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f ever a single keystone rowing perched quietly on a fencepost, were to be identified with the or peering quizzically out of a I ecosystems of North America, the hole. Whether standing solemnly beside a black-tailed prairie dog (Cynomys ludovi- prairie dog hole, or perched on a low fence- cianus) would probably most easily qualify. post, a miniature owl standing erect and in are those that plain view during the middle of the day tend to hold an ecosystem together, and somehow seems to be such an unlikely ap- whose presence or absence has the greatest parition that it requires prolonged and ex- effect on the well-being of the other tensive study. There is something in the an- species. In various ways it can be argued imal’s intense yellowish-green eyes that that predators such as the black-footed fer- demands to be watched with equal inten- ret (Mustela nigripes), swift fox (Vulpes sity, and the Burrowing Owl’s velox), (Canis latrans), Ferrugi- comical, not-quite-erect stance nous Hawk, Golden Eagle, and prairie might remind one of a rattlesnake (Crotalus v. viridis) all spindly-legged, feather-clad largely or partly depended histori- leprechaun still trying to cally on the black-tailed prairie recover from last night’s dog as prey. The ecological ef- hangover. The seemingly fects of prairie dogs on sur- curious if not actually rounding vegetation are friendly manner of the also exploited by Mountain Burrowing Owl when ap- Plover, Horned Lark, vari- proached by humans is ous ground squirrels probably the reason that in (Spermophilus spp.), and some parts of the American West grasshopper mice (Ony- the species is known as the chomys spp.). The “howdy” owl. prairie dogs’ aban- The usual rules of owl decorum doned burrows are do not apply to Burrowing . used by horned lizards First, they are not as highly (Phrynosoma spp.), spade- nocturnal as most other foot toads (Spea spp.), tiger sala- owls, but instead are ac- Paul A. Johnsgard manders (Ambystoma tigrinum), and a vari- tive mainly during broad School of Biological Sciences ety of . Perhaps no other daylight. In fact, their retinas lack the re- University of Nebraska North American animal can claim so many flective surface that increases nocturnal vi- uninvited guests as the prairie dog, and sual sensitivity and produces the “eye Lincoln, Nebraska perhaps the most charismatic of these is the shine” typical of most owls. Secondly, un- 68588-0118 Burrowing Owl. like the larger owls of the , Bur- [email protected] Few birds will bring birders screeching rowing Owls are surprisingly insectivo- their cars to a halt faster than will a Bur- rous, at least during the summer months

40 BIRDING • JANUARY/FEBRUARY 2006 “They can burn grasses with their stare. Yellow eyes magnifying light.”So writes Terry Tempest Williams of the Burrowing Owl, in her book Refuge. Kansas; October 2001. © Bob Gress. when large, slow-moving insects, such as dung bee- tles ( spp.) and ground beetles (Cara- bidae spp.), are abundant around dog towns and are easily captured. Thirdly, Burrowing Owls seem to lack the acute binaural hearing and precise sound- source localization abilities that owls as a group are primarily noted for, and instead appear to rely on their keen daytime vision for prey-finding. In corre- lation, their faces have only poorly developed facial disk feathers surrounding their ears, which help fun- nel extremely faint sounds into the ear canals of the most highly nocturnal owls. When a Burrowing Owl is confronted by an ap- proaching human, it is more likely to stay put than to fly away immediately. Often, after a few slight hori- zontal or vertical head movements by the , as if trying to shake its head clear of a foggy memory, but which are probably designed to get a better distance- estimating fix on the new intruder into its personal space, the owl will probably duck back into its hole. Or, if perched on a post, it may take silent flight over the prairie dog town and land near its burrow en- trance. When cornered in its burrow, a Burrowing Owl will produce a sound that mimics a rattlesnake’s rattle, and at such times may also spread and tilt its wings vertically, apparently to make itself appear larger and more dangerous. The male’s courtship call is usually soft and owl-like, but adults of both sexes also utter a rapid chatter when alarmed or while de- fending the nest. Although a Burrowing Owl is perfectly content to take over a prairie dog burrow without making major structural changes or other renovations, it is likely to gather fragments of dried bison or cattle dung, break them into small pieces, and line the entrance area in Unlike most owl species, the charismatic Burrow- ing Owl is diurnal. With a little bit of patience, the front of its burrow with these bits of debris. Such birder can observe various aspects of this bird’s markings help one to recognize an active Burrowing elaborate behavior and complex ecology. Arapahoe Owl burrow, as do the dried owl pellets that are usu- County, Colorado; July 1990. © D. Robert Franz. ally rich in chitinous insect fragments such as the

