projects, whether public Government protections will continue from California State University, East infrastructure, urban growth, or suburban for this species as will California’s efforts to Bay, where she remains an Associate sprawl may mitigate for their impacts to preserve and restore wetlands and marshes, Researcher in Dr. Christopher Kitting’s habitat by purchasing/protecting similar along with private efforts to preserve Hayward Shore Laboratory. habitat. But locating available similar agricultural land from development. With habitat adjacent to, or within an established these measures and the continued resilience habitat range or breeding area of the and adaptability of white-tailed kites, this white-tailed kite or other raptor and bird specter of California skies can hopefully species can be difficult, if not impossible.

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