Black-billed magpie, Pica hudsonia (P. pica: LC)

The black-billed magpie (Pica hudsonia), also known as the American magpie, is a bird in the crow family that inhabits the western half of North America, from southern coastal Alaska to northern California, northern Nevada, northern Arizona, northern New Mexico, central Kansas, and Nebraska. It is black and white, with black areas on the wings and tail showing iridescent hints of blue or blue-green. It is one of only four North American songbirds whose tail makes up half or more of the total body length (the others being the yellow-billed magpie, the scissor-tailed flycatcher, and the fork-tailed flycatcher) [1].

Black-Billed Magpie

Black-billed magpie, Pica hudsonia

Black-billed magpies range in the north from coastal southern Alaska, central British Columbia, and the southern halves of Alberta, Saskatchewan, and Manitoba, through the Rocky Mountains down south to all the Rocky Mountain states including New Mexico, Colorado, Utah, Wyoming, Idaho, and some bordering states as well. The range extends as far east as northern Minnesota and Iowa, with casual records in northern Wisconsin and upper Michigan, but is thought to be limited further east and south by high temperature and humidity. [1]

Black-billed magpies frequent open country with thickets and scattered trees, especially riparian groves. They can be found near farms and within cities and suburbs. Dry open pine forests are another possible habitat. [1]

This species prefers generally open habitats with clumps of trees. It can therefore be found in farmlands and suburban areas, where it comes into regular contact with people. Where persecuted it becomes very wary, but otherwise it is fairly tolerant of human presence. Historically associated with bison herds, it now lands on the back of cattle to glean ticks and insects from them. Large predators such as wolves are commonly followed by black-billed magpies, who scavenge from their kills. The species also walks on the ground, where it obtains such food items as beetles, grasshoppers, worms, and small rodents. [1]

The black-billed magpie is an opportunistic omnivore, eating many types of insects, carrion, seeds, rodents, berries, nuts, eggs, and also garbage and food from pets that are fed outside. Chicks are fed animal matter almost exclusively. Magpies typically forage on the ground, usually walking, sometimes hopping, and sometimes scratching with their feet to turn over ground litter. They sometimes land on large mammals, such as moose or cattle, to pick at the ticks that often plague these animals. They often follow large predators, such as wolves, to scavenge or steal from their kills. [1]

Black-billed magpies are also known to make food caches in the ground, in scatter-hoarding fashion. To make a cache, the bird pushes or hammers its bill into the ground (or snow), forming a small hole into which it deposits the food items it was holding in a small pouch under its tongue. It may, however, then move the food to another location, particularly if other magpies are in the vicinity, watching. Cache robbing is fairly common so a magpie often makes several false caches before a real one. The final cache is covered with grass, leaves, or twigs. After this the bird cocks its head and stares at the cache, possibly to commit the site to memory. Such hoards are short-term; the food is usually recovered within several days, or the bird never returns. The bird relocates its caches by sight and also by smell; during cache robbing, smell is probably the primary cue.[1]

The black-billed magpie is one of the few North American birds that build a domed nest. This nest is made up of twigs and sits near the top of trees. Usually 6-7 eggs are laid. Incubation, by the female only, starts when the clutch is complete, and lasts 16–21 days. The nestling period is 3–4 weeks. [1]

The adult black-billed magpie is 45–60 cm (18–24 in) long and weighs 145–210 g (5.1–7.4 oz). Males are generally 6–9% larger and 16–20% heavier than females. The tail is long and makes up half of the bird's length. Wingspan is about 60 cm (24 in). The bird is black with white shoulders, a white belly, and iridescent dark blue-green wings and tail. There are large white markings on the primaries, clearly visible in flight. The feet and bill are black. [1]

The breeding season for magpies is generally from late March to early July. They nest once a year, but may re-nest if their first attempt fails early. The female lays up to thirteen eggs, but the usual clutch size is six or seven. The eggs are greenish grey, marked with browns, and 33 mm (about 1.3 inch) long. Only the female incubates, for 16–21 days. The male feeds the female throughout incubation. Hatching is often asynchronous. Hatched young are altricial, brooded by the female but fed by both sexes. They fly 3–4 weeks after hatching, feed with adults for about two months, and then fly off to join other juvenile magpies. Fledging success (usually 3–4 young per nest) is lower than clutch size; this is not an unusual state of affairs in species with asynchronous hatching, as some nestlings often die of starvation. [1]

