Natural History Information From the Burrowing Owl Studbook:
Range and Habitat
Burrowing owls are distributed in the southern regions of the Canadian provinces of Manitoba, Saskatchewan and Alberta. The species has been recently reintroduced into British Columbia where it had been extirpated. In the United States, there is an isolated population in Florida while the majority resides in the western part of the country; from the Canadian to the Mexican borders and from California to the extreme western portions of Minnesota and Iowa. The species is also located in suitable habitat throughout Central and South America and on the islands of Cuba, Hispaniola, the northern Lesser Antilles, Bahamas, Guadalupe and Clarion.
During the winter, the species vacates the northern areas of the Great Plains and Great Basin. Populations as far south as northern New Mexico and Arizona migrate although there are scattered records of wintering as far north as Montana. Migration south occurs in September-October and north in March - May. Based on banding recoveries, it is theorized that the Canadian owls migrate further south than those from the United States in a leap-frog migration. In the United States, California is the most important state for over-wintering, followed by New Mexico, Florida, Arizona, Mexico, Texas and Louisiana.
The species is limited to open country with short vegetation: well-drained grasslands, steppes, deserts and prairies. Although a few specimens have been seen in montane regions, there has been no known nesting in these areas. Populations are often associated with burrowing mammals. Burrowing owls are adaptable to human habitation and can be found in agricultural areas as well as golf courses, cemeteries, road allowances, airports, vacant lots in residential areas, fairgrounds and college campuses. The availability of a nest burrow is an essential requirement for the Western burrowing owl. In Florida, where the owls can dig their own burrows, burrowing animals are not essential.
Burrowing owls are distributed in the southern regions of the Canadian provinces of Manitoba, Saskatchewan and Alberta. The species has been recently reintroduced into British Columbia where it had been extirpated. In the United States, there is an isolated population in Florida while the majority resides in the western part of the country; from the Canadian to the Mexican borders and from California to the extreme western portions of Minnesota and Iowa. The species is also located in suitable habitat throughout Central and South America and on the islands of Cuba, Hispaniola, the northern Lesser Antilles, Bahamas, Guadalupe and Clarion.
During the winter, the species vacates the northern areas of the Great Plains and Great Basin. Populations as far south as northern New Mexico and Arizona migrate although there are scattered records of wintering as far north as Montana. Migration south occurs in September-October and north in March - May. Based on banding recoveries, it is theorized that the Canadian owls migrate further south than those from the United States in a leap-frog migration. In the United States, California is the most important state for over-wintering, followed by New Mexico, Florida, Arizona, Mexico, Texas and Louisiana.
The species is limited to open country with short vegetation: well-drained grasslands, steppes, deserts and prairies. Although a few specimens have been seen in montane regions, there has been no known nesting in these areas. Populations are often associated with burrowing mammals. Burrowing owls are adaptable to human habitation and can be found in agricultural areas as well as golf courses, cemeteries, road allowances, airports, vacant lots in residential areas, fairgrounds and college campuses. The availability of a nest burrow is an essential requirement for the Western burrowing owl. In Florida, where the owls can dig their own burrows, burrowing animals are not essential.
Physical Description
The burrowing owl is a small ground-dwelling owl; length varies from 19.0 to 25 cm and the average weight is 150 g. The largest specimens are found in western North America and southern South America. The Caribbean population, including Florida, is intermediate in size and the smallest specimens are nearest the equator. The head is round and lacks ear tufts. The facial disc, which is poorly developed, is framed by a broad, buffy-white stripe on the interior part from the eyebrow to the cheek. This stripe is fully exposed when the owl is in the white and tall posture seen during territorial disputes and copulatory behaviors. The characteristic long legs are lightly feathered with short, fine plumage. The toes, which are not especially powerful in gripping, are almost bare with small, very bristly feathers. In flight, the burrowing owl is highly maneuverable.
The burrowing owl is only slightly dimorphic. On average, males have longer tails, weigh 8 grams more and have a 3 - 4 mm greater wing span than females. Females generally have more barring on the breast and are darker than males. This is especially apparent immediately proceeding the postnuptial molt.
