California Partners in Flight Desert Bird Conservation Plan
Lucy's Warbler (Vermivora luciae)
Photo by Martin Meyers
Prepared by: Christopher D. Otahal (email@example.com)
21 Vineyard Court
10845 Rancho Bernardo Road
Hollister, CA 95023
Otahal, C.D. 2006. Lucy's Warbler (Vermivora luciae). In The Draft Desert Bird Conservation Plan: a strategy for reversing the decline of desert-associated birds in California. California Partners in Flight. http://www.prbo.org/calpif/htmldocs/desert.html
The Lucy's Warbler is a monotypic species (Johnson et al. 1997) with no geographic variation described (Dunn and Garrett 1997).
The Lucy's Warbler is not listed as threatened or endangered and there are no special conservation measures proposed either at the federal or state level (Johnson et al. 1997). However, Lucy's Warbler appears on the California Species of Concern List (2003), United States Fish and Wildlife Service Migratory Nongame Birds of Management Concern list (1995), Partners in Flight Watch List, and the Audubon Watch List (2002).
HISTORICAL BREEDING DISTRIBUTION:
Little information exists regarding the historical distribution of Lucy's Warbler (Johnson et al. 1997). Loss of riparian, cottonwood (Populus sp.) and willow (Salix sp.) throughout the southwestern US may have diminished or extirpated local populations (Dunn and Garrett 1997, Johnson et al. 1997). In the 1940's, Lucy's Warbler was said to occur occasionally in the Imperial and Coachella Valleys in California, where they may have bred formally (Grinnell and Miller 1944). In California, "formerly common, but currently (due to habitat destruction) only locally fairly common" (Small 1994).
Lucy's Warbler may be expanding its range in some areas. Populations appear
to be expanding in newly created saltcedar (Tamarix ramossisima) habitat
along the Colorado River in the Grand Canyon, Arizona (Johnson et al. 1997).
Lucy's Warbler appears to have occupied its present range in New Mexico only
since the 1920's (Hubbard 1978, Dunn and Garrett 1997). Lucy's Warbler colonized
San Diego County, California in 1900, but is still rare (a few dozen pairs or
less). It is confirmed nesting at only one site: the mesquite bosques in the
center of Borrego Valley, California (Unitt 2004). However, Johnson et al. (1997)
cautions that it is difficult to determine which recent records are due to range
increase or simply increased surveillance by additional workers in remote western
CURRENT BREEDING DISTRIBUTION:
Lucy's Warbler breeds from southeastern California, southern Nevada, and Utah south to southern Arizona, northern Mexico, and extreme western Texas (DeGraaf and Rappole 1995). This species breeds in southeastern California mainly along the lower Colorado River, but locally north to Death Valley National Monument and west to Morongo and Borrego Valleys (Dunn and Garrett 1997). Lucy's Warbler may also breed in Chihuahua, Mexico, adjacent to the Rio Grande Valley of western Texas (National Geographic Society 1987).
Lucy's Warbler winters mainly in a narrow band along the Pacific Slope and adjacent interior of Mexico from southern Sonora and northern Jalisco south to Gurerrero (Johnson et al. 1997) and in smaller numbers to Oaxaca (Bent 1953). Lucy's Warbler is a rare winter visitor along the California coast from central California south to San Diego County as well as along the Rio Grande in the Big Bend region of Texas and southern Arizona (Johnson et al. 1997).
AVERAGE TERRITORY SIZE
Lucy's Warbler may nest in very dense colonies. For example, Johnson et al. (1981) reported pairs near Phoenix, Arizona were spaced as closely as 30 meters in closed canopy bosques. In a desert wash near Tucson, Arizona, nests were spaced 200 meters apart. On a second mesquite site near Tucson, Arizona, 11 pairs on an 11.2 hectare plot were reported (Johnson et al. 1997). Grinnell (1914) reported on a site where Lucy's Warblers were confined to a narrow belt of mesquite along the Colorado River near Blythe, California. The nests at this site were uniformly spaced to occupy strips of 180 meters in length.
TIME OF OCCURRENCE AND SEASONAL MOVEMENTS
Arrival date on breeding grounds
Lucy's Warblers arrive on their breeding grounds in southwestern Arizona as early as 7 March and southeastern Arizona by 10-11 March (Phillips et al. 1964). Lucy's Warblers arrive in mid-March in San Diego County, California and stay through early June (Unitt 2004).
Departure date from breeding grounds
Numbers are greatly diminished in Arizona by late June and are almost entirely gone by late July or early August. Early departure from the breeding grounds perhaps helps to evade much of the summer heat, but further investigation is warranted (Johnson et al. 1997). However, a few birds may linger in southeastern Arizona through early September (Rosenberg et al. 1991).
