An Assessment of the International Status of the Burrowing Owl (Athene cunicularia)

Rose Sanchez

ENVS 190 Senior Thesis

Dr. Foran

May 15, 2019

Burrowing owl at artificial nest entrance (Salton Sea, CA, USA) photographed by Jessie Barry

Table of Contents

Abstract .............................................................................................................................. 1

Introduction ....................................................................................................................... 2

Regional Status .................................................................................................................. 4

Western Canada and United States ................................................................................. 4

Mexico ............................................................................................................................ 9

Florida and the Caribbean ............................................................................................. 12

South America .............................................................................................................. 14

Discussion......................................................................................................................... 16

Tables ............................................................................................................................... 19

References ........................................................................................................................ 20

1

Abstract

The burrowing owl (Athene cunicularia) is a small, diurnal, and colonial owl species of

North and South America. Historically, burrowing owls have occupied short-grass prairies and

shrub-steppe habitats, but habitat degradation and human expansion have forced the owls into

human developments such as gold courses, airports, and schools. Across its range, their diet

consists of a variety of small mammals, insects, amphibians, reptiles, and small birds. Some

subspecies of burrowing owl migrate between Canada and the U.S. or Mexico, while other

subspecies occupy the same burrows year-round. Populations have experienced a sharp decline

in recent decades in response to conversion of grasslands for agriculture, reduced numbers of

prey species due spraying of insecticides and rodenticides, road collisions, and a number of other

factors that may not yet be identified. Management strategies between regions vary greatly, with

its status listed as Endangered in Canada and Minnesota, Threatened in Mexico, Colorado, and

Florida, and as a Species of Concern in seven U.S. states. Migratory paths and perils are only

partially understood, and information about the species in its wintering range in Mexico as well

as management strategies in South America are especially lacking. A concerted multi-national

effort to provide protections for the burrowing owl and fill in gaps in ecological knowledge will

be required to prevent the further decline of the species.

2

Introduction

Burrowing owls (Athene cunicularia) are a small bird (19-25 cm in length), mostly brown

with buffy white spotting and bright yellow eyes framed by a broad, buff eyebrow stripe, though

plumage can vary considerably among its fifteen subspecies (Poulin et al, 2011). They primarily

eat insects (e.g. grasshoppers, crickets, moths and beetles) and small mammals (e.g. mice, voles,

shrews), but they are opportunistic feeders and will also pursue larger prey like birds, snakes,

frogs, bats, and scorpions (Poulin et al, 2011). Unlike most owls, they are a diurnal species that

nest in small groups in underground burrows

abandoned by ground squirrels (tribe Marmotini);

although in previous centuries, some colonies were

recorded to contain several hundred pairs of owls

(Klute et al, 2003). These owls can be found in

grassland, savanna, desert, agricultural land, airports,

golf courses, and residential developments where there

are open, flat spaces with short grasses (Poulin et al,

2011).

Burrowing owls are distributed across North,

Central, and South America (Figure 1). Even though they are classified as Least Concern by the

IUCN, populations in North America have experienced a sharp decline in the last 50 years and

they are now endangered in Canada, threatened in Mexico, and listed by half the U.S. states they

occupy, ranging from having no legal status to Endangered (Table 1). The two subspecies of the

West Indies, A. C. amaura and A. C. guadeloupensis, are extinct. They are threatened across

their range by habitat destruction and degradation caused primarily by conversion of grassland to

Figure 1. Entire range of A. cunicularia.

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cropland and fragmentation of remaining grasslands, as well as the loss of burrows from ground

squirrel control measures (which have also been extirpated from 90% of their former range)

(Poulin et al, 2011). Other factors that have contributed to population decline include predation

by coyotes and feral cats, decreased prey abundance as a result of habitat changes, negative

effects of pesticides and herbicides, and collisions with vehicles (Environment Canada, 2012).

Current conservation efforts to bolster burrowing owl populations include captive

breeding and reintroduction programs, habitat protection, installation of artificial nest burrows,

pesticide restrictions, traffic signs, land stewardship agreements, and vegetation management

(Environment Canada 2012). The Burrowing Owl Conservation Network also identified several

key factors that must be emphasized in any restoration plan for these owls: open, flat space with

short grasses and no utility poles or high trees that could be used by aerial predators, an adequate

supply of arthropods, small mammals, birds, and reptiles for prey, conflict management with

other listed species such as the peregrine falcon, minimal human and pet-related disturbance, and

natural control of meso-predators like coyotes and feral cats by top predators like mountain lions

(Johnson et al, 2010).

