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White-Tailed Kite (Elanus leucurus)
White-Tailed Kite
(Elanus leucurus)
Legal Status
State: Fully Protected
Federal: None
Critical Habitat: N/A
Recovery Planning: N/A
Taxonomy
There are currently two recognized subspecies of white-tailed kite
(Elanus leucurus): E. l. majusculus in North America and E. l. leucurus
in South America. The Integrated Taxonomic Information System
(2011) recognizes Elanus leucurus as a separate species, based on
morphological and behavioral differences (Clark and Banks 1992)
from Elanus caeruleus (black-shouldered kite), which occurs in
southwest Europe, Africa, and South Asia east to China and the Malay
Peninsula. However, until biochemical analyses are conducted on
Elanus kites, the taxonomy will likely remain in flux (Dunk 1995). A
description of the species’ physical characteristics can be found in
Dunk (1995).
Distribution
General
The core of the white-tailed kite’s breeding range in the U.S. is
California, with nearly all areas up to the western Sierra Nevada
foothills and southeast deserts occupied (Dunk 1995). It is common in
the Central Valley of California and along the entire length of the
coast, possibly breeding in more arid regions east of the Sierra Nevada
and Transverse Range (Inyo and eastern Kern Counties), with
documented breeding in Imperial County (Small 1994; Patten et al.
2003), western Riverside County (County of Riverside 2003), and
eastern San Diego County (Unitt et al. 2004). The Coachella, Imperial,
and Mexicali Valleys have records of white-tailed kites mostly from
fall and winter (Patten et al. 2003). In the Sacramento Valley, kite
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White-Tailed Kite (Elanus leucurus)
populations have predominantly increased in irrigated agricultural
areas where the California vole (Microtus californicus) often occurs
(Warner and Rudd 1975). White-tailed kite also breeds in other parts
of North America, such as western Oregon, southwest Washington,
south Texas, and south Florida, as well as Baja California, Mexico, into
Central America, and in South America from Colombia south to
Buenos Aires (Figure SP-B18; Dunk 1995; County of Riverside 2003).
Distribution and Occurrences within the Plan Area
Historical
White-tailed kites were recorded sporadically in the Plan Area
historically (i.e., pre-1990). In 1923, Van Rossem noted a white-tailed
kite flying up and down the Mojave River, near Victorville, San
Bernardino County (Pickwell 1930). A white-tailed kite was recorded
in the Coachella Valley, near Mecca, in 1965, and again in the summer
of 1984 (Patten et al. 2003). In the Imperial Valley, a pair bred in 1975
near Brawley (Patten et al. 2003). Records also exist for Finney Lake
(north of Brawley) from 1984 and 1985 (Patten et al. 2003).
Recent
A number of nesting records from the Imperial Valley indicate that the
white-tailed kite may now be continuously resident there (Patten et al.
2003). In 1993, a pair nested in the valley near the mouth of the New
River and produced at least one young, while two pairs were suspected
of nesting along the New River in 2000: one east of Fig Lagoon and the
other southwest of Brawley (Patten et al. 2003). Also, a pair definitely
nested near the south end of the Salton Sea in 1995 and 1996 (Patten et
al. 2003). At least 12 individuals were recorded during the winter of
1993–1994 in the Imperial Valley (Patten et al. 2003).
Numerous sightings of white-tailed kite for the period of March
through July have also been reported in the eBird database (eBird
2011). White-tailed kite have been observed at the following locations
in the Antelope Valley: Holiday Lake (May 1994 near the community
of Neenach), Piute Ponds (most recently in July 2006 north of
Lancaster), 60th Street East at East Avenue H and East Avenue G (May
1993 in Lancaster), 110th Street East at East Avenue J (May 1996),
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White-Tailed Kite (Elanus leucurus)
and Lake Palmdale (April 2007 in Palmdale). Near Blythe, there are
white-tailed kite records from the Palo Verde Ecological Reserve and a
nearby location (observed on several occasions from April 14 through
July 20, 2011). There are also two white-tailed kite sightings from
Mojave National Preserve (observed in May 1993 and April 2004) and
one from Harper Dry Lake (observed in April 1998). In Inyo County, a
white-tailed kite was observed in March 1998 north of Independence.
Seven additional observations in the Plan Area are from the Salton Sea
area in 1996, 2009, 2010, and 2010 (Dudek 2011).