Spring migration period
Spring migration is not well understood since this species is rarely encountered in spring away from breeding and wintering grounds (Dunn and Garrett 1997). Lucy's Warbler arrives on the breeding grounds earlier than most migrant species (Johnson et al. 1997) beginning about 10 March on the lower Colorado River to about 20-25 March in northern breeding localities. En mass arrival of birds in March coincides with the leafing out of mesquites in the area.
Fall migration period
Lucy's Warblers begin dispersing away from breeding localities by late July or early August, with most birds gone by early September (Dunn and Garrett 1997). This species leaves the breeding grounds earlier than most migratory species, despite an apparent abundance of insects during midsummer. However, early departure from the breeding grounds may allow Lucy's Warbler to evade much of the extremes of summer heat (Johnson et al. 1997). This species is an annual fall migrant to coastal California, especially from Santa Barbara County south, with most records being from late August to early November (Dunn and Garrett 1997).
MIGRATION STOPOVER CHARACTERISTICS:
Little is known regarding migration stopover characteristics (Dunn and Garrett 1997, Johnson et al. 1997). Lucy's Warbler is a temperate, complete short-distance migrant, perhaps making much or all of its spring flight without stopover (Johnson et al. 1997). This species arrives abruptly in numbers on the breeding grounds, most arriving within a 4-5 day period (Gilman 1909, Rosenberg et al. 1991), with males arriving before females (Coues 1878).
Lucy's Warbler is a foliage gleaner from top of canopy to ground level (Johnson et al. 1997) and often focuses on flower clusters (Bent 1953).
The diet of the Lucy's Warbler is almost entirely of insects (Johnson et al. 1997) and the species of insect consumed varies with season (Moody 1970). This species feeds on a variety of arthropods including spiders (Araneae), true bugs (Hemiptera), leafhoppers (Homoptera), beetles (Coleoptera), flies (Diptera), moth larvae (Lepidoptera), wasps (Hymenoptera), biting lice (Mallophaga), and thrips (Thysanoptera) (Moody 1970, Rosenberg et al. 1991). One study recorded large quantities of leafhoppers, known exclusively from tamarisk, in the stomachs of Lucy's Warblers in the Grand Canyon, Arizona (Stevens 1985, Yard 1996).
One Lucy's Warbler was recorded drinking at a spring in oaks at 1,280 meters in southeast Arizona (Smith 1908).
Lucy's Warbler breeds mainly in thickets of mesquite (Prosopis spp.) bosques, mainly honey mesquite (Prosopis glandulosa) but also screwbean mesquite (Prosopis pubescens), and frequently along watercourses or near ponds that have willows (Salix spp.) and cottonwoods (Populus spp.). However, Lucy's Warblers tend to shun mature cottonwood-willow riparian associations (Dunn and Garrett 1997) but will occasionally nest in lowland cottonwood-willow riparian gallery forests (Johnson et al. 1997) and less often in mid-elevation sycamore-ash-live oak (Platanus-Faxinus-Quercus) associations (Johnson et al. 1997). This species ranges into sparser thorn-scrub of palo verde (Cercidium spp. ), ironwood (Olneya tesota), and catsclaw acacia (Acacia greggii) where such habitat borders stands of mesquite (Dunn and Garrett 1997). Lucy's Warbler has also recently begun breeding in tamarisk (Tamarix ramossisima) forests in the Grand Canyon region of Arizona (Johnson et al. 1997).
Grinnell (1914) in (Bent 1953) referring to the Colorado Valley states: "On
the California side, both at Riverside Mountain and above Blythe, Lucy's Warblers
were numerous, and very closely confined to the narrow belt of mesquite. The
birds foraged out to a limited extent from the mesquite towards the river into
arroweed (Tessaria sericea) and willows, and away from the river at the
mouths of washes into the ironwoods and palo verdes. But the metropolis was
always most emphatically the mesquites."
Lucy's Warbler is the only cavity nesting warbler in western US and 1 of only 2 in North America (Johnson et al. 1997). Lucy's Warbler generally places nests in four types of cavities: natural cavities in trees (usually mesquite) where the entrance is in a sheltered spot; under loose bark; in abandoned woodpecker holes (especially those of Gila Woodpecker (Melanerpes uropygialis) in saguaros [Carnegiea gigantean] or other trees); and in deserted Verdin (Auriparus flaviceps) nests. Lucy's Warbler occasionally nests in holes in banks, in soap tree yucca leaves (Yucca elata), elderberry (Sambucus mexicana), sycamore (Platanus spp.), or willow (DeGraaf and Rappole 1995). Lucy's Warbler rarely nests in burrows or depressions in river banks, rocky crevices, deserted thrasher (Toxostoma sp.) and Cliff Swallow (Hirundo pyrrhonota) nests, "pseudocavity" evacuated in mass of debris in tamarisk, or forks in small branches (Johnson et al. 1997).