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undigested exoskeletal remnants of grasshoppers and scarab showed a population increase was following a peak in vole and carabid beetles. populations. The biological function of the scattered ungulate droppings Besides using prairie dog burrows, Burrowing Owls have is uncertain, but they may help mask the odors of an active also occasionally adapted to living in burrows made by ground owl burrow, for Burrowing Owls are highly vulnerable to squirrels, marmots and woodchucks (Marmota spp.), badgers, badgers (Taxidea taxus). In a 1989 study, Gregory Green and foxes, , skunks, nine-banded armadillos (Dasypus Robert Anthony found that, next to desertion, badgers were novemcinctus), kangaroo rats (Dipodomys spp.), and tortoises. the most significant source of Burrowing Owl nesting mortal- They may also dig their own burrows in the absence of avail- ity, but that nests lined with livestock dung were significantly able housing already provided by burrowing . They less susceptible to than were unlined nests. Addi- have even been known to use natural rock cavities and to ac- tionally, it has been suggested that the presence of dung may cept human-made artificial burrows where natural excava- help attract dung beetles to the nest, where they can be easily tions are not possible. captured by the owls. On the , it is primarily the black-tailed prairie The Burrowing Owl is the only strongly migratory owl of dog that offers the owls housing. It has been estimated that 95 the northern plains, presumably because its insect foods be- percent of all the Burrowing Owls nesting on the Comanche, come progressively unavailable in fall. Then it turns increas- Cimarron, Rita Blanca, and Kiowa National Grasslands, all lo- ingly to relatively small such as pocket mice (Het- cated in the southern Great Plains, were directly associated eromyidae spp.) for food. Although small mammals and birds with prairie dog towns, according to an unpublished study by make up a low percentage of the summer diet as measured by Shawn Conrad, Jennifer Dose, and Dan Svingen. Only three of their sheer number (about 5–20%), the much larger body 114 prairie dog towns supporting Burrowing Owls lacked ac- mass of mammals relative to insects tends to make mammals tive prairie dog burrows, indicating the importance of “dog” comprise the predominant portion (about 80–95%) of the bio- activity in making good owl breeding sites. The three inactive mass of all foods taken. Frogs, toads, lizards, snakes, and even towns supporting Burrowing Owls had apparently been inac- turtles have also been reported as Burrowing Owl fare, as well tive for only one year. Likewise, among 543 Burrowing Owl as birds at least as large as Horned Larks (Haug et al. 1993). nests found in the Panhandle, two-thirds were lo- There is also some hunting activity at night, especially during cated within black-tailed prairie dog colonies (Butts and Lewis bright moonlit nights, 1982). Besides being able to exploit inactive dog and at these times small burrows, the owls favor the combination of low nocturnal rodents such shrub coverage, short vegetation, and high per- as voles and pocket mice centage of bare ground that is typically present in would be the most likely prairie dog colonies. When the ground-level vi- targets. Ray Poulin sion is variously obstructed, the birds find suit- (2003) determined that able nearby observation posts to use, such as in Saskatchewan the pri- fenceposts or boulders. mary owl foods are deer Within prairie dog towns, Burrowing Owls fa- mice (Peromyscus spp.) vor larger and active colonies; typically, a town and meadow voles (Mi- that has been abandoned by prairie dogs will also crotus spp.), and the be abandoned by Burrowing Owls within three only year that the owls years, perhaps largely as a result of encroachment Boulder, Colorado; October 2004. © Bill Schmoker.

FFortort NiobrNiobraraara NNationalational Wildlife The black-tailed prairie dog (inset) is a so-called “keystone species”, meaning that Refuge,Refuge, NNebraska;ebraska; June 2004. numerous other species in the environment depend upon its presence. The Burrowing © Paul A. Johnsgard. Owl, which nests and roosts in prairie dog burrows, is one such dependent species.

