California Partners in Flight Desert Bird Conservation Plan
Scott's Oriole (Icterus parisorum)
Prepared by: Ron Gartland (Ronald_Gartland@ca.blm.gov)
BLM - California Desert District
22835 Calle San Juan de los Lagos
Moreno Valley, CA 92553-9046
Gartland, R. 2006. Scott's Oriole (Icterus parisorum). 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
No subspecies (Blake 1968, Oberholser 1974).
Not officially listed as Threatened, Endangered, or at risk in any part of its range. "Moderately threatened" on both breeding and wintering grounds because it faces "moderate" habitat loss, has somewhat specialized ecological requirements, and is not particularly widespread in its distribution; threat not considered urgent (Carter and Barker 1993). "Medium" sensitivity to human disturbance, as occurring in three habitat types that are not specifically threatened, and as being fairly common; in terms of conservation and need for further research, species rates "low priority" (Stotz et al. 1993).
HISTORICAL BREEDING DISTRIBUTION:
CURRENT BREEDING DISTRIBUTION:
The California breeding range of Scott's Oriole is north to San Luis Obispo, Kern, Inyo, and Mono counties. Fairly common in the Mojave Desert south to Joshua Tree National Park and west to the north slopes of the San Gabriel and San Bernardino mountains and along the desert slopes and valleys of the San Jacinto, Santa Rosa, Volcan, and Laguna mountains. In Kern County, breeds from eastern slopes of the Sierra Nevada and Tehachapi mountains west into Walker Basin (Flood 2002).
AVERAGE TERRITORY SIZE
Territory size not well studied, sometimes described as large, but probably depends on availability of Yucca spp. or other suitable nesting trees. Large territories described by some authors may be temporary and primarily for mate attraction. Both male and female commonly fly far from nests to obtain food for young, often crossing "territories" of several neighbors; thus likely defend only a small area for mating, nesting, and perhaps some feeding needs (Flood 2002).
TIME OF OCCURRENCE AND SEASONAL MOVEMENTS
Arrival date on breeding grounds:
In southwest U.S., most migrants arrive on the breeding grounds in late March to early April; wide variation in individual migration times apparent, as some birds remain on wintering grounds until late April. In California, migrants are fairly common from mid-March; most breeders are in place by mid-April. Some birds are still migrating through early April, although others have begun nesting by this time (Flood 2002).
Departure date from breeding grounds:
Individuals start departing the breeding grounds mid-July to early August, arriving in wintering areas by late September. By mid-September, most individuals have left U.S. In California, breeders present until mid- to late-July, and migrants common from then through mid-August (Flood 2002).
Spring migration period:
Late March - early April.
Fall migration period:
Mid July - early August.
Extent of wintering in CA:
Small numbers found in wooded canyons on western edge of southern deserts (Garrett and Dunn 1981).
MIGRATION STOPOVER CHARACTERISTICS:
Short to medium distance migrant in much or most of its range (Flood 2002).
Scott's Orioles migrate northward along the Pacific coast of Baja California (more common in fall than spring), but in California they appear to move inland and migrate along desert slopes of mountains, perhaps seeking preferred semiarid habitats (Flood 2002).
The Scott's Oriole probes for insects in low vegetation, on the ground, or in arborescent yuccas and other trees several meters from the ground.
It seems to be an adaptable species with an apparently broad foraging niche (Flood 2002). On both the breeding and wintering grounds, Scott's Orioles mainly feed on insects, supplemented by fruit and nectar (Bent 1958). During the breeding season, this species eats both larval and adult insects. Insect groups include ants and bees (Hymenoptera), moths and butterflies (Lepidoptera) associated with the joshua tree, grasshoppers and crickets (Orthoptera), beetles (Coleoptera), and spiders (Arachnida). Nectar taken from Agaves spp. and possibly from flowering stalks of joshua tree (Yucca brevifolia). Scott's Orioles may eat lizards (Lacertilia) and fruits, mainly cactus and domestic cultivars. During the winter season, Scott's Orioles feed extensively on the ripe fruit of cactus in Baja California (Bent 1958). In central Mexico, occasionally seen hunting at overwintering roosts of monarch butterflies.
Probably obtains necessary water from food. Observations in California showed that Scott's Orioles visited water sources, but did not drink. Observers suggest that Scott's could probably survive without drinking, but do so in extreme high temperatures (Smyth, Coulombe, Miller, Stebbins, Weathers; in Flood 2002).
Breeding habitat is most common in relatively high elevation (up to 3000m) arid environments, particularly desert facing slopes of mountains, piñon-juniper habitat in foothills, and semiarid plains between mountain ranges, where Yucca spp. are common (Bent 1958). In California, the elevation range is from 300 meters in the southern deserts (low elevation desert oases) to 2500 meters in yucca and piñon-pine woodlands, and less common in adjacent dry interior oak woodlands.
Nests are often located on the plant periphery, but with plenty of overhanging vegetation (Smith 1967, Thomas 1975).
Most commonly associated with yucca trees (Yucca spp), but also nest in palm (Washingtonia spp), piñon-pine (Pinus cembroides), and juniper species (Juniperus spp). Some less common nesting substrates are: sycamore (Platanus spp), oak (Quercus spp), cottonwood (Populus spp) in canyons; and records describe nests in boojum (Fouquieria columnaris), elderberry (Sambucus nigra), mango (Mangifera indica), orange (Citrus spp), palo verde (Cercidium floridum), mesquite (Prosopis spp), and olive trees (Olea europaea).