The burrowing owl is a small ground-dwelling owl; length varies from 19.0 to 25 cm and the average weight is 150 g. The largest specimens are found in western North America and southern South America. The Caribbean population, including Florida, is intermediate in size and the smallest specimens are nearest the equator. The head is round and lacks ear tufts. The facial disc, which is poorly developed, is framed by a broad, buffy-white stripe on the interior part from the eyebrow to the cheek. This stripe is fully exposed when the owl is in the white and tall posture seen during territorial disputes and copulatory behaviors. The characteristic long legs are lightly feathered with short, fine plumage. The toes, which are not especially powerful in gripping, are almost bare with small, very bristly feathers. In flight, the burrowing owl is highly maneuverable.
The burrowing owl is only slightly dimorphic. On average, males have longer tails, weigh 8 grams more and have a 3 - 4 mm greater wing span than females. Females generally have more barring on the breast and are darker than males. This is especially apparent immediately proceeding the postnuptial molt.
Life Cycle
Burrowing owls are predominantly monogamous but polygamy has been observed in Saskatchewan. Both sexes can breed at one year of age. Pairs are sometimes maintained in non-migratory populations. Migratory birds may return to the breeding area paired or unpaired. During pair formation, the male will court several females with his primary song and displays. While singing, the male will bend forward, almost parallel to the ground with his primaries and secondaries held together over his back and white patches of the throat and brow fully displayed. Other courtship behaviors include circular flights, billing and preening of the head and face, and the male presenting food to the female. Parent-offspring pairings are not uncommon in some areas.
Copulation is done at the burrow, most often at dusk. The female will move towards or away from the singing male at the start of copulatary behavior. The male will then stop singing, stand and look down at the female with white patches exposed and feathers raised. The female will stand erect with exposed white patches. The male will then fly to the female and mount her, giving the primary call with or without the male warble and may terminate with a tweeter call. The male flaps his wings while mounted, probably for balance. He may scratch the female’s head and both may bill nip. Copulation lasts 4 - 6 seconds and is done 1 - 3 times per evening.
The burrowing owl has the largest clutch size of any North American raptor, laying up to 12 eggs. The eggs are white when laid but soon become covered with flea excrement. The female alone incubates the eggs for 28 - 30 days. In some areas, incubation starts after the first egg is laid while in others, it does not begin until the clutch is complete. During this period, the male feeds the female during the early morning and evening and
stays within 250 m of the nest burrow during the day. The burrowing owls in Florida have been known to double clutch. The western owls may lay a smaller second clutch if the first is destroyed early in the breeding season and very rarely produce a second brood.
Studies have found mean brood sizes from 2.7 in Wyoming to 4.9 in New Mexico. There is no known correlation between nest success and size of parents or physical attributes of the burrow. There is evidence that the reproductive success is low when the diet does not contain any vertebrates while raising young.
Burrowing owls are predominantly monogamous but polygamy has been observed in Saskatchewan. Both sexes can breed at one year of age. Pairs are sometimes maintained in non-migratory populations. Migratory birds may return to the breeding area paired or unpaired. During pair formation, the male will court several females with his primary song and displays. While singing, the male will bend forward, almost parallel to the ground with his primaries and secondaries held together over his back and white patches of the throat and brow fully displayed. Other courtship behaviors include circular flights, billing and preening of the head and face, and the male presenting food to the female. Parent-offspring pairings are not uncommon in some areas.
Copulation is done at the burrow, most often at dusk. The female will move towards or away from the singing male at the start of copulatary behavior. The male will then stop singing, stand and look down at the female with white patches exposed and feathers raised. The female will stand erect with exposed white patches. The male will then fly to the female and mount her, giving the primary call with or without the male warble and may terminate with a tweeter call. The male flaps his wings while mounted, probably for balance. He may scratch the female’s head and both may bill nip. Copulation lasts 4 - 6 seconds and is done 1 - 3 times per evening.
The burrowing owl has the largest clutch size of any North American raptor, laying up to 12 eggs. The eggs are white when laid but soon become covered with flea excrement. The female alone incubates the eggs for 28 - 30 days. In some areas, incubation starts after the first egg is laid while in others, it does not begin until the clutch is complete. During this period, the male feeds the female during the early morning and evening and
stays within 250 m of the nest burrow during the day. The burrowing owls in Florida have been known to double clutch. The western owls may lay a smaller second clutch if the first is destroyed early in the breeding season and very rarely produce a second brood.
Studies have found mean brood sizes from 2.7 in Wyoming to 4.9 in New Mexico. There is no known correlation between nest success and size of parents or physical attributes of the burrow. There is evidence that the reproductive success is low when the diet does not contain any vertebrates while raising young.