42 BIRDING • JANUARY/FEBRUARY 2006 of dense vegetation, but also because of the gradual dete- rioration of the burrows themselves. Within active towns, the owls often choose nests near the periphery of the colony, where there may be a greater abundance of in- sects, more available nearby perches, and a proximity to foraging areas. Burrowing Owls may also favor sites offer- ing several “satellite” burrows, used by both adults and young, perhaps to avoid the buildup of nest parasites and loss of an entire family to predators. As many as five such satellite burrows may be used by a single owl family, which may contain a half dozen or more owlets of vary- ing ages and sizes. For the Great Plains as a whole, Burrowing Owl occu- pancy rates of active prairie dog colonies are substantial- ly lower in the northern Great Plains national grasslands than in those of the southern Great Plains (Sidle et al. 2001). Regardless of geographic location, Burrowing Although Burrowing Owl families may be found anywhere in a prairie dog colony, Owls were found in one study to use active dog towns at the preferred location for nest-placement seems to be along the outskirts of the a rate 6.3 times greater than at inactive ones, evidencing “town”. Keith County, Nebraska; June 1980. © Paul A. Johnsgard. the need for active prairie dog colonies to maintain breed- ing habitat for Burrowing Owls. The presence of live prairie . In Wyoming, Thunder Basin is dogs not only means that there will be a ready supply of new- a potential site for Burrowing Owls and other shortgrass fau- ly abandoned but structurally intact burrows available to the na, although prairie dog poisoning is being carried out there, owls, but also that the owls may exploit the efficient warning too. In Kansas, Prairie Dog Lake State Park and Smoky Valley system of the prairie dogs. There is no proof that prairie dogs Ranch have Burrowing Owls, and they are also relatively com- directly benefit from the presence of Burrowing Owls, and the mon on Cimarron National Grassland. However, many Kansas ever-alert rodents sometimes utter alarm notes when the owls counties have mandatory prairie dog eradication programs, fly overhead, suggesting that prairie dogs are at least some- and Burrowing Owls are now essentially limited to the three what wary of the owls. westernmost tiers of counties. There are progressively more Burrowing Owls to be found as Where to Find Burrowing Owls one moves into the southwestern plains. In eastern Colorado, Birders who want to see Burrowing Owls firsthand in the Comanche, Cimarron, and Pawnee National Grasslands all Great Plains region have many choices. In Canada, support Burrowing Owls, as does the Rocky Mountain Arsenal Saskatchewan Landing Provincial Park and Grasslands National Park offer possibilities. In Montana, there are Bowdoin, Charles M. Russell, and Medicine Lake National Wildlife Refuges, as well as the National Bi- son Range and the difficult-to-access UL Bend . In North Dakota the Little Missouri National Grass- land and Theodore Roosevelt National Park are good choices for owl-watchers. In South Dakota, Badlands and Wind Cave National Parks, Buffalo Gap and Fort Pierre National Grasslands, and Custer State Park are all ex- cellent choices. Nebraska’s Fort Niobrara National Wildlife Refuge usually has Bur- rowing Owls visible near the refuge head- quarters, but to placate ranchers with graz- ing interests, prairie dogs are still being Burrowing Owls are tolerant of human presence, and small colonies are often found near golf courses, housing poisoned on most state and federal lands in developments, and agricultural fields. But the species is threatened by outright habitat destruction, along with Nebraska, including the Oglala National continuing persecution of black-tailed prairie dogs. Arapahoe County, Colorado; July 1989. © D. Robert Franz.