The following will address the regional breeding biology, movement patterns, habitat use,

pesticide loads, genetics, behavior, and diet of burrowing owls, as well as threats to their

populations, and discuss how these factors have or have not contributed to the listing of the

species for conservation efforts by state or national agencies. Regional, state, and national

policies as well as nonprofit initiatives will also be compared and analyzed for their effect on

species listing. By analyzing the status of the burrowing owl across its entire range and

comparing conservation efforts, this paper will identify the regional and global needs of the

4

species, which may provide a current, useful resource to future burrowing owl researchers and

policy makers.

Regional Status

Western Canada and United States

Behavior and Threats.

The western burrowing owl (A. c. hypugaea) is distributed across Western North

America, primarily in sparsely vegetated grassland as well as in desert, grassland, and shrub-

steppe environments (Klute et al, 2003). Populations in this area have experienced a sharp

decline in the last 50 years and are still declining everywhere except in the core of their range in

the United States (e.g., Colorado and New Mexico). The wild population in British Columbia

(B.C.) was extirpated by the early 1980s,

as well as in Iowa and Minnesota. No

single factor has been identified as

causing the decline of the species; rather,

multiple, inter-related factors are

apparently responsible. Of the burrowing

owls that breed in Canada, two migration

patterns have been identified: one for

individuals east of the Rocky Mountains

through the Great Plains, and the second

for British Columbia along the west coast

of the U.S. (Figure 2) (Holroyd et al, Figure 2. Migratory paths tracked by VHF

transmitters (Holroyd et al, 2010).

5

2010); however, one banded female was reported to have crossed between these two migration

corridors from Arizona to Saskatchewan, traveling 1,860 km between two nesting attempts

within the same breeding season (Holroyd et al, 2011).

A study in the California Central Valley found that 80% of nocturnal foraging

observations occurred within 600 m of the nest (Gervais et al, 2003). In Canada, males hunt

within 1 km of the nest in ephemeral wetlands and uncultivated fields, and deer mice

(Peromyscus maniculatus) account for over 90% of their diet (Sissons et al, 2001). Western

burrowing owls migrate to Canadian breeding areas in April-May, and usually raise a single

clutch before migrating back southward in September-October (COSEWIC, 2006). In heavily-

cultivated regions of Saskatchewan, the owls preferred pastures but avoided croplands where

plants tend to be tall and dense, limiting access to prey (Sissons et al, 2001). Across Canada, they

have a very fragmented breeding distribution from southcentral Alberta through southern

Saskatchewan. A few reintroduced pairs breed in the Thompson-Nicola valley of B.C., and only

one pair has been confirmed in Manitoba since 1999 (COSEWIC, 2006). The current estimated

population is between 800 and 1,600 individuals, which represents a 90% population decline

from 1990 to 2000 (COSEWIC, 2006).

The California Burrowing Owl Consortium developed Survey Protocol and Mitigation

Guidelines to evaluate impacts from potential development projects such as airports and oil/gas

developments (CBOC, 2004); however, lack of awareness and inconsistent species management

policies across regions often leads to disastrous results. In 2013, the Center for Biological

Diversity filed a lawsuit against the city of San Diego after it discovered that herbicides had been

poured into owl burrows at the Brown Field Municipal Airport to intentionally kill the birds that

had nested under the helicopter pads, as well as to challenge a development proposal that would

6

destroy vernal pools and burrowing owl habitat in the surrounding area (Center for Biological

Diversity, 2013). In 2017, an agreement was reached to conduct a multi-year program with the

San Diego Zoo Institute for Conservation Research to reintroduce and rebuild the burrowing owl

population and to protect the adjacent wetland habitat (Center for Biological Diversity, 2017). If

the burrowing owl was state or federally listed, situations like these could be prevented

altogether through the CEQA/NEPA process.

Policy and Management.

Burrowing owls have no federal designation in the United States but were included as a

Bird of Conservation Concern at the national level by the US Fish and Wildlife Service

(USFWS) in 2002, and they are protected by the Migratory Bird Treaty Act of 1918. In 2003, the

Center for Biological Diversity, together with multiple Audubon societies and conservation

groups, petitioned the California Fish and Game Commission to list the western burrowing owl

as an endangered or threatened species, but it was rejected due to a lack of “sufficient scientific

information” on population trends, range, and immediacy of threats, among other factors

(Treanor, 2004), though the Center for Biological Diversity claims that the Commission’s

finding were based on an “inaccurate, inconsistent” report by the Department of Fish and

Wildlife that had suppressed the recommendations of its own biologists (Miller, 2019).