HEIGHT OF NEST:
Nest heights range from 0.6-6 m above ground and occasionally up to 12.2 m (Bailey 1904, Harrison 1979).
DIAMETER OF NEST PLANT:
In xeric riparian habitats of the lower Colorado River valley, the average diameter at ground height of Lucy's Warbler nest substrate was 82.5 cm. (McCreedy et al. 2005).
DOMINANT PLANT SPECIES IN CANOPY:
Lucy's Warbler usually nests in close association with riparian mesquite trees and shrubs in bosques including acacia (Acacia spp.), hackberry (Celtis spp.), and elderberry and rarely in palo verde and ironwood uplands. Also commonly breeds in recently introduced tamarisk (Johnson et al. 1997).
Lowland riparian breeding habitat includes mesquite and willow thickets, cottonwood-mesquite,
cottonwood-willow gallery forests, cottonwoods, willows, and mid-elevational
ash-walnut-sycamore-live oak (Fraxinus-Juglans-Platanus-Quercus) associations,
and occasionally higher elevation oak-sycamore-alder (Quercus-Platanus-Alnus)
communities surrounded by ponderosa pine (Pinus ponderosa) (Johnson et
DISTANCE TO WATER
Lucy's Warbler usually nests in association with riparian areas. May nest in willows and arrowweed close to a river, and less often in palo verde and ironwood in desert uplands (Johnson et al. 1997).
Lucy's Warbler nests are small well woven nests with a course exterior, lined with soft material such as fur, feathers and plant fibers (Johnson et al. 1997).
BREEDING TERRITORY SIZE AND DENSITY:
Lucy's Warbler breeds in some of the densest concentrations of any non-colonial nesting species in North America. The highest reported nesting density for this species was 94.1/40 hectare in Cardenas Marsh on the Colorado River in the Grand Canyon, Arizona (Johnson et al. 1997). The density of nests varies with habitat type. On the Colorado River in Grand Canyon, nesting densities were 228.8 pairs/40 ha in mesquite dominated old-high water zone, while nesting densities in tamarisk was 200 pairs/40 ha (Brown 1989). In central Arizona, 109-125 pairs/40 ha was reported from a Gooding willow-tamarisk riparian plot while a palo verde-saguaro desert scrub plot had only 11-15 pairs/40 ha (Szaro and Jakle 1982). Densities in desert washes may be somewhat lower. In Amargosa Canyon, California, nesting territories in a cottonwood-willow forest was 0.12/ha whereas in tamarisk densities were 0.47/ha (McCreedy 2006b). At Chemehuevi Wash, California, nest densities (in palo verde) in a low off-road vehicle use area were 0.08/ha while that in a high off-road vehicle use area was 0.43/ha (McCreedy 2006a).
INITIATION OF NESTING
It is not known which member of the pair selects the nest site; however, males arrive first and begin immediate persistent song. Apparently only the female builds the nest, but the male will often accompany her while she flies from tree to tree with nesting material and exhibits mate-guarding while she builds. Along the Gila River in south central and southwestern Arizona, the earliest completed nest date reported was 10 April and the latest was 15 May, while others have reported completion dates as late as 27 June (Johnson et al. 1997).
Males use song to advertise territorial occupancy and to maintain territorial boundaries. Males usually sing for a few hours in the morning, but will sing throughout the day at the height of the breeding season. Males usually sing at the top of larger bushes or trees and actively move around while singing or between songs. When two males meet at territorial boundaries, they sing rapidly and persistently before making physical contact. Males establish territories by patrolling the perimeter while singing, giving threat displays (raising crown and flicking tail), and engaging in physical confrontation and fights. Males may sing in response to intrusion; the female also chips in rapid succession when the nest is approached by humans. Males pursue females by spreading wings to show rump patch and sometimes erecting their crown (Johnson et al. 1997).
Appears to be monogamous.
Laying of first to last egg 4 days. Usually 4 or 5 eggs are laid (range 3-7) (Johnson et al. 1997).
Incubation is poorly documented in Lucy's Warbler. Incubation is carried out by the female, possibly with the help of the male (Baicich and Harrison 1997), but the role of the male is not well documented.
The incubation period is unknown (Bent 1953), but has been estimated at 12 days by Brown (1994). No information on brooding behavior was found (Johnson et al. 1997).