Natural History
Habitat Requirements
The white-tailed kite is commonly associated with certain types of
agriculture areas (Grinnell and Miller 1944). It also generally occurs
in low-elevation grassland, wetland, oak woodland, low shrub, open
woodlands, or savannah habitats. This species also uses fence rows
and irrigation ditches (with residual vegetation). Riparian areas
adjacent to open space areas are typically used for nesting (County of
Riverside 2003), where kites prefer dense, broad-leafed deciduous
trees for nesting and night roosting (Brown and Amadon 1968). They
also nest in young redwoods and mid-sized Douglas firs in Northern
California. In the Mojave and Sonoran Deserts of southeastern
California, white-tailed kites are associated with riparian, wetland,
and irrigated habitats. Within foraging habitat, the specific plant
associations seem unimportant; vegetation structure and prey
abundance are more important. Rainfall and humidity vary greatly
throughout the range, but areas with extensive winter freezes are
generally avoided. Nest tree/shrub species range from single isolated
trees to trees within relatively large stands and shrubs less than 3
meters (10 feet) tall.
Winter habitat is not substantially different than breeding habitat but
the proximity to trees is not as important. The white-tailed kite is
known to communally roost in the summer, fall, and winter, generally
in small stands of trees, but roosts have also been observed in open
fields on the ground and in orchards (County of Riverside 2003).
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White-Tailed Kite (Elanus leucurus)
Table 1. Habitat Associations for White-Tailed Kite
Land Cover
Type
Grassland,
certain
agriculture
Land
Cover Use
Foraging
Habitat
Designation
Primary
Tree–shrub
Nesting/
roosting
Secondary
Habitat
Parameters
Ungrazed
grasslands,
irrigated pasture,
alfalfa, other
forage crops
Single isolated
trees, trees within
relatively large
stands, and shrubs
Supporting
Information
Direct
observation
surveys
Direct
observation
surveys
________________
Sources: Dunk 1995; Reeves and Smith 2004; Johnson and Horn 2008;
Pandolfino et al. 2011.
Foraging Requirements
Small mammals (prey falling within the 20–70-gram [0.71–2.47
ounces] range) comprise over 95% of white-tailed kite prey. However,
they occasionally take birds, insects, reptiles, and amphibians (County
of Riverside 2003). In California, kites are known to be reliant on
California voles (Microtus californicus) as a prey source, and habitat
quality is largely dependent on abundance and availability of
California voles (Niemela 2007). Lightly grazed or ungrazed fields
generally support larger prey populations and appear preferred by
white-tailed kites (Johnson and Horn 2008; Pandolfino et al. 2011).
White-tailed kites prefer alfalfa, hay, and irrigated pasture agricultural
areas (Reeves and Smith 2004; Pandolfino et al. 2011) while orchard,
vineyards, and most row crops are not preferred (Erichsen et al 1996;
Reeves and Smith 2004; Pandolfino et al. 2011). Wetlands or marshes
where California voles tend to be abundant would also be important
foraging habitat.
Reproduction
White-tailed kites build a platform of sticks in the fork of a tree or tall
bush. Nests are generally not reused in subsequent breeding seasons,
although some reuse has been reported (County of Riverside 2003).
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White-Tailed Kite (Elanus leucurus)
They lay 3 to 6 eggs (mean of 4.1) that are incubated for 30 to 32 days
(Dunk 1995). The young kites fledge at 5 to 6 weeks of age. If prey is
abundant, a second clutch of eggs may be laid. Nest-building occurs
January through August (Dunk 1995). Egg-laying begins in February
and probably peaks in March and April. Peak fledging probably occurs
in May and June (Erichsen 1995), and total dependency on parents as
fledglings is about 1 to 2 months (Dunk 1995). Erichsen et al. (1996)
listed several factors they found important in their study of successful
white-tailed kite nests: 1) Nests are in rows or patches of trees
overlooking low-lying natural vegetation, fallow fields, wet pasture, or
alfalfa; 2) nests are less than 1,500 meters (4,921 feet) from fresh
water; 3) nests are greater than 100 meters (328 feet) from roads;
and 4) nests are within 800 meters (2,625 feet) of natural, fallow, or
riparian vegetation. Niemela (2007) found that land uses surrounding
kite nests had significantly more agriculture, grassland, riparian, and
woodland habitat, and significantly less chaparral habitat than unused
sites. Hawbecker (1942) noted that during the breeding season, kites
seldom forage farther than a 0.5-mile radius from the nest site. In
summary, nest sites are closely associated with foraging habitat that
supports dense rodent populations.
X
X
X
X
X
X
X
X
X
Dec
X
Nov
Aug
X
Oct
July
X
Sep
June
Breeding
X
X
X
X
Post-breeding
dispersal
Communal night
roosting
X X
X
________________
Sources: Dunk 1995; Erichsen 1995.