CHICKS
Burrowing owl chicks are altricial, weigh approximately 8.9 upon hatching and are partially covered with down. The eyes open on day 5 when the chicks also start exhibiting evasive behavior and producing the rattlesnake buzz when the nest is disturbed. On day 9, the egg tooth sloughs off.
During brooding, the adult male supplies all the food for the female and chicks. The female will start hunting as the young become less dependent. If the female dies, males of the western race may feed the chicks. Males in Florida have never been seen feeding chicks.
The chicks first emerge from the burrow at 10 - 21 days of age and stay cautiously near the entrance. After one week they can be seen running about flapping their wings but still stay close to the burrow. Four weeks after emergence they can fly well but remain within 50 m of the burrow. At this time they are foraging independently. By 8 - 9 weeks of age, the chicks are gathering the majority of their own food. Ten week old owlets are not easily distinguished from adults.
Burrowing owl chicks are altricial, weigh approximately 8.9 upon hatching and are partially covered with down. The eyes open on day 5 when the chicks also start exhibiting evasive behavior and producing the rattlesnake buzz when the nest is disturbed. On day 9, the egg tooth sloughs off.
During brooding, the adult male supplies all the food for the female and chicks. The female will start hunting as the young become less dependent. If the female dies, males of the western race may feed the chicks. Males in Florida have never been seen feeding chicks.
The chicks first emerge from the burrow at 10 - 21 days of age and stay cautiously near the entrance. After one week they can be seen running about flapping their wings but still stay close to the burrow. Four weeks after emergence they can fly well but remain within 50 m of the burrow. At this time they are foraging independently. By 8 - 9 weeks of age, the chicks are gathering the majority of their own food. Ten week old owlets are not easily distinguished from adults.
MORTALITY
Nest failure can be caused by flash flooding, death of the female, burrow destruction by agriculture, fumigation and predation on nesting adults or eggs by snakes, badgers or skunks. The most important cause of mortality for fledglings is predation by mammals, large raptors and snakes. Starvation due to inexperienced hunting is not uncommon and disease, poisoning and heavy parasite loads are also causes of fledgling deaths.
Collisions with vehicles are a significant cause of death for younger adults. Adults are also killed by shooting and indirect and direct poisoning.
One study found the survival rate for juveniles to be 30%, while 81% of adults survived.
BehaviorBurrowing owls are primarily active during dusk and in the early morning hours, although they will hunt throughout the day and night, especially if they have young to feed. They'll use their sense of hearing rather than sight. They chase down grasshoppers and beetles on the ground, or they use their talons to catch large insects in the air. When disturbed, burrowing owls will flatten itself against the ground rather than fly away. When angry or irritated, an owl will express its displeasure by clacking its bill.
Birds living in the northern US and Canada are migratory.
Nest failure can be caused by flash flooding, death of the female, burrow destruction by agriculture, fumigation and predation on nesting adults or eggs by snakes, badgers or skunks. The most important cause of mortality for fledglings is predation by mammals, large raptors and snakes. Starvation due to inexperienced hunting is not uncommon and disease, poisoning and heavy parasite loads are also causes of fledgling deaths.
Collisions with vehicles are a significant cause of death for younger adults. Adults are also killed by shooting and indirect and direct poisoning.
One study found the survival rate for juveniles to be 30%, while 81% of adults survived.
BehaviorBurrowing owls are primarily active during dusk and in the early morning hours, although they will hunt throughout the day and night, especially if they have young to feed. They'll use their sense of hearing rather than sight. They chase down grasshoppers and beetles on the ground, or they use their talons to catch large insects in the air. When disturbed, burrowing owls will flatten itself against the ground rather than fly away. When angry or irritated, an owl will express its displeasure by clacking its bill.
Birds living in the northern US and Canada are migratory.
Communication
Adult burrowing owls produce a primary call, 5 calls that are associated with copulation and 7 associated with nest defense and/or food begging. The coo-coo or primary call is given only by the male and can be heard during pair formation, precopulatory behavior and territory defense. Other calls associated with copulation are the female’s smack and eep, the male’s tweeter and copulation song, and a warble that is used by both sexes. The female’s rasp appears to stimulate the male to begin foraging. It is also given by the female during times of distress, when receiving food or when giving food to chicks. Other calls include the chuck, chatter and scream which are given by both sexes during nest defense.
