San Francisco State University
Geography 316: Biogeography
11/20/00 updated
The Biogeography of the Yellow-billed Magpie (Pica nuttalli)
by Jennifer Mar, student in Geography 316, Fall 1999
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Corvidae
Genus: Pica
Species: Pica nuttalli
Description of Species
The yellow-billed magpie (Pica nuttalli) is a
medium-sized bird that is sixteen to eighteen inches long from the tip of the bill to the
tip of the tail, and the tail is nine to ten inches long. It weighs 150 to 170
grams. It has a yellow bill and a yellow patch of bare skin, which is variable in
size around its eyes. The head and upper parts of the body are black with white
scapulars (a group of feathers on the shoulders), primaries (the outermost and longest
flight feathers on the wing), and a white lower breast and upper belly. There is a
blue, violet, and green iridescence on the wings and on the long, graduated tail.
Males and females are alike in plumage, but males are larger than females. Immature
yellow-billed magpies are less iridescent than adults, and have a slight brownish coloring
on the head, back, and wing coverts. Immature birds also have rounded rather than
square-tipped rectrices (long flight feathers on the tail) and a broader black tip on the
outermost primary feather (Reynolds 1995).
The black-billed magpie (Pica pica) looks almost the same as the
yellow-billed magpie except that it has a black beak, no bare spots around its eyes, and
less iridescence. It is also slightly larger at 17.5 to 23.5 inches in length and
weighing 145 to 210 grams.
Distribution
Yellow-billed magpies are only found in California and so are endemic
to California. One of the few birds that nests only in California, the yellow-billed
magpie is the only species never recorded outside its native state (Beedy & Granholm
1985). They are found west of the Sierra Nevada from Shasta County at the north end
of the Sacramento Valley, southward to Santa Barbara and Kern Counties, but they are
mainly in the Sacramento and San Joaquin Valleys and the coastal valley south of San
Francisco County. The amount of area they occupy is less than 150 miles wide and
extends 500 miles from north to south (Bent 1946). They are sedentary, so they
usually stay in this range and do not migrate. Although they do wander locally in
the non-breeding season, yellow-billed magpies usually stay within the breeding areas
(Reynolds 1995).
Most parts of the Sacramento and San
Joaquin valleys have an interior Mediterranean climate with hot summers and mild
winters. There are less winter storms and precipitation as one travels
southward. Some areas have frequent high winds. From the end of November
through January, fog forms after heavy rains and high humidity. Grasslands and oak
woodlands are common here. The inland Central Coast has a similar climate and
scattered oaks in grasslands (Peter 1997).
Habitat
Yellow-billed magpies prefer tall oak groves or stands of tall trees
along a stream or in park-like groves on valley floors or hills. They are also found
in open, partly wooded areas like savannas, grasslands, well-kept orchards, and cultivated
or farming lands. They stay near water for nest-building, drinking, and dunking
their food. Yellow-billed magpies, however, stay out of the areas that have frequent
high winds, long, snowy, and cold winters, or especially dry and hot summers because these
factors limit their food supply (Linsdale 1937).
The North American black-billed magpie (Pica pica hudsonia) is
similar to the yellow-billed magpie, but one of their differences is where they
live. P. p. hudsonia is common in the western half of North America, but in
California, it is only found along the eastern base of the Sierra Nevada and very rarely
appears on the west slope (Beedy & Granholm 1985). The boundaries of the two
birds do not overlap as the gap separating them is 50 miles wide at its narrowest place
(Bent 1946). Even if the two species were to meet, they have been isolated from each
other so long that they are probably distinct enough to be unable to breed (Birkhead
1991).
Natural History
FOOD
Since yellow-billed magpies are
quite large, they mostly feed on the ground preferring grazed rather than ungrazed
pastures (Reynolds 1995). They also forage in areas near water and areas with high
groundwater levels like meadow after heavy rains because worms and insects are abundant
(Reynolds 1995). During the breeding season, they look for food in small flocks, and
during the non-breeding season, they search in large flocks (Reynolds 1995). Less
often, yellow-billed magpies search for food in oak understories and mid canopies of trees
(Reynolds 1995). In the summer, they eat insects and other animals, and in the
winter, they eat more plant products. If there are any carcasses around during
anytime of the year, they will make use of those. They can also catch small
vertebrates on their own. Food is most abundant in April and May, and is least
abundant in August and September. Since there is a lot of food in the summer, the
magpies can afford to be selective (Birkhead 1991). The interior of California
becomes very hot in the summer, so the birds look for food in the early hours of the
morning when it is cooler. When winter sets in, the birds feed mostly in the
afternoon.