Within Canada, burrowing owls were designated as an Endangered species under the

Canadian Federal Species at Risk Act in 2003, and listed as Endangered by the provinces of

B.C., Alberta, Saskatchewan, and Manitoba, individually. When the species disappeared from

B.C. in the 1980’s, reintroduction efforts by Wildlife Preservation Canada and The Burrowing

Owl Conservation Society of B.C were made to capture and translocate adult owls from stable

populations in Washington and Oregon using a hard-release method, with no support given for

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the birds after release; however, this was not a success as no owls were found to have returned

after migration (Leupin & Low, 2001). Using an improved soft-release method that incorporated

supplemental feeding and installation of artificial nest burrows, 1,031 adult owls were released

between 2005-2015 that have successfully fledged over 1,880 offspring (Mitchell, 2008).

However, with a return rate of only 7.5%, the B.C. population is not self-sustaining and still

requires continued releases (Froese, 2016). However, high heterozygosity values and evidence of

gene flow suggest that population declines and patchy habitat have not led to inbreeding or

biologically meaningful genetic differentiation in western migrating populations (Korfanta,

2005).

From 1987-1996, over 200 artificial nest burrows were installed in suitable pastures in

southwestern Manitoba, which reduced predation of young and nesting adults (De Smet, 1997).

Several adult owls that returned to Manitoba selected an artificial burrow over the available

natural burrows, resulting in a nest re-occupancy of 44% and 13%, respectively (De Smet, 1997).

Also from 1987-1996, a campaign to increase the engagement of local interest groups and

landowners that included surveys, newspaper articles, mailing of brochure and insecticide alerts,

and local TV and radio appearances, located an additional 103 nests (De Smet, 1997). Wildlife

Preservation Canada also became involved in burrowing owl recovery in Saskatchewan in 1995,

using captive breeding and a soft-release method to establish new colonies within the province.

Mitchell et al (2011) confirmed that captive-reared burrowing owls show higher site-affinity,

survival, and reproductive performance when reintroduced using a soft-release.

8

A study on the post-fledging period of

burrowing owls in Saskatchewan found that

predators were the highest cause of mortality and

identified the first 14 days after fledging to be

the most at-risk (Todd et al, 2003). They also

found that juvenile survival had considerable

influence on population size in the next breeding

season. A long-term mark-recapture study found

that storms and above-average precipitation on

Canada wintering grounds was tied with lower

survival rates (Wellicome et al, 2014), which

could become a greater threat with predicted

climate change patterns.

Artificial burrow systems for burrowing

owls were first designed and used in the 1970s to

mitigate habitat loss and to help with

reintroduction programs (Figure 3). They were first built to measure 30 x 30 x 20 cm and were

buried to a depth of 15 cm, but later studies discovered that the owls prefer large chambers (such

as a 68-Liter bucket) that were buried at least 30 cm underground (Figure 4) in clusters of 2 or 3

(Johnson et al, 2010).

Figure 3. A wooden nest burrow design of

Collins and Landry (1977).

Figure 4. A durable and cost-effective

nest burrow design before being covered

by dirt and heavy rocks to ward off

digging by predators (Johnson et al,

2010).

9

Mexico

Behavior and Threats.

In Mexico, little is known about western burrowing owl populations as either residents or

migrants, but a review of museum specimens indicated that they are widespread in Mexico

during the winter (Figure 5) (Enríquez-Rocha, 1997). Studies on their biology and ecological

requirements are sparse (Rodríguez-Estrella, 1997), though the presence of the burrowing owl in

the Valley of Mexico has been

known since the 19th century

(Peterson & Navarro-Sigüenza,

2006). A Canadian team of

researchers flew 166.7 hours

searching the Gulf Coast lowlands

and central Mexico for signals

from 125 VHF transmitters that

were attached to burrowing owls

in Canada in 1997, 1998, and

2000, but only nine owls were located (Holroyd et al, 2010). In light of the evidence that the

breeding range of the western burrowing owl has contacted at its northern, western, and eastern

boundaries, it has been suggested that new breeding habitat may have been created through land-

use changes and agriculture in the arid areas of southwestern United States and northwestern

Mexico that have allowed the species to permanently occupy what used to only be used as

wintering grounds (Macias-Duarte, 2011). It’s possible that burrowing owls from northern

migratory populations have become annual residents in these areas that were formerly used only

Figure 5. Burrowing owl distribution in Mexico during

the breeding and non-breeding seasons as determined

from 279 museum specimens (Enriquez-Rocha 1997).

