They leave the nest about 44 days after hatching and begin chasing live insects when they are 49 to 56 days old. Burrowing owls can live for at least nine years in the wild. Large insects such as dragonflies and grasshoppers comprise most of their diet; small mammals like mice, rats, gophers, and ground squirrels are also important.
Other prey animals include reptiles, amphibians, and small birds. THREATS: California's remaining burrowing owls are threatened primarily by habitat loss to urban development, persecution of ground squirrels, and intensive agricultural practices. The state-approved practice of evicting owls from development sites is accelerating local extinction of owls from rapidly urbanizing areas.
Burrowing owls are also at risk of predation from coyotes, birds of prey, and feral cats and dogs. Because of an increase in urban and suburban sprawl, hazards are now consisting of automobiles as well. The scientific name comes from the Greek word athene, referring to the Greek goddess of wisdom whose favorite bird was an owl, and the Latin word cunicularia, meaning a miner or burrower.
Burrowing Owl Facts. DIET: Burrowing Owls primarily feed on insects and small mammals, but they will also eat reptiles and amphibians. They often stand together, very quiet, waiting for the adults and the food. At dusk, they often follow their parents during their foraging trips. The female hunts again when the young are less dependent. They hunt by walking, hopping and running on the ground, but also by flying from a perch, hovering over the vegetation and even flycatching in the air.
They reject pellets including the indigestible parts of the preys. They catch the prey with one foot and transfer it to the bill for carrying it to the nest and feed the young. Little by little, the young owls leave the nest-site and become independent. They will be sexually mature at one year.
The Burrowing Owl is a very pretty bird. This observation was recently done by the authors of all these pictures, in Northern Argentina. Today, it breeds in Alberta and Saskatchewan, with some rare appearances in southwestern Manitoba.
In addition, captive-bred Burrowing Owls breed in and some return to the grasslands near Kamloops, British Columbia, where they are introduced each spring. Today, its range is considerably smaller, particularly in the east. It is now absent from Minnesota, Iowa, the eastern parts of the Dakotas, and south to central Oklahoma and central Texas.
Burrowing Owls that breed in Canada remain on the breeding grounds from April to September. At that time, the prairie owls migrate 2 to 3 km to south Texas and central Mexico, arriving in November. Most British Columbia owls migrate to the west coast from Washington to California; a few spend winter at the inland release sites near Kamloops.
In the south, Burrowing Owls live in agricultural fields, as well as in more open, grassland country, orchards, and even thorn shrub woodlands.
They often hide in burrows, culverts, or open pipes in the daytime, but sometimes they just sit under grass clumps. The owls that journey to summer breeding grounds in Canada begin their migration in late February and early March.
Many Burrowing Owls that breed in Canada do not return. Only half of the adult Burrowing Owls come back to their northern breeding grounds, and a mere 6 percent of young owls return to breed in Canada the year after they are born. Scientists have determined that 40 percent of the young owls die in Canada before they migrate, but they do not know what happens to the rest of the owl population. They are trying to learn whether the owls that do not return are breeding elsewhere or die in winter.
The Burrowing Owl consumes a variety of small creatures. Ground insects, such as grasshoppers and beetles, make up as much as 80 to 90 percent of its diet, but most of its food mass comes from small rodents, such as mice and voles.
It also eats frogs, toads, salamanders, snakes, small birds, and dead animals. Young owls learning to hunt on their own rely mainly on insects for food. They also occasionally scavenge dead animals from roads, and will scurry after insects drawn to warm pavement at night. The Burrowing Owl has several hunting methods, including hunting from a perch such as a mound or fence post, running after insects, hovering close to the ground before pouncing on prey, and using its feet to catch insects in mid-air.
During the summer, with young to feed, the Burrowing Owl hunts around the clock. The male arrives at its summer breeding grounds in Canada first, in April, and selects a burrow that has been abandoned by badgers or other ground-dwelling mammals.
The female arrives shortly afterwards. The owls spend the first two weeks performing elaborate territorial and courtship displays that include flashing white markings, cooing, bowing, scratching, nipping, stretching, and repeated short flights, and the male attracts the female using its coo-cooo call. Generally, the birds do not pair for life, although some pairs may reunite for a second summer. Burrows are important for protection from weather and predators, for raising young, and for controlling temperature.
Although the Burrowing Owl does not dig its burrow, it may remove blockages in the tunnel or widen the passage. The male lines the tunnel and nest chamber with dried plants, feathers, and dry, shredded cow manure. This lining may help to keep the burrow cool during the day and warm at night, helping to incubate the eggs. After arranging the nest, the male rarely enters the burrow, but he provides food for the female, who stays underground to incubate the eggs and brood the young.