Adult black-billed magpie pairs stay together year-round and often for life unless one dies, in which case the remaining magpie may find another mate. Divorces are possible: one South Dakota study found low rates of divorce (8%)[9] but one 7-year study in Alberta found divorce rates up to 63%. [1]

Black-billed magpies nest individually, frequently toward the top of deciduous or evergreen trees. Only the nest tree and its immediate surroundings are defended, and so it is possible for nests to be somewhat clumped in space. When this happens (usually in areas with a limited number of trees or with abundant food resources), a diffuse colony is formed. In this the black-billed magpie is intermediate between the European magpie, whose nests are much more spread out because a large territory is defended around each nest, and the yellow-billed magpie, which is always loosely colonial. [1]

Nests are loose but large accumulations of branches, twigs, mud, grass, rootlets, bark strips, vines, needles, and other materials, with branches and twigs constituting the base and framework. The nest cup is lined with fine rootlets, grass, and other soft material. Nests almost always include a hood or dome of loosely assembled twigs and branches, and usually have one or more side entrances. Nests are built by both sexes over 40–50 days, starting in February (though later in northern parts of the range). Old nests can be repaired and used, or a new nest can be built on top, with older nests thus reaching 120 cm high by 100 cm wide (48 inches high by 40 inches wide). Other bird species, including small hawks and owls, often use old magpie nests. [1]

Black-billed magpies breed for the first time at 1 or 2 years of age. The lifespan of the species in the wild is about four to six years. [1]

American crow, Corvus brachyrhynchos LC

The American crow (Corvus brachyrhynchos) is a large passerine bird species of the family Corvidae. It is a common bird found throughout much of North America. American crows are the new world counterpart to the carrion crow and the hooded crow. Although the American crow and the hooded crow are very similar in size, structure and behavior, their calls are different. The American crow nevertheless occupies the same role the hooded crow does in Eurasia. [2]

American Crow

American crow, Corvus brachyrhynchos

The range of the American crow now extends from the Pacific Ocean to the Atlantic Ocean in Canada, on the French islands of Saint-Pierre and Miquelon, south through the United States, and into northern Mexico. The increase in trees throughout the Great Plains during the past century due to fire suppression and tree planting facilitated range expansions of the American crow as well as range expansions of many other species of birds. Virtually all types of country from wilderness, farmland, parks, open woodland to towns and major cities are inhabited; it is absent only from Pacific temperate rain forests and tundra habitat where it is replaced by the raven. This crow is a permanent resident in most of the USA, but most Canadian birds migrate some distances southward in winter. Outside of the nesting season these birds often gather in large (thousands or even millions) communal roosts at night. [2]

From beak to tail, an American crows measures 40–50 cm (16–20 in), almost half of which is tail. Mass varies from about 300 to 600 g (10 to 20 oz). Males tend to be larger than females. The most usual call is CaaW!-CaaW!-CaaW!. [2]

The American crow is all black, with iridescent feathers. It looks much like other all-black corvids. They can be distinguished from the common raven (C. corax) because American crows are smaller and from the fish crow (C. ossifragus) because American crows do not hunch and fluff their throat feathers when they call. [2]

American crows are common, widespread, and susceptible to the West Nile virus, making them useful as a bioindicator to track the virus's spread. Direct transmission of the virus from American crows to humans is unheard of and unlikely. [2]

The American crow is a distinctive bird with iridescent black feathers all over. Its legs, feet and bill are also black. They measure 40–53 cm (16–21 in) in length, of which the tail makes up about 40%. The wing chord is 24.5 to 33 cm (9.6 to 13.0 in), with the wingspan ranging from 85 to 100 cm (33 to 39 in). The bill length can be from 3 to 5.5 cm (1.2 to 2.2 in), varying strongly according to location. The tarsus is 5.5 to 6.5 cm (2.2 to 2.6 in) and the tail is 13.5 to 19 cm (5.3 to 7.5 in). The body mass can vary from 316 to 620 g (11.1 to 21.9 oz). Males tend to be larger than females. [2]