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by during winter, contributing to apparent population declines near the northern extent of the

species’ breeding range in Canada, but population increases in the southern half of the species’

range (Macias-Duarte, 2011). This hypothesis was somewhat supported by the analysis of DNA

microsatellite markers of 1,560 owls from 36 study locations in Canada, Mexico, and the United

States, that found that burrowing owl populations in both northwestern Mexico and Canada are

genetically different from other populations in its breeding range (Macias-Duarte, 2011).

There is also a subspecies of burrowing owl (A. C. rostrata) endemic only to Clarion

Island, 700 km from the coast of Baja California Sur (Figure 6). In contrast to mainland

burrowing owls that sometimes eat small mammals and reptiles, these birds are exclusively

insectivores (Hanna, 1926). They often make their burrows underneath small trees where red-

footed boobies (Sula sula) nest, and they have little fear of humans (Santaella & Sada,

1991)(Wanless et al, 2009). The introduction of feral pigs to Clarion Island in the 1980’s led to

the severe decline of many endemic bird species (Wanless et al, 2009). A 1989 study reported

that the Clarion burrowing owl was especially rare, and only 20 individuals were observed later

in 1991 (Santaella & Sada, 1991); however, when researchers returned in 2002 after the pigs had

been eradicated, burrowing owls had already

recovered and were the most conspicuous of all the

endemic species (Wanless et al, 2009). Using a

playback of territorial calls, the breeding population

was estimated at approximately 850 pairs or 42

pairs/km2 (Wanless et al, 2009). It is estimated that

the Clarion and western burrowing owls diverged

Figure 6. Location of Clarion Island

off the coast of Mexico.

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370,000 years ago, more than a million years after the Clarion Island emerged as a volcanic

island in the late Pliocene (Macias-Duarte, 2011).

Policy and Management.

In Mexico, A. C. hypugaea is federally listed as a Species of Special Concern, and A. C.

rostrata as Threatened (Herrera-Flores, 2010). In 1994, the Commission for Environmental

Cooperation (CEC) was established by Canada, Mexico, and the U.S. to facilitate cooperation on

environmental concerns related to the North American Free Trade Agreement (NAFTA) (and

later the United States–Mexico–Canada Agreement (USMCA)). One of the goals of the CEC is

to promote the conservation of the following migratory species: burrowing owl, leatherback sea

turtle (Dermochelys coriacea), humpback whale (Megaptera novaeangliae), pink-footed

shearwater (Puffinus creatopus), ferruginous hawk (Buteo regalis), black-tailed prairie dog

(Cynomys ludovicianus), vaquita (Phocoena sinus), and monarch butterfly (Danaus plexippus)

(CEC, 2005). These species were chosen based on a common understanding of shared threats to

each species, their distribution across the three counties, and probability of success.

The CEC Burrowing Owl Action Plan’s main objectives are to maintain/reestablish

health populations, conserve large blocks of native habitat, promote better management of the

habitat, determine the ultimate causes of population decline, and to facilitate trinational

communication and cooperation on conservation activities (CEC, 2005). A survey of biologists

in North America estimated that in 1992, there were between 20,000 and 200,000 burrowing

owls in the U.S., between 2,000 and 20,000 in Canada, and an unknown number in Mexico

(CEC, 2005). CEC has identified the need for a comprehensive, continental survey, as current

estimates of the entire sub-species are only derived from regional estimates (CEC, 2005). The

factors they recognize as causing burrowing owl population decline include the eradication of

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burrowing mammals, habitat loss and fragmentation due to agriculture, loss of prey due to

habitat degradation and insecticides, the gaps in data and understanding of the ecology of the

owls during non-breeding season, and the differences in the species’ listing and funding

availability across regions (CEC, 2005). CEC especially emphasizes that conservation in Mexico

is limited by funds and personnel for non-game species, and additional resources are needed to

assist Mexico in its conservation and training programs (CEC, 2005).

Florida and the Caribbean

Behavior and Threats.