DEVELOPMENT AT HATCHING:
Young are altricial, born without down feathers and with eyes closed. Apparently, hatching is asynchronous, but the eggs may hatch throughout day (Johnson et al. 1997).
The nestling period is estimated at 11 days after hatching (Johnson et al. 1997).
Little is known about Lucy's Warbler parental care. There is no information on diet or feeding rates at the nest. There is no data on which parent cares for the young (Johnson et al. 1997); however, Baicich and Harrison (1997) indicate that both parents tend the young.
POST FLEDGING BIOLOGY OF OFFSPRING:
Little is known regarding the fledgling biology of the offspring and there are no data on dispersal from the natal site or breeding site (Johnson et al. 1997).
NUMBER OF BROODS:
It is probable that Lucy's Warbler has at least two broods per year (Bent 1953).
Despite being a cavity nester, brood parasitism by Brown-headed Cowbird (Molathrus ater) may also have affected some already dwindling local populations of Lucy's Warbler (Johnson et al. 1997).
This species usually nests below 1,000 meters, ranging from 60 meters and occasionally up to 1,775 meters (Johnson et al. 1997).
Lucy's Warbler nests have been destroyed and/or eggs eaten by wood rats (Neotoma spp.) and snakes (Howard 1899) as well as lizards and Gila Woodpeckers (Dawson 1923, Bent 1939).
DEMOGRAPHY AND POPULATION TRENDS:
The longest banding record for this species is 5 years 10 months (Klimkiewicz and Futcher 1989).
Lucy's Warbler may breed in the first breeding season after hatching, but this is not well documented (Johnson et al. 1997). In xeric riparian habitats of the lower Colorado River valley, Lucy's Warblers achieved a 50% nest success at Chemehuevi Wash, California in 2004 (McCreedy et al. 2005) and the success rate went up to 100% in 2005 (McCreedy 2006a). On the Amargosa River, California, a nest success rate of 56% was achieved in 2005 (McCreedy 2006b). There is no information on lifetime reproductive success (Johnson et al. 1997).
Lucy's Warbler population numbers may be diminishing throughout its breeding
range because of riparian habitat loss and mesquite cutting throughout the southwestern
United States. However, the population seems to be increasing and expanding
to new locations in some areas. Some population fluctuations are unexplained
and need further investigation (Johnson et al. 1997).
1. Riparian ecosystems have been greatly reduced locally throughout much of the southwestern United States, extirpating many breeding populations of Lucy's Warbler. Degradation and loss of riparian mesquite habitat is generally detrimental to this species and has extirpated some local populations, although current habitat losses do not appear to present a threat to the species as a whole (Johnson et al. 1997). Based on a few sightings elsewhere in San Diego County, Lucy's Warbler could colonize additional stands of mesquite. However, the future of bosques in Borrego Valley where they now occur is endangered by the continued pumping of groundwater (Unitt 2004).
2. Since Lucy's Warbler also breeds in cottonwood and willow, degradation and destruction of southwestern riparian habitats has had a heavy impact on this species. No direct management actions specifically targeting this warbler have been taken, but generalized riparian restoration efforts should eventually benefit this species. However, in a few instances, population increases have been noted in tamarisk thickets along the Colorado River in the Grand Canyon, Arizona (Johnson et al. 1997).
3. Unlike many cavity-nesting species, Lucy's Warblers will not use nest boxes (Johnson et al. 1997).
Bell's Vireo (Vireo bellii) commonly occurs with Lucy's Warbler (Johnson et al. 1997).
MONITORING METHODS AND RESEARCH NEEDS:
Males respond readily to playback recordings during breeding season facilitating censusing (Johnson et al. 1997).
Aside from the review of Bent, a complete life history study has never been
conducted for this species. Complete information is lacking on this species'
breeding ecology (e.g., mate selection and copulation, nest building, incubation,
and parental care) as well as information on demographics, causes of population
fluctuations, and general life history and ecology. The following research needs
are taken from Johnson et al. 1997.
1. Investigate general natural history and ecological traits such as song types and vocalization patterns, and breeding/nesting phenology.
2. Verify current life history assumptions including monogamy, only males sing, only females build nests, only female incubates.
3. Examine the possible breeding in Chihuahua, Mexico
4. Determine basic migration information including whether they are nocturnal
or diurnal migrants, whether they migrate singly or in flocks, the speed of
5. Investigate wintering grounds needs, especially regarding the recently discovered (1990's) wintering in the Big Bend region of Texas.
6. Expand Christmas Bird Counts into western Mexico.
7. Establish standardized population monitoring.
8. Expand existing banding programs.
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