The male lives in a nearby burrow. When Burrowing Owls were more numerous, they nested in burrows that were part of a loose colony. Now, burrows are often isolated. A Burrowing Owl can breed the summer after it hatches and every summer after that. In Canada, the female lays 4 to 12, and on average 9, white eggs that eventually stain a brownish colour from the nest material.
The female incubates the eggs for about four weeks, with the eggs hatching in the order in which they were laid. The Burrowing Owl lays more eggs than it can raise in most years. On average, of the nine eggs laid, one will not hatch, while three to six young will not fledge, or reach the stage where they are capable of flying.
Most nestlings die from starvation; the males are unable to provide enough food to keep all the young alive during their first two to three weeks. Cannibalism of young is also common during natural food shortages. The female helps provide food when the young no longer require brooding. The hatchlings stay underground for two to three weeks. By early to mid-June, downy young appear at the burrow opening.
At around four weeks, some of the young owls move to nearby burrows, where they wait at the entrances for the adults to feed them. This allows for even food distribution among the young, avoids crowding, and lessens the chance of a predator killing the entire group. Young owls are capable of short flights in early July, and, by about seven weeks of age, they can make sustained flights.
They learn to hunt on their own at about seven or eight weeks. By the time they are nine or 10 weeks old, the young have become independent, in time for the beginning of the southward migration in mid-September. On rare occasions, a Burrowing Owl may live as long as eight years. At one time, the Burrowing Owl was common in the four western Canadian provinces. Now, it is one of the most endangered birds in these areas.
The decline in population began in the s and accelerated during the s to an average rate of 22 percent a year. In , more than 2 breeding pairs of Burrowing Owls lived in Canada; by , the number of pairs had dropped to fewer than 1 Human activity has a great impact on the Burrowing Owl.
Chemical pesticides, applied to control ground squirrels and grasshoppers, sometimes poison the Burrowing Owl. For example, carbofuran, a pesticide that is now banned, was linked to a reduction in the number of young Burrowing Owls. Strychnine-covered grain has also killed owls that eat the grain that is left in burrows to kill ground squirrels.
Pesticides also kill animals and insects that the Burrowing Owl eats. This may force the bird to hunt far from the safety of its nesting site, making it more susceptible to predators and other dangers.
Fewer of these digging animals means fewer nests and nearby roost, or resting, burrows for the birds. Burrowing Owls sometimes die along roads. Young owls in particular hunt on and beside roads at night. Because they are slow flyers and have difficulty escaping oncoming traffic, they are often killed.
Habitat loss and changes in the quality of habitat reduce hunting and nesting territories and are associated with low birth and high death rates among Burrowing Owls. In Canada, less than 24 percent of the original prairie habitat remains. The Burrowing Owl has many natural predators.
Badgers, foxes, skunks, weasels, raccoons, and snakes dig up or enter burrows, eating eggs, nestlings, or adult females; other owls, hawks, falcons, domestic cats and dogs, and coyotes prey upon adults and young outside the burrow.
A national Burrowing Owl recovery team, working through a program that includes governmental and non-governmental groups, approved a recovery plan in and updated the plan in This plan aims to increase Burrowing Owl populations in Canada to levels where they can sustain themselves. In addition, the recovery team members are involved in the experimental release of captive-bred owls in Saskatchewan and the reintroduction of owls in British Columbia.
Few of the birds released in Saskatchewan have returned there. Some of the more than birds introduced into the Kamloops region of British Columbia since the program began in have mated and produced young, and a few have returned to British Columbia the following spring. Despite its efforts, the recovery team has not been able to identify the key factors behind the population decline, although research has shown that some combination of factors is to blame.
To help it reach some conclusions, the team is working to gather information about migration, winter range, changes on the breeding grounds, mortality, and the effects of various land uses on the owl. One of the reasons assembling this knowledge is taking time is because Burrowing Owls are difficult to track. They are very cryptic, or hard to see because of coloration that camouflages them. They migrate at night and fly alone, not in flocks.
In addition, because of their small size, they cannot carry satellite transmitters like those used on larger birds, making it necessary for biologists to attach smaller radio transmitters with shorter ranges. Through two nongovernmental programs alone—Operation Burrowing Owl in Saskatchewan, which began in , and Operation Grassland Community in Alberta, which started in —more than landowners have conserved roughly 70 hectares of Burrowing Owl nesting habitat.
Audubon Field Guide, Burrowing Owl. Print resources Alcorn, G. Owls: An introduction for the amateur naturalist. Prentice Hall, New York. Eckert, A. The owls of North America. First edition. Weathervane Books, New York. Godfrey, W. Birds of Canada. Revised edition. National Museum of Natural Sciences, Ottawa. Haug, E. Millsap, and M. Burrowing Owl Speotyto cunicularia. Poole and F. Gill, editors.
0コメント