Juveniles produce a low intensity alarm call or eep that may also be a hunger call. The juvenile rasp, like the female’s, stimulates the adult male to begin foraging. The rattlesnake rasp , which may also be produced by adult females, is given during severe distress when the juvenile is in the burrow. A low-level protest or threat display is conveyed by a snap.
Adult burrowing owls produce a primary call, 5 calls that are associated with copulation and 7 associated with nest defense and/or food begging. The coo-coo or primary call is given only by the male and can be heard during pair formation, precopulatory behavior and territory defense. Other calls associated with copulation are the female’s smack and eep, the male’s tweeter and copulation song, and a warble that is used by both sexes. The female’s rasp appears to stimulate the male to begin foraging. It is also given by the female during times of distress, when receiving food or when giving food to chicks. Other calls include the chuck, chatter and scream which are given by both sexes during nest defense.
Juveniles produce a low intensity alarm call or eep that may also be a hunger call. The juvenile rasp, like the female’s, stimulates the adult male to begin foraging. The rattlesnake rasp , which may also be produced by adult females, is given during severe distress when the juvenile is in the burrow. A low-level protest or threat display is conveyed by a snap.
ACTIVITY PATTERN
The daily activity pattern of the burrowing owl varies during the year. They tend to be more nocturnal during the winter and more diurnal in the summer. In the spring, before nesting, the owls are inactive in the late morning and early afternoon. Reproductive behavior occurs in the late evening and foraging throughout the night and early morning. During incubation the males stay near the burrows during the day and forage away for the burrows after dusk. When the chicks fledge, both sexes increase their diurnal activity. After nesting, the birds are active mainly after sundown, spending the daylight hours in burrows or other roosts. During the spring and fall, the amount of diurnal versus nocturnal activity is dependent in part on insect densities. Ambient temperature also affects the pattern of activity; above 410 C, there is a decrease in diurnal activity and a resulting increase in nocturnal activity.
The daily activity pattern of the burrowing owl varies during the year. They tend to be more nocturnal during the winter and more diurnal in the summer. In the spring, before nesting, the owls are inactive in the late morning and early afternoon. Reproductive behavior occurs in the late evening and foraging throughout the night and early morning. During incubation the males stay near the burrows during the day and forage away for the burrows after dusk. When the chicks fledge, both sexes increase their diurnal activity. After nesting, the birds are active mainly after sundown, spending the daylight hours in burrows or other roosts. During the spring and fall, the amount of diurnal versus nocturnal activity is dependent in part on insect densities. Ambient temperature also affects the pattern of activity; above 410 C, there is a decrease in diurnal activity and a resulting increase in nocturnal activity.
DIET & FOOD COLLECTION
The composition of the burrowing owl’s diet changes over the course of the year in accordance with prey abundance and stage of nesting. They are highly opportunistic feeders, primarily eating arthropods and small mammals. Birds are also taken but are usually not a significant part of the diet expect during the prey species’ nesting season. In Florida, reptiles and amphibians may also be important components of the diet. Carrion is occasionally eaten as are small amounts of vegetations. Many researchers have found a significant decline in the percentage of vertebrate prey and a comparative increase in invertebrate prey during the breeding season.
Burrowing owls have been observed hunting at all times of the day but are primarily crepuscular in their foraging habits. Insects are most often taken during daylight and small mammals more often after dark.
Burrowing owls employ four methods to capture prey: ground foraging, hunting from a perch, hovering and fly-catching. Ground foraging is the primary means for hunting used by both sexes, and it occurs most frequently at mid-day and always in areas of short (>20 cm) vegetation. The bird runs or hops across the ground stopping and turning its head frequently. When prey is detected, the owl pounces on it from a distance of .5 - 1 meter. If prey is detected when hunting from a perch, the owl flies a short distance and tries to land directly on it. If unsuccessful, the owl will pursue the prey as in ground foraging. Males use this method more than females. During hovering, the males (females are rarely seen using this method) will hover vertically for several seconds, then drop 3 - 4.5 m and fly horizontally 45 - 70 m and then return to their initial altitude. This is repeated 10 - 15 times or until a capture is made. Hovering is often seen over tall vegetation. Fly-catching is used to capture insects in flight and is the least utilized hunting method.
