California Partners in Flight-Bird Conservation Plan
Draft Species Account
Authors - Mary K. Chase and Mark D. Reynolds
SPECIES: Yellow-billed Magpie (Pica nuttalli)
SUBSPECIES STATUS: No subspecific variation.
MANAGEMENT STATUS: No official status.
I. range map: Also see map in Reynolds (1995).
A. Expert opinion: See Reynolds (1995).
B. Point count (singing individual encountered on 2 or more different days of census-at least one week apart): See CalPIF maps/database.
C. Mist netting (female with brood patch, female with eggs in oviduct, juvenile with no skull ossification before 1 August): See CalPIF maps/database.
D. Nest searching: See CalPIF maps/database.
E. Spot mapping: See CalPIF maps/database.
F. Area search: See CalPIF maps/database.
G. Breeding Bird Atlas: In eastern Contra Costa County, confirmed as a breeder in five atlas blocks and possible breeder in an additional two clocks (Contra Costa County Bird Atlas, http://www.flyingemu.com/ccosta/ybma.html). Not known as a breeder in San Diego County (San Diego County Bird Atlas, (http://www.sdnhm.org/research/birdatlas/).
H. BBS route: http://www.mbr-pwrc.usgs.gov/bbs/bbs2001.html
I. Other/Local opinion: Recent breeding record near Fresno (Kreitinger pers. comm.).
ECOLOGY:
I. Average territory size: Territories are poorly defined, and home ranges
overlap considerably. Average home range of radio-tagged individuals was 22.8
ha (SD = 30.4, range = 0.05-118.1 ha, n=22 individuals) in the breeding season
and 33.1 ha (SD = 29.9, range = 0.73-105.5, n = 18 0 in the non-breeding season
(Reynolds 1990, 1995). Within home ranges, pairs defend a small core area of
about 1.2 ha (range 0.6-1.9 ha, n = 13; Verbeek 1973).
II. Time of occurrence and seasonal movements.
A. Arrival date on breeding grounds: Non-migratory; generally stays near breeding grounds.
B. Departure date from breeding grounds: Non-migratory. Non-breeders may wander in flocks up to 3.5 km from nesting areas, especially in summer (Jul-Sep; Verbeek 1973, Reynolds 1995).
C. Spring migration period: N/A
D. Fall migration period: N/A
III. Extent of wintering in CA: Entirely within CA.
IV. Migration stop-over needs/characteristics: N/A
A. Stop-over period: N/A
B. Habitat use: N/A
C. Routes: N/A
V. Nest type: Extremely large, globe-shaped, domed bowl. About 0.9 m in diameter
(Harrison 1979).
VI. Foraging strategy: Generally feeds on ground in flocks; picks up items
from surface of ground or just below. Also chases ground-prey, turns over cow
pies, flicks litter with bill, caches acorns and flycatches. Caches food and
recovers it within days.
VII. Displays: Tree-topping display: sitting conspicuously in treetop, associated
with territory establishment and advertisement. Parallel Walk: two agonistic
neighbors walk side-by-side along territorial boundary. Tail-up display: holding
tail vertically for many seconds, often during parallel walk. Wing-flicking
display: wings flicked open and closed, appeasement display. Circling: male
walks around female partner with fluffed feathers, calling and flicking and
quivering wings, performed in days before first egg is laid. Courtship-begging
display: performed by female to beg food from male after egg-laying begins,
flapping wings and high-pitched whining call.
VIII. Social Organization:
A. Typical breeding densities: Density uneven and patchy, home ranges not evenly distributed in suitable habitat. Nests are located in a loosely colonial distribution; colonies contain 3-30 nests. In the area of the Hastings Natural History Reservation, Monterey County, there were about 30 active nests on 500 ha (Reynolds 1995).
B. Mating system: Socially monogamous with long-term pair bonds. Some extrapair courtship and copulation occurs (Verbeek 1973, Birkhead et al. 1992).
C. Delayed breeding (where are immature birds? Possible 'floaters'.): After independence from parents (by about 50 days after hatching), young birds join large flocks with other non-breeders. These young stay with flocks until December or January when the majority appear to disperse to other areas. Young birds often breed in the first season after hatching (as second-year birds; Reynolds 1995).
D. Post fledging biology of offspring: Young are fed by parents until around 50 days of age. Several days after fledging, young may fly to neighboring areas and form "crèches" with fledglings from other nests. Young may follow parents to foraging areas 10-14 days after fledging.
E. Post breeding social behavior (mixed species flocks, or simply migrate away?): Breeders typically remain in vicinity of breeding home range. Non-breeders may wander in large flocks. Will forage on ground near other species e.g. European Starling, Northern Flicker, Western Meadowlark, Brewer's Blackbird, Red-winged Blackbird.