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National Wildlife Refuge near Denver. In Oklahoma, population in excess of State Park and Optima, Salt Plains, Washita, 10,000 pairs in the 1990s, and Wichita Mountains National Wildlife Refuges all and states with popula- have breeding Burrowing Owls. The species is fairly tion estimates of 1,000– common at Bosque del Apache, Bitter Lake, and Las Ve- 10,000 pairs were Col- gas National Wildlife Refuges in eastern . orado, New Mexico, Wyo- Burrowing Owls are also common in Texas at Buffalo ming, and Nevada. States Lake and Muleshoe National Wildlife Refuges, and at with 100–1,000 estimat- Rita Blanca National Grassland. ed pairs included Kansas, The Florida population is of a different and sedentary Montana, Nebraska, North (floridana; the widespread western sub- Dakota, Oklahoma, and species is hypugaea), and other resident races also occur South Dakota. Burrowing in the West Indies. One population estimate for Florida Owls have been essential- is 3,000–10,000 adults (Haug et al. 1993). In Florida, ly extirpated from Iowa. the owls typically dig their own burrows, although the During the summer months, the Burrowing Owl’s diet In western Nebraska one (Gopherus polyphemus) is a potential consists mainly of arthropods. Arapahoe County, population study (Des- source of ready-made burrows. Population data for Colorado; July 1990. © D. Robert Franz. mond and Eskridge 2000) Florida do not show statistically significant trends, but the indicated that a 58% population decline of Burrowing Owls Florida population has fairly high adult annual survival and occurred between 1990 and 1996, during a period of intensive breeding success rates, with a few known cases of two broods prairie dog poisoning and their associated rapid population being produced in a single year. declines. Although there have also been some apparent re- The species is now classified as Nationally Endangered in gional increases in the southwestern grasslands and the Canada. T. I. Wellicome and E. A. Haug estimated (1995 re- interior northwestern grasslands, the greatest declines have port to Committee on the Status of Endangered Wildlife in occurred in the northern Great Plains. Sadly, the familiar Canada) the mid-1990s population for the Canadian prairie “howdy” owl of the plains is in increasing danger of having to provinces at between 1,010 and 1,685 pairs, with 5–10 addi- say “adios” to much of western North America. tional pairs in British Columbia as a result of reintroduction efforts there. Burrowing Owls are classified as Nationally Literature Cited Threatened in Mexico, although their numerical status there is Butts, K.O., and J.C. Lewis. 1982. The importance of prairie dog towns to Burrowing unknown. The species also occurs in Central American grass- Owls in Oklahoma. Proceedings of the Oklahoma Academy of Science 62:46–52. lands, in South America from Venezuela to Tierra del Fuego, Conrad, S.T., J.L. Dose, and D.N. Svingen. Burrowing Owl Association with Prairie Dog and locally in the West Indies. Towns in the Southern Great Plains, unpublished manuscript. U.S. Forest Service, Returning to western North America, the Burrowing Owl is Springfield. state-endangered in Minnesota, is threatened in Colorado, and Desmond, M.J., and K.M. Eskridge. 2000. Correlations between Burrowing Owl and is considered to be a species of concern in seven additional black-tailed prairie dog declines: A 7-year analysis. Journal of Wildlife Management states. A range-wide survey of Burrowing 64:1067–1075. Owl populations by James and Espie Green, G.A., and R.G. Anthony. 1989. Nesting success and habitat relationships of Bur- (1997) suggested that as of the early rowing Owls in the Columbia Basin, Oregon. Condor 91:347–354. 1990s there may have then been Haug, E.A, B.A. Millsap, and M.S. Martell. 1993. Burrowing Owl ( cunicularia), in: 20,000–200,000 breeding pairs in A. Poole and F. Gill, eds. The Birds of North America, no. 61. Academy of Natural the United States. In the Great Sciences, Philadelphia, and American Ornithologists’ Union, Washington. Plains, Texas had an estimated James, P.C., and R.H.M. Espie. 1997. Current status of the Burrowing Owl in North America: An agency survey, pp. 3–5 in: J.L. Lincer and K. Steenhof, eds. The Bur- Although the Burrowing Owl remains wide- rowing Owl: Its Biology and Management, Including the Proceedings of the First spread in North America, with populations scat- Burrowing Owl Symposium, research report no. 9. Raptor Research Foundation, tered throughout the West and an Boise. isolated population in Florida, the species is in overall decline. The Poulin, R.G. 2003. Relationships between Burrowing Owls (Athene cunicularia), Small greatest declines have occurred Mammals, and Agriculture, dissertation. University of Saskatchewan, Regina. in the northern Great Plains. Sidle, J.G., M. Ball, T. Byer, J.J. Chynoweth, G. Foli, R. Hodorff, G. Moravek, R. Peterson, Arapahoe County, Colorado; July and D.N. Svingen. 2001. Occurrence of Burrowing Owls in black-tailed 1990. © D. Robert Franz. prairie dog colonies on Great Plains national grasslands. Journal of Raptor Research 35:316–321.

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