The most usual call is a loud, short, and rapid caaw-caaw-caaw. Usually, the birds thrust their heads up and down as they utter this call. American crows can also produce a wide variety of sounds and sometimes mimic noises made by other animals, including other birds. [2]

Visual differentiation from the fish crow (C. ossifragus) is extremely difficult and often inaccurate. Nonetheless, differences apart from size do exist. Fish crows tend to have more slender bills and feet. There may also be a small sharp hook at the end of the upper bill. Fish crows also appear as if they have shorter legs when walking. More dramatically, when calling, fish crows tend to hunch and fluff their throat feathers. [2]

If seen flying at a distance from where size estimates are unreliable, the distinctly larger common ravens (C. corax) can be distinguished by their almostl ozenge-shaped tail and their larger-looking heads. They also fluff their throat feathers when calling like fish crows, only more so.[2]

The American crow is omnivorous. It will feed on invertebrates of all types, carrion, scraps of human food, seeds, eggs and nestlings, stranded fish on the shore and various grains. American crows are active hunters and will prey on mice, frogs, and other small animals. In winter and autumn, the diet of American crows is more dependent on nuts and acorns. Occasionally, they will visit bird feeders. The American crow is one of only a few species of bird that has been observed modifying and using tools to obtain food. [2]

Like most crows, they will scavenge at landfills, scattering garbage in the process. Where available, corn, wheat and other crops are a favorite food. These habits have historically caused the American crow to be considered a nuisance. However, it is suspected that the harm to crops is offset by the service the American crow provides by eating insect pests.[2]

American crows are socially monogamous cooperative breeding birds. Mated pairs form large families of up to 15 individuals from several breeding seasons that remain together for many years. Offspring from a previous nesting season will usually remain with the family to assist in rearing new nestlings. American crows do not reach breeding age for at least two years. Most do not leave the nest to breed for four to five years. [2]

The nesting season starts early, with some birds incubating eggs by early April. American crows build bulky stick nests, nearly always in trees but sometimes also in large bushes and, very rarely, on the ground. They will nest in a wide variety of trees, including large conifers, although oaks are most often used. Three to six eggs are laid and incubated for 18 days. The young are usually fledged by about 36 days after hatching. Predation primarily occurs at the nest site and eggs and nestlings are frequently eaten by snakes, raccoons, ravens and domestic cats. Adults are less frequently predated but face potential attack from great horned owls, red-tailed hawks, peregrine falcons and eagles. They may be attacked by predators such as coyotes or bobcats at carrion when incautious although this is even rarer. [2]

The average life span of the American crow in the wild is 7–8 years. Captive birds are known to have lived up to 30 years. [2]

 

Northwestern crow, Corvus caurinus LC

The northwestern crow (Corvus caurinus) is an all-black passerine bird of the crow genus native to the northwest of North America. It is very similar to the more western forms of the widespread American crow (Corvus brachyrhynchos), but it averages slightly smaller (33–41 cm in length) with proportionately smaller feet and a slightly more slender bill. This taxon is reliably identified by range only. [3]

Northwestern Crow

Northwestern crow, Corvus caurinus

This species' plumage is virtually identical to that of the American crow. Individuals may be distinguished by in-hand criteria such as smaller wing chord and tail length, shorter tarsus, and smaller bill. Identification percentages increase when sex of animal is known. Like the American crow, the sexes look the same. Older birds in breeding condition may be reliably sexed by in-hand criteria such as cloacal protuberance (male) or by brood patch (female). Younger birds may not attain breeding condition as they assist at the nest. [3]

This species occurs in coastal regions and offshore islands of southern Alaska, south through British Columbia to Washington state. Beaches and shorelines are the principal forage areas. It can often be seen in and around urban areas. [3]

Very similar to that of the fish crow; the northwestern crow eats stranded fish, shellfish, crabs and mussels, and also searches through refuse containers for suitable food items. It has been seen to fly into the air with mussels and drop them onto hard surfaces to break them open. It also regularly eats insects, other invertebrates, and various fruits (especially berries). It raids other birds' nests to eat eggs and hatchlings. [3]