IX. Clutch size: Five to 7 eggs, usually 6 or 7.
X. Incubating sex: Female.
XI. Incubation period: Eggs hatch 16-18 days after beginning of incubation.
XII. Nestling period: Young leave nest about 30 days after hatching.
XIII. Development at hatching: Altrcial and naked.
XIV. Number of broods: Only one brood per season, but will renest if first nest fails early in the season (Reynolds 1995).
XV. Who tends the young: Brooding by female only. Feeding by both parents.
XVI. Diet:
A. Major food items (by season): In general, mostly ground-dwelling invertebrates but also grain, acorns, carrion, and small mammals (references in Reynolds 1995). Breeding season: feeds wide variety of insects to nestlings (62 different families) with consistent use of certain orders (Lepidoptera, Orthoptera) and fluctuating use of others. As soil dries and summer progresses, eats many grasshoppers among other invertebrates. In fall, eats acorns, coffeeberry fruits and poison oak fruits. Also small amounts of domestic crops (e.g. wheat, oats). Carrion eaten largely in winter and spring. May depredate bird nests.
B. Drinking: Drinks from open water sources such as puddles, ponds and cattle troughs.
XVII. Wintering ground needs and distribution: Similar to breeding season.
A. Arrival date on breeding grounds: Non-migratory; generally stays near breeding grounds.
B. Departure date from breeding grounds: Non-migratory. Non-breeders may wander in flocks up to 3.5 km from nesting areas, especially in summer (Jul-Sep; Verbeek 1973, Reynolds 1995).
C. Spring migration period: N/A
D. Fall migration period: N/A
BREEDING HABITAT AND NEST SITE CHARACTERISTICS:
I. Overview of breeding habitat: Oak savanna, where large trees are found within large expanses of open ground. Especially valley floors, gentle slopes and open park-like areas, including along stream courses. Grasslands, pasture, or cultivated fields needed for foraging. NB: Very abundant in sub-urban Sacramento and Davis - nesting in oaks and introduced trees.
II. Nest Site.
A. Substrate (species): Large trees, especially oak trees (valley oak, Quercus lobata; blue oak, Q. douglasii; coast live oak, Q. agrifolia) and in mistletoe (Phoradendron villosum) clumps. Valley oaks and coast live oaks used for over 70% of nesting attempts in one study (Reynolds 1995). Also frequently nest in western sycamore (Platanus racemosa), black cottonwood (Populus trichocarpa), Fremont cottonwood (P. fremontii). Occasionally uses Monterey pine (Pinus radiata), gray pine (P. sabiniana), Monterey Cyprus (Cupressus macrocarpa) and willow (Salix spp.) and introduced species such as black locust (Robinia viscosa), blue gum (Eucalyptus globulus), commercial fruit trees (e.g., walnuts).
B. Height of nest: Averages 14.2 m at Hastings Natural History Reservation (SD = 4.7, n = 67; Reynolds 1990, 1995).
C. Height of plant: Average canopy height of nest trees at Hastings NHR was 16.6 m (SD = 4.3, n = 64; Reynolds 1990, 1995).
D. Nest concealment: No information.
III. Vegetation surrounding the nest
A. Canopy cover: Nests within canopy; canopy cover around nest often 100%.
B. Dominant plant species in canopy: Nest placed in canopy of nest tree (see species above).
C. Average shrub cover: No info.
D. Dominant shrub species: No info.
E. Average forb cover: No info.
F. Dominant forb species: No info.
G. Ground cover: No info.
H. Slope: No info.
I. Aspect: No info.
J. Tree DBH: Average DBH for nest trees at Hastings NHR was 91.3 cm (SD = 42.1, n = 64; Reynolds 1990, 1995).
K. Snags: No info.
L. Distance to water: Permanent water (natural or stock ponds) generally within one km of nest.
M. Other: Nests often located at end of vertical or horizontal branch devoid of side limbs.
IV. Landscape factors
A. Elevation: No quantitative data. Habitat occurs mainly on the floor of the Central Valley and in the adjacent lower foothills of the Sierras and in valleys among Coast Ranges; generally below 3000 ft elevation.
B. Fragmentation: Extensive fragmentation and degradation of habitat has occurred and populations responses have varied geographically. Breeding populations in the Salinas Valley, Monterey County, and Santa Clara County appear to have declined or disappeared due to fragmentation. However, populations in fragmented areas near Sacramento and Davis have persisted (Reynolds 1995).