May
April
March
Feb
Jan
Jan
Table 2. Key Seasonal Periods for the White-Tailed Kite
X
X
Spatial Activity
The white-tailed kite is a primarily non-migratory resident through
most of its breeding range (Erichsen et al. 1996). However, they may be
nomadic during periods of low prey abundance. Dispersal occurs
during the non-breeding season, leading to a temporary range
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White-Tailed Kite (Elanus leucurus)
expansion that includes most of California. Territory size is highly
variable because it is regulated ultimately by prey abundance. Home
range for non-breeders is difficult to determine since communal roosts
may be tens of kilometers away from foraging habitat (Dunk 1995).
Communal night roosting occurs frequently within wooded habitat.
When females are nesting, male kites may attend communal roosts
(Erichsen 1995). Roosting communities may also include newly
fledged birds, as well as non-breeding kites (Wright 1978; Waian and
Stendell 1970). Waian (1973) observed an increase in roost sizes
through fall into winter, reaching a maximum in January and
decreasing in number until March; a great deal of variation was seen
in roosting density; a eucalyptus tree was used by 48 birds, while 40
kites spread out through 20 lemon trees.
Table 3. Movement Distances for the White-Tailed Kite
Type
Territory Size
Natal
Dispersal
Migration
Other
Distance/Area
17–120 ha (42–297 ac)
1.6–25 ha (4–62 ac)
Location of Study
San Diego, CA
Eureka, CA
19–52 ha (47–128 ac)
160 km (99 mi)
Santa Barbara, CA
San Diego, CA
Citation
Henry 1983
Dunk and
Cooper 1994
Waian 1973
Dixon et al.
1957
Unknown
Ecological Relationships
The primary factor known to regulate populations is prey (Stendell
1972; Dunk and Cooper 1994). Availability of nesting and roosting
sites becomes important in areas where prey are not limiting (Dunk
1995). White-tailed kite abundance and nest success is largely tied to
cyclic fluctuations in abundance of its main prey species, the
California vole. However, California vole is not a desert species and
thus may not be a major prey item for white-tailed kites in
southeastern California. White-tailed kites nest in trees and shrubs,
and conservation and proximity of these features to suitable foraging
habitat is important. They also utilize communal night roosts as non-
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White-Tailed Kite (Elanus leucurus)
breeders, recent fledges, and juveniles. White-tailed kites appear to be
sensitive to human disturbance at night roosts (Dunk 1995).
Population Status and Trends
Global: G5, Secure (CDFG 2011)
State: S3, Vulnerable (CDFG 2011)
Once predicted to be headed toward extinction in California due to
habitat loss, shooting, and possibly egg collecting (Pickwell 1930), the
population of white-tailed kite increased dramatically from the 1940s
to early 1980s (Dunk 1995). Increased agricultural irrigation,
agricultural habitat fragmentation, reduced persecution, and the
species’ potential for population growth may have positively
influenced numbers (Eisenmann 1971). A brief decline in the
California population in the mid-1970s corresponded with a drought
and corresponding movements into Oregon (Pruett-Jones et al. 1980).
This species also declined in the Central Valley of California between
1990 and 1993 (Erichsen et al. 1996), but such short-term trends may
simply reflect changes in prey (vole) abundance. Based on breeding
bird survey data, the most significant decline occurred in the Southern
California grassland region from 1982 to 1991, with an annual decline
of about 40% (Dunk 1995).
Threats and Environmental Stressors
The primary factor known to regulate white-tailed kite populations is
prey availability. Factors influencing population trends directly or
indirectly include: 1) conversion of natural or agricultural lands to
urban sprawl or commercial properties, 2) clean farming techniques
that leave few residual vegetation areas for prey, 3) increased
competition for nest sites with other raptors and corvids, 4) drought,
5) increased disturbance at nests, and 6) removal of suitable nesting
habitat (Dunk 1995). Within the Plan Area, the main threats would
include reductions in prey abundance with conversion of agriculture
to non-agricultural uses, particularly when located in proximity to
suitable nesting/roosting habitat. Threats relating to the conversion
of agriculture to non-agricultural uses would also include the removal
of tree windrows that could support nest/roost sites. Changing
agricultural practices also have the potential to reduce prey
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White-Tailed Kite (Elanus leucurus)
availability in the Plan Area, such as the conversion of agriculture that
favors prey species (alfalfa, hay, irrigated pasture) to agriculture that
does not (row crops, orchard, and vineyard). Within the Plan Area, the
reduction of wetlands, a winter forage habitat used by white-tailed
kites (Pandolfino et al. 2011), is not expected to be a threat due to
other legal protection mechanisms.