This bird is generally solitary, but sometimes builds its nest in association with a few other individuals in small, loose colonies in trees or sometimes large bushes. Very rarely, it will nest on cliffs in a recess or even on the ground in a remote area if overhung by a rock for shelter. It is a typical crow nest with 4-5 eggs usually laid. [3]

 

Common raven, Corvus corax LC

The common raven (Corvus corax), also known as the northern raven, is a large all-black passerine bird. Found across the Northern Hemisphere, it is the most widely distributed of all corvids. There are at least eight subspecies with little variation in appearance, although recent research has demonstrated significant genetic differences among populations from various regions. It is one of the two largest corvids, alongside the thick-billed raven, and is possibly the heaviest passerine bird; at maturity, the common raven averages 63 centimetres (25 inches) in length and 1.2 kilograms (2.6 pounds) in mass. Common ravens can live up to 21 years in the wild, a lifespan exceeded among passerines by only a few Australasian species such as the satin bowerbird and probably the lyrebirds. Young birds may travel in flocks but later mate for life, with each mated pair defending a territory. [4]

Raven

Common raven, Corvus corax

Common ravens have coexisted with humans for thousands of years and in some areas have been so numerous that people have regarded them as pests. Part of their success as a species is due to their omnivorous diet; they are extremely versatile and opportunistic in finding sources of nutrition, feeding on carrion, insects, cereal grains, berries, fruit, small animals, and food waste. [4]

Some notable feats of problem-solving provide evidence that the common raven is unusually intelligent. Over the centuries, it has been the subject of mythology, folklore, art, and literature. In many cultures, including the indigenous cultures of Scandinavia, ancient Ireland and Wales, Bhutan, the northwest coast of North America, and Siberia and northeast Asia, the common raven has been revered as a spiritual figure or god. [4]

A mature common raven ranges between 54 and 67 cm (21" and 26") long, with a wingspan of 115 to 130 cm (45-51").[ Recorded weights range from 0.69 to 2 kg (1.5 to 4.4 lb), thus making the common raven one of the heaviest passerines. Birds from colder regions such as the Himalayas and Greenland are generally larger with slightly larger bills, while those from warmer regions are smaller with proportionally smaller bills. Representative of the size variation in the species, ravens from California weighed an average of 784 g (1.728 lb), those from Alaska weighed an average of 1,135 g (2.502 lb) and those from Nova Scotia weighed an average of 1,230 g (2.71 lb). The bill is large and slightly curved, with a culmen length of 5.7 to 8.5 cm (2.2 to 3.3 in), easily one of the largest bills amongst passerines (perhaps only the thick-billed raven has a noticeably larger bill). It has a longish, strongly graduated tail, at 20 to 26.3 cm (7.9 to 10.4 in), and mostly black iridescent plumage, and a dark brown iris. The throat feathers are elongated and pointed and the bases of the neck feathers are pale brownish-grey. The legs and feet are good-sized, with atarsus length of 6 to 7.2 cm (2.4 to 2.8 in). Juvenile plumage is similar but duller with a blue-grey iris. [4]

Apart from its greater size, the common raven differs from its cousins, the crows, by having a larger and heavier black beak, shaggy feathers around the throat and above the beak, and a wedge-shaped tail. Flying ravens are distinguished from crows by their tail shape, larger wing area, and more stable soaring style, which generally involves less wing flapping. Despite their bulk, ravens are easily as agile in flight as their smaller cousins. In flight the feathers produce a creaking sound that has been likened to the rustle of silk. The voice of ravens is also quite distinct, its usual call being a deep croak of a much more sonorous quality than a crow's call. In North America, the Chihuahuan raven (C. cryptoleucus) is fairly similar to the relatively small common ravens of the American southwest and is best distinguished by the still relatively smaller size of its bill, beard and body and relatively longer tail. All-black carrion crow (C. corone) in Europe may suggest a raven due to their largish bill but are still distinctly smaller and have the wing and tail shapes typical of crows. [4]

White ravens are occasionally found in the wild. Birds in British Columbia lack the pink eyes of an albino, and are instead leucistic, a condition where an animal lacks any of several different types of pigment, not simply melanin. [4]