Both the yellow-billed and the black-billed magpies (Pica pica)
are short-term hoarders; they cache and recover food either on the same day or a few days
later. The caches are usually less than fifty meters from where they found the food
(Reynolds 1995). Most of the food caches are dug shallowly in the ground and covered
with leaves, grass, or lichen. The food in the caches include acorns, fruit, dog
food, and small mammals. Although, yellow-billed magpies hoard food throughout the
year, acorn hoarding is done from October to December. The acorns are sometimes
partially eaten before they are buried. American crows often raid the caches that
contain dog food and acorns (Reynolds 1995). The birds often recover hidden food by
flying straight to the cache and digging or probing into a crevice for the food in
"an assured and confident manner" (Goodwin 1976). Food not eaten often
germinate and result in the growth of more trees, which help in the maintenance of
watersheds, soil development, and provide future food sources (Angell 1978).
BREEDING
Both species, the black-billed and the yellow-billed magpies are
monogamous. The bond may last for many years, and the yellow-billed magpies may stay
paired for life until one bird dies (Reynolds 1995). Breeding birds remain near
their territories throughout the year and often reuse nests in the same territory in
successive year (Birkhead 1991). Adult birds that lost a mate stayed with the flock,
which may have helped it find a new mate (Birkhead 1991).
Male magpies sing during the early part of the breeding
season. The three types of songs recognized are soft singing, rhythmic singing, and
babble singing (Birkhead 1991). all three songs are quiet. The babble song is
a series of soft, warbling notes with many higher pitched sounds and whistles. Some
yellow-billed magpies use the sounds of other birds or animals into the song. Males
often sing two weeks before the females lay eggs and one possible function of the songs is
to stimulate her to lay eggs (Birkhead 1991). During the last five days before the
female lays the first egg, most of the courtship behaviors take place.
P. nuttalli uses the same social signals as P. pica but
also uses bill-nibbling and tugging (Birkhead 1991). The bill-nibbling may be part
of the ritual of one bird preening another, accompanied by a soft warbling call.
Tugging is when a male picks up a small leaf stalk or twig and presents it to the
female. While making soft vocalizations, the two birds tug at it until the female
gets it, and then she drops it. These behaviors are preliminary courtship behaviors.
Courtship can be performed on the ground or in the trees. The
first display, uncommonly performed, involves the male circling his partner about half a
meter away. Circling begins two weeks before eggs are laid and most often occurs
four to five days before the first egg is laid. The male's white feathers are
fluffed until he looks spherical, and he stands in an upright posture, tilting his tail
towards the female (Birkhead 1991). As he approaches the female, he sings the babble
song and uses wing-flirting and wing-quivering to attract her. At the end, the
female walks or hops away, and the male follow.
Next, the female initiates copulation with two calls. the first
one is a harsh call produced several minutes before copulation. The second
vocalization is a low amplitude, repetitive growling call, which occurs just before she
crouches with drooping, outspread wings, and lifts her tail (Reynolds 1995).
Approaching quickly, the male mounts for two seconds. Copulation occurs mostly in
the morning on the fifth, fourth, or third days before the first egg is laid.
Yellow-billed magpies copulate three or four times for each clutch (Birkhead 1991).
A unique courtship ritual that female magpies perform is begging.
Several days, usually two days, before the female lays her first egg, she begs noisily and
crouches in front of him, flapping her wings and making a high pitched whining call.
He ignores her at first and then feeds her when she has started to lay eggs or has begun
incubating. The yellow-billed and black-billed magpies start food begging two days
before the first egg is laid, but European magpies begin just one day before the first egg
is laid (Birkhead 1991).
NESTS
Yellow-billed magpies generally nest in loose colonies of three
to thirty pairs, although some nest solitarily (Reynolds 1995). they build bulky
nests out of sticks on the tops of tall trees in loose colonies. The nests in oaks,
cottonwoods, or sycamores are often used by American kestrels, long-eared owls and other
birds after the magpies finish using them (Beedy & Granholm 1985).
Nest building begins in late December at the earliest, and by the
middle of February, practically all breeding pairs are in the process of nest
building. It takes six to eight weeks to finish a nest, but nests from previous
seasons are sometimes reused and repaired in less than two weeks (Reynolds 1995).
Most of the construction takes place in the mornings on sunny days. Both male and
female help build it, although the female does most of the work on finishing the nest
bowl.