C. Patch size: No info.
D. Disturbance (natural or managed): Populations may have been lost due to housing and agricultural development in oak savanna habitat. Effects of grazing or fire in oak savanna unknown. Generally thrives in grazed landscape, provided nesting habitat available. Direct persecution (poisoning, shooting, harassing) has decimated populations.
E. Adjacent land use: Little info. Breeding populations can be extirpated as a side-effect of rodent poisoning on adjacent lands (Reynolds 1995).
SPECIAL FACTORS:
I. Brood parasitism: No evidence of intra- or inter-specific brood parasitism (no parasitism by Brown-headed Cowbirds in >600 egg sets of breeding attempts (Reynolds 1995).
II. Dietary: Starvation in a major cause of nesting mortality, thus food supplies
likely influence occurrence and population growth. Reynolds (1995) suggests
that food availability during the breeding season and long summer drought is
the most important regulator of populations.
III. Sensitivity to human-induced disturbance: Direct persecution (poisoning,
shooting, harassing) has decimated populations.Young will fledge prematurely
if nests are disturbed and capture of adults and young and close monitoring
on nests make birds more wary of humans (Reynolds 1995).
IV. Pesticide use: Secondary and incidental poisoning by compound 1080 used
in ground squirrel control programs has been documented, resulting in the extirpation
of a breeding colony (Koenig and Reynolds 1987). Population declines in the
1800s linked to poisoning campaigns (Linsdale 1937).
V. Predators: Few direct observations. Red-tailed Hawks and Golden Eagles take
nestlings and fledglings. Predation on eggs also occurs but predators not identified.
Other known or likely predators include Prairie and Peregrine Falcons, Northern
Goshawks, Cooper's Hawks, Great-horned Owls, Bobcats, Long-tailed Weasels, and
Gopher Snakes. Population-level effects of predation are unknown.
VI. Exotic species invasion/encroachment: No info.
POPULATION TREND:
BBS results for 1966-2001 suggest a fairly stable population in California as
a whole, as well as in the Central Valley and California Foothills regions (Sauer
et al. 2002). Reynolds (1995) estimated the minimum total population size for
Yellow-billed Magpies to be 25,000-50,000 breeding pairs. A recent estimate
of overall population size based on extrapolation from BBS data was 180,000
individuals, which would make Yellow-billed Magpie the least abundant of California's
endemic or near-endemic birds (P. Blancher pers. comm.).
DEMOGRAPHICS:
I. Age and sex ratios: Breeding populations made up mainly of birds of 3 years
old or more, but 20% of known age breeders in the Hastings NHR populations were
second-year birds (Reynolds 1995). No evidence for deviation from 1:1 sex ratio.
II. Productivity measure(s): In upper Carmel Valley, about 65% of eggs laid
hatch and about 70% of chicks hatched survive to fledging (Reynolds 1995). Of
219 nests monitored, 62.6% were successful in producing at least 1 young. Most
successful nests produce 2-3 fledglings (mean = 2.39, SD = 1.2). Hatching success
varies among years and starvation is a major cause of chick mortality. No more
than one brood produced per year. Birds will re-nest after nest failure if failure
occurs early in the breeding season; re-nesting takes place in a refurbished
existing nest. Lifetime reproductive success uncertain due to long life span,
but available data shows 1.9 young (SD = 1.8, n = 18) produced by birds breeding
for only one season and up to 8.8 young (SD = 0.7, n = 8) for birds breeding
for up to 4 seasons.
III. Survivorship: Apparent annual survivorship of breeding adults is about
70% (75.5% for males and 62.7% for females; Reynolds 1995). Juvenile survivorship
unknown due to apparently high rates of natal dispersal (only 3% of young fledged
recruited into their natal breeding colony; Reynolds 1995).
IV. Dispersal: Of 341 birds banded in their hatching year at 4 colonies near
Hastings NHR, 9 (2.6%, all males) were later observed to breed (Reynolds 1995).
Mean natal dispersal distance of the young that recruited into their natal colony
was 247.4 m (SD = 173.2, n = 5) and the mean natal dispersal distance of those
that were found in another colony was 1,259.8 m (SD = 283.3, n = 4). Many young
likely disperse greater distances and females probably disperse farther than
males.
MANAGEMENT ISSUES:
Habitat loss and alteration: Yellow-billed Magpies are dependent on the preservation of oak savanna habitat for their continued existence. This habitat has been greatly reduced and is under current threat from housing development and intensified agriculture.
Poisoning: Yellow-billed Magpies appear to be especially sensitive to harm from broadcast poisoning of ground squirrels with compound 1080.