Common ravens have a wide range of vocalizations which are of interest to ornithologists. Gwinner carried out important studies in the early 1960s, recording and photographing his findings in great detail. Fifteen to 30 categories of vocalization have been recorded for this species, most of which are used for social interaction. Calls recorded include alarm calls, chase calls, and flight calls. The species has a distinctive, deep, resonant prruk-prruk-prruk call, which to experienced listeners is unlike that of any other corvid. Its very wide and complex vocabulary includes a high, knocking toc-toc-toc, a dry, grating kraa, a low guttural rattle and some calls of an almost musical nature. [4]

Like other corvids, ravens can mimic sounds from their environment, including human speech. Non-vocal sounds produced by the common raven include wing whistles and bill snapping. Clapping or clicking has been observed more often in females than in males. If a member of a pair is lost, its mate reproduces the calls of its lost partner to encourage its return. [4]

Common ravens can thrive in varied climates; indeed this species has the largest range of any member of the genus, and one of the largest of any passerine. They range throughout the Holarctic from Arctic and temperate habitats in North America and Eurasia to the deserts of North Africa, and to islands in the Pacific Ocean. In the British Isles, they are more common in Scotland, Wales, northern England and the west of Ireland. In Tibet, they have been recorded at altitudes up to 5,000 m (16,400 ft), and as high as 6,350 m (20,600 ft) on Mount Everest. The population sometimes known as the Punjab raven—described as Corvus corax laurencei (also spelt lawrencii or laurencii) by Allan Octavian Hume but more often considered synonymous with subcorax—is restricted to the Sindh district of Pakistan and adjoining regions of northwestern India. Except in Arctic habitats, they are generally resident within their range for the whole year. Young birds may disperse locally. [4]

Most common ravens prefer wooded areas with large expanses of open land nearby, or coastal regions for their nesting sites and feeding grounds. In some areas of dense human population, such as California in the United States, they take advantage of a plentiful food supply and have seen a surge in their numbers.  On coasts, individuals of this species are often evenly distributed and prefer to build their nest sites along sea cliffs. Common ravens are often located in coastal regions because these areas provide easy access to water and a variety of food sources. Also, coastal regions have stable weather patterns without extreme cold or hot temperatures. [4]

In general, common ravens live in a wide array of environments but prefer heavily contoured landscapes. When the environment changes in vast degrees, these birds will respond with a stress response. The hormone known as corticosterone is activated by the hypothalamic–pituitary–adrenal axis. Corticosterone is activated when the bird is exposed to stress, such as migrating great distances. [4]

Common ravens are omnivorous and highly opportunistic: their diet may vary widely with location, season and serendipity. For example, those foraging on tundra on the Arctic North Slope of Alaska obtained about half their energy needs from predation, mainly of microtine rodents, and half by scavenging, mainly of caribou and ptarmigan carcasses. [4]

In some places they are mainly scavengers, feeding on carrion as well as the associated maggots and carrion beetles. With large-bodied carrion, which they are not equipped to tear through as well as birds such as hook-billed vultures, they must wait for the prey to be torn open by another predator or flayed by other means. Plant food includes cereal grains, berries and fruit. They prey on small invertebrates, amphibians, reptiles, small mammals and birds. Ravens may also consume the undigested portions of animal feces, and human food waste. They store surplus food items, especially those containing fat, and will learn to hide such food out of the sight of other common ravens. Ravens also raid the food caches of other species, such as the Arctic fox. They sometimes associate with another canine, the grey wolf, as a kleptoparasite, following to scavenge wolf-kills in winter. Ravens are regular predators at bird nests, brazenly picking off eggs, nestlings and sometimes adult birds when they spot an opportunity. They are considered perhaps the primary natural threat to the nesting success of the critically endangered California condor, since they readily take condor eggs and are very common in the areas where the species is being re-introduced.