Some researchers suggest that burrowing owls line their nests with dung as a tool to lure beetles. One test showed that taking the dung away from the burrows’ entrances left owls with few beetles in their diet. After adding cow-dung, owls averaged ten times as many beetle meals as during the test.
Prey is caught with the talons and may be transferred to the beak for transport or presentation to young. The upper limit for a prey item has been estimated at 115 g. Storing food, usually at the burrow entrance, is not uncommon while caching food away from the burrow is rarely seen. An adult needs 15.5 +/- 1.86 kcal/d but there are records of birds fasting for several days while over-wintering in northern latitudes.
The composition of the burrowing owl’s diet changes over the course of the year in accordance with prey abundance and stage of nesting. They are highly opportunistic feeders, primarily eating arthropods and small mammals. Birds are also taken but are usually not a significant part of the diet expect during the prey species’ nesting season. In Florida, reptiles and amphibians may also be important components of the diet. Carrion is occasionally eaten as are small amounts of vegetations. Many researchers have found a significant decline in the percentage of vertebrate prey and a comparative increase in invertebrate prey during the breeding season.
Burrowing owls have been observed hunting at all times of the day but are primarily crepuscular in their foraging habits. Insects are most often taken during daylight and small mammals more often after dark.
Burrowing owls employ four methods to capture prey: ground foraging, hunting from a perch, hovering and fly-catching. Ground foraging is the primary means for hunting used by both sexes, and it occurs most frequently at mid-day and always in areas of short (>20 cm) vegetation. The bird runs or hops across the ground stopping and turning its head frequently. When prey is detected, the owl pounces on it from a distance of .5 - 1 meter. If prey is detected when hunting from a perch, the owl flies a short distance and tries to land directly on it. If unsuccessful, the owl will pursue the prey as in ground foraging. Males use this method more than females. During hovering, the males (females are rarely seen using this method) will hover vertically for several seconds, then drop 3 - 4.5 m and fly horizontally 45 - 70 m and then return to their initial altitude. This is repeated 10 - 15 times or until a capture is made. Hovering is often seen over tall vegetation. Fly-catching is used to capture insects in flight and is the least utilized hunting method.
Some researchers suggest that burrowing owls line their nests with dung as a tool to lure beetles. One test showed that taking the dung away from the burrows’ entrances left owls with few beetles in their diet. After adding cow-dung, owls averaged ten times as many beetle meals as during the test.
Prey is caught with the talons and may be transferred to the beak for transport or presentation to young. The upper limit for a prey item has been estimated at 115 g. Storing food, usually at the burrow entrance, is not uncommon while caching food away from the burrow is rarely seen. An adult needs 15.5 +/- 1.86 kcal/d but there are records of birds fasting for several days while over-wintering in northern latitudes.
INTRASPECIFIC BEHAVIOR AND TERRITORIALITY
Burrowing owls have three types of social groupings: solitary birds, one breeding pair and a concentration of birds. Colonies consist of 9 -19 birds and there is no complex social order. Colonies break up after the chicks are grown and the owls become nomadic. Migrants are solitary during the winter.
Burrowing owls are only territorial during the mating season. The size of protected territories may vary with the concentration of nesting pairs. One study found an average of 166 m between neighboring active burrows and another found an increase in nest desertion when the distance was less than 109 m. Males establish and maintain territories which include the burrows and surrounding area. The vertical space is only occasionally protected. Territories are defended by the males using the primary call and presenting himself to intruders. Physical contact is used only if an intruder is within 10 m of the burrow.
INTERSPECIFIC BEHAVIOR
During the nesting season, burrowing owls will attack mammalian predators which include coyotes, foxes, badgers, raccoons, skunks, weasels and small rodents. Avian predators which include Swainson’s and Ferruginous hawks, prairie falcons, great horned owls and northern harriers, elicit escape behavior. Burrowing owls are often harassed by songbirds as potential enemies and they respond by escaping to a perch or burrow.
Burrowing owls have three types of social groupings: solitary birds, one breeding pair and a concentration of birds. Colonies consist of 9 -19 birds and there is no complex social order. Colonies break up after the chicks are grown and the owls become nomadic. Migrants are solitary during the winter.