Conservation and Management Activities
No species-specific conservation or management is known within the
Plan Area. However, according to Sections 3511 and 4700 of the
California Fish and Game Code, which regulate birds and mammals,
respectively, a “fully protected” species may not be taken or possessed
without a permit from the Fish and Game Commission, and “incidental
takes” of these species are not authorized. The fully protected status
would protect active white-tailed kite nests only.
Data Characterization
There are data gaps for white-tailed kite occurrences within the Plan
Area, illustrated by the lack of recorded desert nesting occurrences in
the California Natural Diversity Database. However, there are some
scattered records in books (Birds of the Salton Sea), and eBird has
compiled numerous records based on periodic reporting from
individuals who complete species lists during local birding trips. The
main data gap is the current breeding locations of white-tailed kite in
the Plan Area. Enough information about the foraging, nesting, and
roosting requirements for this species is available, however, so that it
can be covered by the Desert Renewable Energy Conservation Plan.
Management and Monitoring Considerations
Marsh habitat is an important native community for white-tailed kite
foraging, and management practices could maintain various
successional stages of marsh habitat for prey species. Agricultural
management practices could also benefit foraging opportunities for
this species, such as maintaining prey refugia areas and maintaining
beneficial crops. Management of agriculture drains and dikes to
maintain marsh habitat would also benefit prey species for whitetailed kite. Management of grasslands to maintain ungrazed areas
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White-Tailed Kite (Elanus leucurus)
would also benefit prey populations. A small-scale example of
successful management of white-tailed kite occurred in Northern
California where previously grazed grasslands were removed from
grazing. These areas now support large populations of voles and high
densities of wintering white-tailed kites, approximately 10 times the
raptor density they supported prior to management (Dunk 1995).
Conservation of existing trees and shrubs for nesting/roosting and
minimization of human disturbance at known nesting/roosting
locations would also be important considerations.
Goals for monitoring of white-tailed kite might be to first identify
high-quality foraging habitat located near suitable nesting/roosting
habitat (trees and shrubs) and determine whether nesting or
communal roosts are present at these locations. The surrounding
foraging habitat could then have higher management priority for
maintaining high densities of prey species.
Some difficulties are inherent in monitoring a facultatively nomadic
species whose population can fluctuate greatly with rainfall and prey
abundance, and tends to vacate and establish in areas very quickly.
These factors make the choice of the correct unit area for monitoring
efforts difficult. Also, because white-tailed kites roost communally at
sites that can be tens of kilometers away from foraging sites, home
range for non-breeders is difficult to determine (Dunk 1995).
Predicted Species Distribution in Plan Area
There are 877,844 acres of modeled suitable foraging habitat for
white-tailed kite in the Plan Area. Modeled suitable habitat includes
agriculture and grassland vegetation communities throughout the
Plan Area. Appendix C includes specific model parameters and a
figure showing the modeled suitable habitat in the Plan Area.
Literature Cited
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White-Tailed Kite (Elanus leucurus)
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November 21, 2011. http://www.dfg.ca.gov/biogeodata/
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Erichsen, A.L., S.K. Smallwood, A.M. Commandatore, B.W. Wilson, and
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Johnson, M.D., and C.M. Horn. 2008. “Effects of Rotational Grazing on
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Reeves, K.A., and J.R. Smith. 2004. “Survey of Falcons, Kites, Hawks,
and Owls in the Lower Mokelumne River Watershed,
Sacramento and San Joaquin Counties, California.” Accessed
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Stendell, R.C. 1972. The Occurrence, Food Habits, and Nesting Strategy
of White-Tailed Kites in Relation to a Fluctuating Vole
Population. Dissertation. Berkeley, California: University of
California at Berkeley.
Unitt, P., A.E. Klovstad, W.E. Haas, P.J. Mock, et al. 2004. San Diego
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Natural History.
Waian, L.B. 1973. The Behavioral Ecology of the North American WhiteTailed Kite (Elanus leucurus majusculus) of the Santa Barbara
Coastal Plain. Dissertation. Santa Barbara, California:
University of California at Santa Barbara.
Waian, L.B., and R.C. Stendell. 1970. “The White-Tailed Kite in
California with Observations of the Santa Barbara Population.”
California Fish and Game 56:188–198.
Warner, J.S., and R.L. Rudd. 1975. "Hunting by the White-Tailed Kite
(Elanus leucurus)." Condor 77:226–230.
Wright, B.A. 1978. Ecology of the White-Tailed Kite in San Diego
County. Thesis. San Diego State University, San Diego,
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