The nests are built high up in large trees, which are often oak
trees. The average height above the ground is 16.9 meters (52 feet), and this may
discourage predators (Birkhead 1991). They are also at the end of a branch with no
side limbs, possibly to avoid tree climbing snakes such as the gopher snake, who eats eggs
and nestlings (Birkhead 1991). Yellow-billed magpies nest in valley oak, blue oak,
coast live oak, western sycamore, black cottonwood, and Fremont cottonwood trees most
often. The introduced trees that are also used are black locust, blue gum, and fruit
trees such as walnut trees. Occasionally, Monterey pine, gray pine, Monterey
cypress, and willows are used. Valley oaks and coast live oaks make up 71.3% of the
yellow-billed magpies' nesting trees. Valley oak trees are used most often as
nesting trees at 35.7%, coast live oaks at 35.7%, and blue oaks make up 13.9% (Reynolds
1995). |
They nest in trees with many clumps of mistletoes on it, or sometimes
build within the clump. In California, two kinds of mistletoes that look similar to
the yellow-billed magpie's nest occur within its range (Linsdale 1937). Trees that
have these kinds of mistletoes are valley oaks, cottonwoods, and sycamore. The nest
resembles a clump of mistletoe since they are similar in size, shape, and position (Bent
1946). Other organisms may mistake the nest for mistletoe and leave the nest alone
(Linsdale 1937).
The nest is globe-shaped and about 0.9 meters in diameter.
Verbeek (1973) dismantled a nest and counted 1,573 sticks, most of which is in the dome
instead of the bowl (Birkhead 1991). They weighed 11 kilograms or 24.4 pounds,
almost 70 times the weight of a yellow-billed magpie (Birkhead 1991). Roofed nests
of magpies breeding in hot areas may control the amount of solar heat reaching the
incubating adult and its young (Angell 1978).
Evolution
The common name of "magpie" is from the contraction of
Magot Pie, a middle English name for the birds. "Magot" comes from the
name Margot, which signifies a magpie whose chattering was believed to sound like a
chattering woman (Birkhead 1991). "Pie" comes from pica, which
means the black and white coloring of the bird. The name was first recorded in 1605
and became standard after Thomas Pennant published his book British Zoology (Birds)
in 1768 (Birkhead 1991).
In 1937, John James Audubon named the yellow-billed magpie Corvus
nutalli, which was later changed to nuttalli in honor of Thomas Nuttall, an
ornithologist who collected specimens near Santa Barbara (Reynolds 1995). Nuttall,
born in 1786 and died in 1859, was an English botanist and ornithologist who lived in the
United States. The name was changed to Pica because Corvus refers to
crows and ravens. The Latin word pica means magpie, and is used for birds
that are pied, which means having patches of two or more colors. In this case, the
colors are black and white.
The order Passeriformes is the dominant order of modern birds, which
has more than half of the living bird species. It is relatively recent and highly
successful. Birds in this order are perching birds, meaning that their feet are
designed to automatically wrap around branches. Included in this order are the
songbirds like robins, finches, sparrow, and jays. The earliest known passerine
fossils appeared late in the Eocene epoch (40 mya) and is considered that most highly
evolved of all birds (Encyclopaedia Britannica 1998). It had high evolutionary
radiation and has adapted to all continents except Antarctica and most oceanic
islands. These factors have led to a large number of species in the order with 5100
species compared to 3500 species of all other birds (Encyclopaedia Britannica 1998).
Because passerines are rarely fossilized, their origins are educated guesses. Some
believe that they evolved in the Cretaceous era 120 mya, and some say that they evolved
later in the Cretaceous or in the Paleocene epoch 65 mya (Encyclopaedia Britannica 1998).
Birds are rarely fossilized because they have delicate structures and
are often eaten. Because of this lack of a fossil record, there is no information
about the types of birds from which passerines arose. However, studies show that
passerines have a polyphyletic origin, meaning that they have evolved from more than one
ancestor (Encyclopaedia Britannica 1998).
Containing 102 species, the Corvidae family has the largest amount of
adaptive radiation and differentiation than any of the other passerine families (Goodwin
1976). This family includes crows, ravens, jays, and magpies. Dry conditions
in the Miocene epoch, which lasted between 26 to 7 mya, initiated the spread of grasslands
and the reduction of forests (Encyclopaedia Britannica 1998). Families of birds
adapted to this drier and less forested habitat. The earliest remains of crows were
found from this epoch (Encyclopaedia Britannica 1998). Warm, dry conditions
continued through the Pliocene epoch (7-2.5 mya), and by this time, all living passerine
families were in existence by its end (Encyclopaedia Britannica 1998).
The members of the genus Pica probably traveled to North America
across the Bering Land Bridge between North America and Eurasia sometime during the
Cenozoic era beginning 65 mya before humans did (Trost 1999). some of the
Pleistocene records show that black-billed magpies used to inhabit northwest Alabama,
Virginia, the Texas panhandle, and Shelter Caves, New Mexico -- areas outside their
present ranges. They are now found in the western part of North America and Alaska.