The Florida burrowing owl’s (A. c. floridana) distribution is localized and patchy,

occurring primarily in peninsular Florida, with isolated pairs and small colonies found as far

west as Pensacola and as far south as the Dry Tortugas coral reef islands, as well as in the

Bahamas (Figure 7) (FFWCC, 2018). The typical breeding season is February to July, incubation

lasts about four weeks, and young first emerge from the burrow at two weeks after hatching

(FFWCC, 2018). Juveniles learn to fly by six

weeks of age but continue to use their parents’

burrows for 30-60 days after they start flying

(FFWCC, 2018). Unlike the Western burrowing

owl, Florida burrowing owls usually dig their

own burrows. These burrows can be 5-10 ft

long, but are excavated by the owls in as little

as 2 days (Millsap, 1996), but they are also

known to use burrows of gopher tortoises Figure 7. Range map of A. c. floridana

(FFWCC, 2018).

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(Gopherus polyphemus) or armadillos (Dasypus novemcinctus). During the breeding season, the

entrance to the nesting burrow may be decorated with adornments such as paper, shells, glass, or

pieces of plastic (Millsap, 1996). This subspecies is nonmigratory and they use their burrows

year-round, unless forced to leave due to flooding from seasonal rains (Mealey, 1997). These

owls prefer sandy, well-drained areas with vegetation of a height less than 5 inches, and may

abandon their burrows if visibility becomes impaired by overgrowth (FFWCC, 2018).

Historically, they used native dry prairies that covered central Florida, but as habitat

decreased from conversion to pasture, they have moved to inhabit human landscapes such as

schools, golf courses, and vacant lots (Millsap, 1996). Land clearing has resulted in the

expansion of habitat in all directions outside of the original central prairies (FFWCC, 2018);

however, most of this land is threatened by sea level rise within the next 50 years due to global

warming. The introduction of non-native wildlife is of concern, especially reptiles such as the

Argentine black and white tegu (Salvator merianae), Nile monitor (Varanus niloticus), green

iguana (Iguana iguana), and black spiny-tailed iguana (Ctenosaura similis), which will

opportunistically eat birds and have been found occupying burrowing owl burrows (FFWCC,

2018). Because they use their burrows year-round, their breeding and sheltering activities are

especially vulnerable to disturbance by harassment by humans or domestic animals, collapsing or

blocking of burrows, and habitat changes (FFWCC, 2018). A report by Florida Fish and Wildlife

estimated the owl’s probability of extinction was 0% in the next 100 years, but there was a 23%

probability of a 90% decline, and isolated populations (<5 individuals) had a >50% chance of

extirpation (FFWCC, 2011). Mean genetic diversity of burrowing owls is lower in the Florida

subspecies than in the west (0.539 and 0.341, respectively; P < 0.05) (Korfanta et al, 2005).

14

Policy and Management.

In Florida, the burrowing owl was listed as Threatened in 2017 and is protected by state

Rules 68A-16.001 and 68A-4.001, which prohibit the take, harm, or harassment of endangered or

threatened species and their nests or eggs. State listing was based on the criteria that all owls

were from one subpopulation, population size was estimated to be fewer than 10,000 adults, and

there is a projected decline in numbers (FFWCC, 2011). The actual population size is estimated

to be between 3,000 and 10,000, but researchers face difficulty accessing privately owned lands

in order to conduct studies to better assess the current status of the owls. Current management is

limited to the above take laws, and there is a lack of management strategies for burrowing owls

in rural areas (FFWCC, 2011) or adequate habitat protection in urban environments (Millsap,

1996).

Unlike in other regions, simple starter burrows, such a partially excavated tunnel, are

often enough to attract the attention of burrowing owls in this area, who then finish digging out

the burrow on their own (FFWCC, 2018). These starter burrows are always placed on sandy soils

that are easy to dig out, in open, well-drained areas away from visual obstructions and at least 90

m from a forested edge (FFWCC, 2018).

South America

Behavior and Threats.

Burrowing owls are widely distributed throughout South America, through southern

Chile and Argentina. Subspecies on the continent include: A. c. cunicularia in lowlands of south

Bolivia, south Brazil, and the grasslands of Argentina, A. c. grallaria of central and eastern

Brazil, A. c. nanodes of southwestern Peru, A. c. brachyptera of Isla Margarita, A. c. tolimae of

15

west Colombia, A. c. juninensis of northwest Argentina and the altiplano region of the Peru-

Ecuador border, A. c. minor of south Guayana, A. c. pichinchae of west Ecuador, and A. c.

boliviana of the Bolivian altiplano.