Burrowing owls are only territorial during the mating season. The size of protected territories may vary with the concentration of nesting pairs. One study found an average of 166 m between neighboring active burrows and another found an increase in nest desertion when the distance was less than 109 m. Males establish and maintain territories which include the burrows and surrounding area. The vertical space is only occasionally protected. Territories are defended by the males using the primary call and presenting himself to intruders. Physical contact is used only if an intruder is within 10 m of the burrow.
INTERSPECIFIC BEHAVIOR
During the nesting season, burrowing owls will attack mammalian predators which include coyotes, foxes, badgers, raccoons, skunks, weasels and small rodents. Avian predators which include Swainson’s and Ferruginous hawks, prairie falcons, great horned owls and northern harriers, elicit escape behavior. Burrowing owls are often harassed by songbirds as potential enemies and they respond by escaping to a perch or burrow.
BURROWS
Burrowing owls can dig their own burrows in loose soil but most often use existing burrows made by prairie dogs, badgers, ground squirrels, marmots, viscachas, wolves, foxes, skunks, armadillos or other burrowing animals. They are opportunistic when natural burrows are not available, using irrigation pipes, buried cars, etc. Burrows sites are ideally located in areas of low vegetation (under 10 cm) and near perches (usually have 2 within 35 - 80 m of burrow entrance).
Both members of a breeding pair will renovate and maintain the burrow by standing on one leg and flinging the substrate back with a few strokes of the other leg. The opposite wing may be extended for support and the beak may be used as well. Males and females have been seen digging with equal frequency but females worked longer. The pair may work on several burrows at first and then concentrate on one.
Burrow sizes and shapes are dependent upon the species that first excavated them.
After renovation of prairie dog burrows by owls in the Oklahoma panhandle, the tunnels averaged 14 - 15cm wide by 11 ½ - 13 cm high. The nest chambers were circular or oblong; and averaged 25 cm wide by 10 - 15 cm high, 70 cm below ground surface and 150 cm from the tunnel entrance.
All burrows have at least one turn to keep the nest chamber in darkness and a mound of soil at the entrance. The tunnel and nest chamber are lined with shredded cow or horse dung throughout most of the breeding season. The dung may be used as insulation, to absorb moisture, attract beetles and/or to mask the smell of the owls.
Satellite burrows may be used by adults and chicks for protection from inclement weather or predators. Burrows are used and maintained year round by non-migratory populations.
The temperature in the burrow is the same from entrance to the depth but the amount of water vapor in the air increases which decreases the amount of water the owls lose through evaporation. As an adaptation to living underground, the burrowing owl can survive in higher concentrations of carbon dioxide than other birds.
Burrowing owls can dig their own burrows in loose soil but most often use existing burrows made by prairie dogs, badgers, ground squirrels, marmots, viscachas, wolves, foxes, skunks, armadillos or other burrowing animals. They are opportunistic when natural burrows are not available, using irrigation pipes, buried cars, etc. Burrows sites are ideally located in areas of low vegetation (under 10 cm) and near perches (usually have 2 within 35 - 80 m of burrow entrance).
Both members of a breeding pair will renovate and maintain the burrow by standing on one leg and flinging the substrate back with a few strokes of the other leg. The opposite wing may be extended for support and the beak may be used as well. Males and females have been seen digging with equal frequency but females worked longer. The pair may work on several burrows at first and then concentrate on one.
Burrow sizes and shapes are dependent upon the species that first excavated them.
After renovation of prairie dog burrows by owls in the Oklahoma panhandle, the tunnels averaged 14 - 15cm wide by 11 ½ - 13 cm high. The nest chambers were circular or oblong; and averaged 25 cm wide by 10 - 15 cm high, 70 cm below ground surface and 150 cm from the tunnel entrance.
All burrows have at least one turn to keep the nest chamber in darkness and a mound of soil at the entrance. The tunnel and nest chamber are lined with shredded cow or horse dung throughout most of the breeding season. The dung may be used as insulation, to absorb moisture, attract beetles and/or to mask the smell of the owls.
Satellite burrows may be used by adults and chicks for protection from inclement weather or predators. Burrows are used and maintained year round by non-migratory populations.
The temperature in the burrow is the same from entrance to the depth but the amount of water vapor in the air increases which decreases the amount of water the owls lose through evaporation. As an adaptation to living underground, the burrowing owl can survive in higher concentrations of carbon dioxide than other birds.