Common ravens nesting near sources of human garbage included a higher percentage of food waste in their diet, birds nesting near roads consumed more road-killed vertebrates, and those nesting far from these sources of food ate more arthropods and plant material. Fledging success was higher for those using human garbage as a food source. In contrast, a 1984–1986 study of common raven diet in an agricultural region of south-western Idaho found that cereal grains were the principal constituent of pellets, though small mammals, grasshoppers, cattle carrion and birds were also eaten. [4]

One behavior is recruitment, where juvenile ravens call other ravens to a food bonanza, usually a carcass, with a series of loud yells. In Ravens in Winter, Bernd Heinrich posited that this behavior evolved to allow the juveniles to outnumber the resident adults, thus allowing them to feed on the carcass without being chased away. A more mundane explanation is that individuals co-operate in sharing information about carcasses of large mammals because they are too big for just a few birds to exploit. Experiments with baits however show that such recruitment behaviour is independent of the size of the bait. [4]

Furthermore, there has been research suggesting that the common raven is involved in seed dispersal. In the wild, the common raven chooses the best habitat and disperses seeds in locations best suited for its survival. [4]

Owing to its size, gregariousness and its defensive abilities, the common raven has few natural predators. Predators of its eggs include owls, martens, and sometimes eagles. Ravens are quite vigorous at defending their young and are usually successful at driving off perceived threats. They attack potential predators by flying at them and lunging with their large bills. Humans are occasionally attacked if they get close to a raven nest, though serious injuries are unlikely. There are a few records of predation by large birds of prey. Their attackers in America have reportedly included great horned owls, northern goshawks, bald eagles, golden eagles and red-tailed hawks, it is possible that the two hawks only have attacked young ravens, as had a peregrine falcon who in one instance swooped at a newly fledged raven but was successfully chased off by the parent ravens. In Eurasia, their reported predators include, in addition to golden eagles, Eurasian eagle-owls, white-tailed eagles, Steller's sea-eagles, eastern imperial eagles and gyrfalcons. Because they are potentially hazardous prey for raptorial birds, raptors must usually take them by surprise and most attacks are on fledgling ravens. More rarely still, large mammalian predators such as lynxes, coyotes and cougars have also attacked ravens. This principally occurs at a nest site and when other prey for the carnivores are scarce. Ravens are highly wary around novel carrion sites and, in North America, have been recorded waiting for the presence of American crows and blue jays before approaching to eat. [4]

Juveniles begin to court at a very early age, but may not bond for another two or three years. Aerial acrobatics, demonstrations of intelligence, and ability to provide food are key behaviors of courting. Once paired, they tend to nest together for life, usually in the same location.  Instances of non-monogamy have been observed in common ravens, by males visiting a female's nest when her mate is away. [4]

Breeding pairs must have a territory of their own before they begin nest-building and reproduction, and thus aggressively defend a territory and its food resources. Nesting territories vary in size according to the density of food resources in the area. The nest is a deep bowl made of large sticks and twigs, bound with an inner layer of roots, mud, and bark and lined with a softer material, such as deer fur. The nest is usually placed in a large tree or on a cliff ledge, or less frequently in old buildings or utility poles. [4]

Females lay between three and seven pale bluish-green, brown-blotched eggs. Incubation is about 18 to 21 days, by the female only. However, the male may stand or crouch over the young, sheltering but not actually brooding them. Young fledge at 35 to 42 days, and are fed by both parents. They stay with their parents for another six months after fledging. [4]

In most of their range, egg laying begins in late February. In colder climates, it is later, e.g. April in Greenland and Tibet. In Pakistan, egg-laying takes place in December. Eggs and hatchlings are preyed on, rarely, by large hawks and eagles, large owls, martens and canids. The adults, which are very rarely predated, are often successful in defending their young from these predators, due to their numbers, large size and cunning. They have been observed dropping stones on potential predators that venture close to their nests. [4]

Common ravens can be very long-lived, especially in captive or protected conditions; individuals at the Tower of London have lived for more than 40 years. Lifespans in the wild are considerably shorter at typically 10 to 15 years. The longest known lifespan of a banded wild common raven was 23 years, 3 months. [4]

 

References

[1] https://en.wikipedia.org/wiki/Black-billed_magpie

[2] https://en.wikipedia.org/wiki/American_crow

[3] https://en.wikipedia.org/wiki/Northwestern_crow

[4] https://en.wikipedia.org/wiki/Common_raven 

 

Article Images

Background Images

Disclaimer

If you need more information use the form below and contact us.