ASSOCIATED SPECIES:
No direct data, but presumably other oak savanna birds (and other animals) would
benefit from preservation or restoration of habitat for Yellow-billed Magpies.
Other oak savanna nesting species: Acorn Woodpecker, Oak Titmouse, Blue-gray
Gnatcatcher, Hutton's Vireo, Oak Titmouse.
MONITORING METHODS AND RESEARCH NEEDS:
Monitoring focused on breeding colonies is needed to learn more about the effects
of habitat alteration and fragmentation on Magpie populations. A minimal-effort
program could involved simple annual censuses of breeding colonies (to learn
if colonies are persisting or being lost/created) and a hierarchical program
could also include more intensive monitoring of the reproductive success of
a subset of colonies. Such monitoring programs should focus on populations located
near possible threats (human development or poisoning programs). Research also
is needed to better understand the habitat requirements for breeding colonies
and the effects of habitat alteration on population persistence.
Action plan summary
STATUS: No official conservation status. BBS results suggest a fairly stable population in California as a whole, but there has been some reduction in range (the loss of populations from the South Coast and southern San Joaquin Valley is based on historical data). Entire breeding range of this species is within California.
HABITAT NEEDS: Dependent on oak savanna habitat, where large trees are found within large expanses of open ground, especially valley floors, gentle slopes and open park-like areas, including along stream courses. Grasslands, pasture, or cultivated fields needed for foraging.
CONCERNS: Of primary concern are the effects of loss and alteration of oak savanna habitat. This habitat has been greatly reduced and is under current threat from housing development and intensified agriculture. The effects of this on Yellow-billed Mapgie populations appear to be negative but are not well understood. An additional concern is the effect of poisoning; Yellow-billed Magpies appear to be especially sensitive to harm from broadcast poisoning of ground squirrels with compound 1080.
OBJECTIVES: Protect existing habitat, identify healthy breeding populations, encourage monitoring and research designed to increase understanding of habitat requirements, habitat selection, factors affecting colony formation and persistence.
RECOMMENDED ACTIONS:
Establish monitoring program focused on breeding colonies to learn more about
the effects of habitat alteration and fragmentation on Magpie populations. Such
monitoring programs should focus on populations located near possible threats
(human development or poisoning programs). A minimal-effort program could involved
simple annual censuses of breeding colonies (to learn if colonies are persisting
or being lost/created). A more intensive program could also include monitoring
of the reproductive success and adult survival at a subset of colonies.
Conduct research to better understand the habitat requirements for breeding colonies and the effects of habitat alteration on population persistence.
Communicate habitat needs of Yellow-billed Magpies to land managers, planners, and regulatory agencies.
SCIENTIFIC REFERENCES:
Birkhead, T. R., K. Clarkson, M. D. Reynolds, and W. D. Koenig. 1992. Copulation and mate guarding in the colonial Yellow-billed Magpie and a comparison with the solitary Black-billed Magpie. Behaviour 121:110-130.
Bond, R. M. 1941. Yellow-billed Magpies on a coastal slope of Santa Barbara County, California. The Condor 43:247.
Grinnell, J., and A. H. Miller. 1944. The distribution of the birds of California. Pacific Coast Avifauna 27.
Harrison, H. H. 1979. A field guide to western birds nests. Houghton Mifflin, Boston.
Koenig, W. D., and M. D. Reynolds. 1987. Potential poisoning of Yellow-billed Magpies by compound 1080. Wildlife Society Bulletin 15:274-276.
Linsdale, J. M. 1937. The natural history of magpies. Pacific Coast Avifauna 25.
Linsdale, J. M. 1946. Yellow-billed Magpie. Pages 155-183 in A. C. Bent, editor. Life histories of North American jays, crows, and titmice. U.S. National Museum Bulletin 191.
Reynolds, M. D. 1990. The ecology of spacing behavior in the Yellow-billed Magpie Pica nuttalli. Ph.D. dissertation. University of California, Berkeley.
Reynolds, M. D. 1995. Yellow-billed Magpie (Pica nuttalli). In A. Poole and F. Gill, editors. The Birds of North America, No. 180. The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.
Sauer, J. R., J. E. Hines, and J. Fallon. 2002. The North American Breeding Bird Survey, Results and Analysis 1966 - 2001. Version 2002.1, USGS Patuxent Wildlife Research Center, Laurel, MD http://www.mbr-pwrc.usgs.gov/bbs/bbs2001.html
Verbeek, N. A. M. 1973. The exploitation system of the Yellow-billed Magpie. University of California Publications in Zoology 99:1-58.
Personal Communications
Kreitinger, Kimberly. 2002. California State University Stanislaus, Endangered
Species Recovery Program.