HEIGHT OF NEST:
Generally 1.5-3 meters (sample average = 2.2) above ground, although sometimes higher. Nest height could be as low as 1m or as high as 6.5m (L. Kiff in Flood 2002).
HEIGHT OF PLANT:
Generally 2-4.5 meters (sample average = 3.12) (Flood 2002).
Typically, nest is woven into or around and partially suspended from overhanging leaves at the top of a yucca tree, attached at one or more sides. Most nests reasonably well concealed among plant leaves, with usually less than fifty percent of the nest visible when standing in front of it.
Typically a semipensile basket woven together with fibers stripped from dead Yucca spp. leaves. Lining usually consists of soft grasses and other "cotton-like" plant fibers, such as hairs or fuzz covering seeds (Flood 2002).
Usually sings from a conspicuous location, such as a yucca or other tree (Oberholser 1974). Males sing in flight as approaching and leaving the nest (Miller and Stebbins 1964) and when perched near nest site while female is nest-building, incubating, or brooding. Females will sing from the nest and while perched (Flood 2002). Both males and females call whenever a predator, intruder, or human observer is spotted. This call will be loud and rapid when danger is near the nest site, lessening when disturbance is less severe. Male Scott's Orioles often sing directly to the female during and after pairing, which may help the pair remain in contact and facilitate pair-bond maintenance (Rising and Flood 1998).
Precopulatory displays only observed on or near the ground (Flood 2002). Females will give a high-pitched twittering call during a precopulatory solicitation display similar to other orioles, where she flutters lowered, partially extended, wings in front of the male.In breeding areas, several males may be heard singing at the same time, suggesting vocal duels and use of song for territorial defense (Rising and Flood 1998). After displaying to a female, a courting male was observed to fly to several points and sing, as though marking territory (Dixon 1960). Continuous singing throughout the summer may support the song's role in territorial defense and increasing mating opportunities given the species' extended breeding season (Flood 2002).
Agonistic displays involve close passes, in-flight chases, or attacks where
actual contact is made in the air, on perch, or on the ground, although territorial
interactions are rare and occur primarily when conspecific intruders closely
approach a nest (Flood 2002).
Seasonally monogamous, unless a mate disappears or dies. Occasionally, a pair bond will reunite in following seasons, but most individuals find new mates (Flood 2002).
1-5 eggs, 3 most common (Texas). 4-5 egg clutches may be more common in other parts of species range. Clutch size may decline for third nests.
Only female incubates.
Most females begin incubation after second egg (usually penultimate, laying 1 egg/day). Time between laying of last egg and first hatching ranges from 11-15 days (sample average = 13) and incubation period decreases with increased clutch size, suggesting that effective incubation begins after second egg is laid.
DEVELOPMENT AT HATCHING:
Average time from first egg hatched to first fledgling is 12 days (range = 9-15 days).
Only the female broods nestlings, with the time spent brooding decreasing as nestlings get older. The male will occasionally bring food to the brooding female. Both males and females provision nestlings, splitting the number of feeding trips virtually equal. Both parents defend the nest and remove fecal sacs.
POST BREEDING SOCIAL BEHAVIOR:
Not well studied. Families disappear from vicinity of nests within 48 hours and are difficult to locate after that. Females must cease caring for fledglings from the first nests as early as 2 weeks after fledging and from second nests almost immediately. Males have been observed feeding fledglings while the female incubated a new clutch (Flood 2002).
POST FLEDGING BIOLOGY OF OFFSPRING:
Young apparently heavily dependent on parents for 2 -3 weeks following fledging, but frequency of renesting suggests they must be able to care for themselves reasonably soon after that (Flood 2002).
NUMBER OF BROODS:
Single- or double-brooding with some pairs attempting a third brood. Early nesters are able to nest a second (and possibly third) time during one breeding season. In Texas, Flood observed pairs beginning second and third broods and/or renesting after failure in late July (Flood 2002).
Both Brown-headed and Bronzed Cowbird instances of parasitism observed in Mexico, Arizona, and Texas. No data found for California.
ADJACENT LAND USE:
DEMOGRAPHY AND POPULATION TRENDS:
Bent, A. C. 1958. Life histories of North American blackbirds, orioles, tanagers, and allies. U.S. Natl. Mus. Bull. 211.
Blake, E. R. 1968. Family Icteridae. Pp. 138-202 in Check-list of birds of the world. Vol. 14 (R.A. Paynter, Jr., ed.). Mus. Comp. Zool., Cambridge, MA.
Carter, M. F. and K. Barker. 1993. An interactive database for setting conservation priorities for western Neotropical migrants. Pp. 120-144 in Status and management of Neotropical migratory birds (D. M. Finch and P. W. Stangel, eds.). Gen. Tech. Rep. RM-229, U.S. Dep Agric., Forest Service, Fort Collins, CO.
Dixon, K. L. 1960. A courtship display of Scott's Oriole. Auk 77: 348-349.
Flood, N. J. 2002. Scott's Oriole (Icterus parisorum). In The Birds of North America, No. 608 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Garrett, K. and J. Dunn. 1981. Birds of southern California: status and distribution. Los Angeles Audubon Soc., Los Angeles, CA.
Miller, A. H. and R. C. Stebbins. 1964. The lives of desert animals of Joshua Tree National Monument. Univ. of California Press, Berkeley.
Oberholser, H. C. 1974. The birdlife of Texas. Vol. 2. Univ. of Texas Press, Austin.
Rising, J. D. and N. J. Flood. 1998. The Baltimore Oriole (Icterus galbula).
In The birds of North America, no. 384 (A. Poole and F. Gill, eds.). The Birds
of North America, Inc., Philadelphia, PA.
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