Threats and Conservation Status
Two burrowing owl races from the West Indies have become extinct in historical times: A.c. amaura of Antigue Island, Nevis Island and St Christopher Island; and A.c. guadeloupenis of Marie Galante Island. Both became extinct at the end of the 19th century shortly after the introduction of the mongoose.
The burrowing owl is not currently listed by the USDI. In 2002, the species was added to the United States Fish and Wildlife Service’s Birds of Conservation Concern. The list is meant to “accurately identify the bird species that represent the agencies highest conservation priorities and draw attention to species in need of conservation action”. It was previously listed as a Category II Candidate Species meaning there is concern about the species’ status but not enough information to make a more definite listing. The species was previously listed as rare from 1966 - 1968 and undetermined in 1973. It is listed as endangered in Minnesota and Iowa, and as a Species of Special Concern in California, Washington, Oregon, Montana, Wyoming, Florida, Idaho, Oklahoma, South Dakota and Utah. NatureServe Explorer (www.natureserve.org/explorer), lists the species as:
Mexico listed the species as threatened in 1994. There is little information on the status of the species in Central or South America. Decreasing populations have been noted in Argentina, Brazil, Chile and Uraguay.
Two burrowing owl races from the West Indies have become extinct in historical times: A.c. amaura of Antigue Island, Nevis Island and St Christopher Island; and A.c. guadeloupenis of Marie Galante Island. Both became extinct at the end of the 19th century shortly after the introduction of the mongoose.
The burrowing owl is not currently listed by the USDI. In 2002, the species was added to the United States Fish and Wildlife Service’s Birds of Conservation Concern. The list is meant to “accurately identify the bird species that represent the agencies highest conservation priorities and draw attention to species in need of conservation action”. It was previously listed as a Category II Candidate Species meaning there is concern about the species’ status but not enough information to make a more definite listing. The species was previously listed as rare from 1966 - 1968 and undetermined in 1973. It is listed as endangered in Minnesota and Iowa, and as a Species of Special Concern in California, Washington, Oregon, Montana, Wyoming, Florida, Idaho, Oklahoma, South Dakota and Utah. NatureServe Explorer (www.natureserve.org/explorer), lists the species as:
- apparently secure: United States, Colorado, New Mexico
- vulnerable: Arizona, Kansas, Montana, Nebraska, Nevada, Oregon, South Dakota, Texas, Utah, Wyoming
- imperiled: Canada, Alberta, Saskatchewan, California, Oklahoma, Washington
- critically imperiled: British Columbia, Manitoba, Minnesota
- unranked: Florida, North Dakota
Mexico listed the species as threatened in 1994. There is little information on the status of the species in Central or South America. Decreasing populations have been noted in Argentina, Brazil, Chile and Uraguay.
CAUSES OF DECLINE
The burrowing owl has adapted well to close human presence and even benefits from some environmental changes caused by humans, i.e., cattle grazing, mowing, deforestation and wetland drainage. One study in Florida found the species did better in areas with 54 - 60% development but that any further increase in development was detrimental.
The widespread control of burrowing mammals is a leading cause of decline for the burrowing owl. Of the 700,000,000 acres of prairie dog habitat that existed in 1900, less than 2,000,000 exist today. In 2000, the USFWS ruled that the black-tailed prairie dog was “warranted but precluded” for protection under the Endangered Species Act. The extermination of the yellow badger from British Columbia was the major cause of the owl’s extinction in that province.
Direct habitat loss to urban, industrial and agricultural development is also a major cause of decline. In central California, 65% of burrowing owl breeding habitat has disappeared in the last 10 years.
Poisoning, directly or indirectly, also adversely affects the wild population. One study found a 54% decrease in young/nest and a 50% decrease in proportion of pairs that raised 1 or more young when carbofuran (Furadan) was sprayed within 5 m of nest burrows. Poisoning also decreases the availability of prey which has been shown to decrease the size and number of eggs laid by burrowing owls.
Although vehicular traffic does not seem to affect the reproductive success of pairs nesting near highways, collisions with vehicles is a major cause of mortality. Other manmade sources of mortality include the introduction of domestic cats and dogs into owl habitat and shooting.
The burrowing owl has adapted well to close human presence and even benefits from some environmental changes caused by humans, i.e., cattle grazing, mowing, deforestation and wetland drainage. One study in Florida found the species did better in areas with 54 - 60% development but that any further increase in development was detrimental.