Pica nuttalli has no subspecies, but the closely related
black-billed magpie (Pica pica) has thirteen subspecies. The only subspecies
found in North America is Pica pica hudsonia. The yellow-billed magpie and
the North American subspecies of 
black-billed magpie are more similar to each other in terms of vocalization
and social behavior than they are to the Eurasian subspecies of black-billed magpies
(Reynolds 1995). The yellow-billed magpie has a smaller body size than most of the
subspecies of the black-billed magpie but has longer wings for its body size. This
may be because of its colonial breeding and greater amounts of flying from its colony to
the feeding areas (Reynolds 1995).
Fossils from the late Pleistocene epoch, which began 1.8 mya, were
found at Rancho La Brea, Los Angeles County; Carpenteria, Santa Barbara County; and
McKittrick, Kern County (Reynolds 1995). Carpenteria and Rancho La Brea are areas
south of the southernmost boundary of the yellow-billed magpie's present range.
Yellow-billed magpies were the most abundant passerines in some of the Rancho La Brea
deposits. The age of the fossils suggests that the yellow-billed magpie may be a
relict from the last glaciation and that the North American black-billed magpies may be a
more recent species from Asia (Reynolds 1995).
Although P. nuttalli's evolutionary history has not been
extensively studied, there are several theories about its past. One theory says that
P. nuttalli and P. pica may have been separated during the Sierra Nevada
elevation in the Pliocene epoch between 5.3 and 1.8 mya (Trost 1999). Another theory
suggests that yellow-billed magpies went extinct except for a population in California,
while the black-billed magpies are a recent migrant from Asia (Trost 1999). However,
some observation s are starting to dismiss the latter theory (Trost 1999).
Other interesting facts
Black plumage is more efficient at absorbing solar energy than other
colors, so the black color maintains body heat more efficiently at low temperatures if
sunlight is available (Goodwin 1976). Black feathers absorb short wavelength solar
energy and decrease the temperature gradient between the skin and outer feathers (Angell
1978). A black colored birds can extend its range into colder environments if
blackness does help in maintenance of boy temperature and conservation of body
energy. On cold mornings, black helps in quick warming through solar energy
absorption. For example, magpies and other black feathered members of the Corvidae
family, eat early in the morning and in the evening, and are inactive at peak heat
hours. Also, feathers with dark melanin pigment are less susceptible to wear and
tear than unpigmented or less heavily pigmented ones (Angell 1978). The
yellow-billed magpie and the North American black-billed magpie are both heat intolerant,
but the yellow-billed magpies can deal with heat a little better (Reynolds 1995).
Magpies have short, rounded, broad, elliptical wings. Although
not good for fast, prolonged flights, they are designed for maneuvering in and out of
thick brush and dense woodland vegetation (Feduccia 1996). This type of wing is
characterized by a uniform pressure distribution over the wing surface and a convex
curvature. The long tail aids the rounded wings of the yellow-billed magpie fly up
or dodge quickly (Goodwin 1976). This is evident from their agility and quick
reactions when they bob predators. However, the tail appears to be an inconvenience
when flying some distance in the open (Goodwin 1976). the earliest known bird, Archaeopteryx,
had this type of elliptical wing (Feduccia 1996).
Is this the face of a thief?
Magpies are known as thieves because shiny valuables are sometimes
found in their nests as in Gioacchino Rossini's opera La Gazza Ladra or The
Thieving Magpie. However, magpies do not normally store food there.
Goodwin thinks that this behavior may be an extension of or a substitution for their
normal food-hiding behavior. Young corvids investigate objects and "test"
their possibility as food, so during this period, the food-hiding behavior may be indulged
with inedible objects. The birds normally look for edibles and don't hid e inedible
objects. Tame or captive magpies are given food, so that there isn't a normal outlet
for food-seeking. As a result, they investigate everything, and they especially like
objects that make loud noise when dragged or thrown off a ledge. Goodwin has not
observed any special attraction for shiny objects among magpies. They may take
valuables because their owners do not allow then to handle them. The magpies assume
that it may be valuable like food and are determined to get a hold of the objects.
Bibliography
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Seattle, Washington. University of Washington Press.
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14. Reynolds, Mark D. 1995. "Yellow-billed Magpie (Pica nuttalli)." The Birds of America, No. 180 (A. Poole and F. Gill, eds.). Philadelphia, Pennsylvania. The Academy of Natural Sciences and The American Ornithologists' Union.
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The birds of North America, No. 389 (A. Poole and F. Gill, eds.). The Birds of North
America, Inc. Philadelphia, Pennsylvania.
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