The widespread control of burrowing mammals is a leading cause of decline for the burrowing owl. Of the 700,000,000 acres of prairie dog habitat that existed in 1900, less than 2,000,000 exist today. In 2000, the USFWS ruled that the black-tailed prairie dog was “warranted but precluded” for protection under the Endangered Species Act. The extermination of the yellow badger from British Columbia was the major cause of the owl’s extinction in that province.
Direct habitat loss to urban, industrial and agricultural development is also a major cause of decline. In central California, 65% of burrowing owl breeding habitat has disappeared in the last 10 years.
Poisoning, directly or indirectly, also adversely affects the wild population. One study found a 54% decrease in young/nest and a 50% decrease in proportion of pairs that raised 1 or more young when carbofuran (Furadan) was sprayed within 5 m of nest burrows. Poisoning also decreases the availability of prey which has been shown to decrease the size and number of eggs laid by burrowing owls.
Although vehicular traffic does not seem to affect the reproductive success of pairs nesting near highways, collisions with vehicles is a major cause of mortality. Other manmade sources of mortality include the introduction of domestic cats and dogs into owl habitat and shooting.
CONSERVATION EFFORTS
The Canadian National Burrowing Owl Recovery Plan prepared in 1990 identified four conservation priorities:
The El Paso Zoo instituted a relocation program in 2007 and the Assinbione Zoo in Winnipeg is currently breeding owls for release.
Other proposed conservation methods include protecting burrowing mammal populations, placing artificial perches in suitable habitat, burning vegetation. The effectiveness of most methods implemented has not been measured.
Prejudices against birds of prey still persist among many who wrongly believe that they harm wildlife or present major threats to domestic animals. Biological studies have documented their ecological importance as major controls on rodent populations. Some birds of prey feed on snakes, insects or other potential pests. No species of raptor poses a significant threat to domestic animals.
Instruct guests to never litter, especially when they are in a car. Throwing trash out along the roads not only makes the roads less attractive, but can also attract animals to the sides of the road. Some of these animals might look appetizing to an owl, hawk, or other predator which are then more likely to be hit by passing vehicles.
Did you know…
The Canadian National Burrowing Owl Recovery Plan prepared in 1990 identified four conservation priorities:
- Priority 1: decrease mortality and increase productivity on breeding grounds and protect and manage nesting habitat
- Priority 2: monitor population and population management on migration and wintering grounds
- Priority 3: eliminate negative effects of pesticides
- Priority 4: release programs.
The El Paso Zoo instituted a relocation program in 2007 and the Assinbione Zoo in Winnipeg is currently breeding owls for release.
Other proposed conservation methods include protecting burrowing mammal populations, placing artificial perches in suitable habitat, burning vegetation. The effectiveness of most methods implemented has not been measured.
Prejudices against birds of prey still persist among many who wrongly believe that they harm wildlife or present major threats to domestic animals. Biological studies have documented their ecological importance as major controls on rodent populations. Some birds of prey feed on snakes, insects or other potential pests. No species of raptor poses a significant threat to domestic animals.
Instruct guests to never litter, especially when they are in a car. Throwing trash out along the roads not only makes the roads less attractive, but can also attract animals to the sides of the road. Some of these animals might look appetizing to an owl, hawk, or other predator which are then more likely to be hit by passing vehicles.
Did you know…
- Like other owl species, burrowing owls can turn their heads almost 270 degrees. This movement is an adaptation because owls' eyes cannot move in their sockets like other animals.
- They have an inner eyelid to shield sensitive retina from sunlight, and to protect against air and dust during flight.
- The burrowing owl has also been known as ground owl, prairie dog owl, rattlesnake owl, howdy owl, cuckoo owl, tunnel owl, gopher owl, and hill owl.
- The first published report of the burrowing owl was by an Italian Jesuit priest stationed in Chile. His description appeared in a book he wrote on the natural history of the country in 1782. The Latin word cunicularius means mine, or miner - an apt description for a bird that makes its home beneath the ground.
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Date of Last PVA/B&T Plan
9/2019; MateRx 9/26/17 B&T plan scheduled Current Population Size (N) 149 Current Number of Participating AZA Member Institutions 43 Projected % GD at 100 years or 10 generations** 57% |
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Officers
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Name
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Organization
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Position
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San Diego Zoo
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SSP Program Leader & Studbook
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Wildlife Conservation Society, Queens Zoo
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Education Advisor
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