Burrowing owls in South America are associated with small, isolated patches, possibly

because patch size and habitat quality are inversely related, and large open patches may increase

detection by predators (Villarreal, 2005). Burrowing owls in western South America primarily

eat insects, arachnids, mammals (especially Phyllotis darwini), and the terrestrial toad Rhinella

arunco, and rarely prey upon birds or reptiles (Jaksic et al, 1997). In response to the El Nino

Southern Oscillation of 1991-92, burrowing owls strongly responded to the resulting increases in

mammalian prey levels, indicated that although insects numerically dominate their diet,

mammals are their staple prey (Jaksic et al, 1997). In Brazil, an analysis of 1,044 pellets

supported that invertebrates are numerically the main prey, mostly represented by termites,

orthoptera and beetles, but small rodents such as Calomys tener formed the bulk of the biomass

(Motta-Junior & Bueno, 2004). This was again found to be true in Chile, indicating that

burrowing owls should be classified tropically as carnivorous predators (Silva, 1995). In general,

termites were more consumed in the dry season (April to September), whereas beetles were more

preyed on in the rainy season (October to March) (Motta-Junior & Bueno, 2004). They are

sometimes seen forming a “predator guild” with culpeo foxes (Lycalopex culpaeus), austral

pygmy owls (Glaucidium nana), and barn owls (Tyto alba), possibly for their high and shared

consumption of P. darwini and A. bennetti (Jaksic et al, 1997). The southernmost subspecies, A.

c. cunicularia, has a larger body size than the North American and Caribbean subspecies, which

suggests geographical variation in body size of this species (Baladron et al, 2015).

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Policy and Management.

The Article 225 of the Brazil Constitution states the right to an ecologically balanced

environment to all people, and the Government shall "preserve and restore the essential

ecological processes and provide for the ecological treatment of species and ecosystems."

Burrowing owls may benefit from fire management practices, as they have been found to prefer

the short vegetation of firebreaks (bands of vegetation marked by low biomass in attempt to stop

fire spreading) created in the grasslands of Cerrado, Brazil rather than unmanaged grasslands

(Tubelis & Delitti, 2010), though, within the same region, they were the most commonly found

dead in a study of road-killed birds along a section of the highway (Bencke & Bencke, 1999).

Specific programs and policies for the protection and management of the burrowing owl

in the countries of South America are not readily available in English. This subject would be

benefitted from a future analysis of individual country’s laws and regulations by a Spanish-

speaking student.

Discussion

Future studies should focus on identifying the yearly immigration-emigration patterns of

migratory burrowing owl populations to better understand why populations are declining

regionally. Recommended conservation practices are consistent throughout the burrowing owl’s

range. Avoiding the use of pesticides, rodenticides, insecticides, and herbicides immediately

around the burrow entrance and in foraging habitat during nesting season will limit the chance of

the owls and chicks injesting poisons. In urban areas, suggestions include reducing speed limits

near burrow colonies, not building tall structures that could reduce visibility from the burrow,

and using light equipment (e.g. weed trimmer) to trim vegetation around the burrows. In rural

17

areas, a selective cattle-grazing regime can be used to keep

vegetation at a height that is beneficial for the owls, but too

many cattle may also degrade soil quality and destroy burrows

so a metal frame to protect the burrows is recommended

(FFWCC, 2018). Placement of artificial burrows with t-shaped

wooden perches at the entrance have had success across the

owl’s entire range. Biologists and other professionals should

take the burrowing owl’s propensity for being a victim of

automobile collisions into account when assessing the

environmental impacts of new roads, and a monitoring program

should be implemented to reduce the probability of road deaths.

The construction of roads through parks and reserves that the

owls occupy should be avoided at all costs. Installing signs near burrows (figure 8), and

preventing public access to occupied areas during breeding season would encourage the public to

respect the needs of the burrowing owls and prevent collapse or abandonment of the nest.

Burrowing owls in Mexico, Central America, South America, and the West Indies are

vastly underrepresented in the literature for the species. Considering the amount of effort put into

conservation for the species in Canada, data on the burrowing owl’s wintering range in Mexico is

incredibly limited. Additional effort is needed to translate and analyze studies that are available

from the region, and to encourage conservation organizations like the California Burrowing Owl

Consortium and Commission for Environmental Cooperation as well as state and federal

environmental agencies to fund studies in Mexico. The cause of the low rate of banded birds that

return to Canada is only hypothesized, and it would be incredibly useful to management

Figure 8. Sign used to

mark burrows on Naval

Air Station North Island,

San Diego, CA (CBOC,

2004)

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strategies if it was known whether the birds were perishing on their journeys to/from their

wintering grounds, or simply colonizing new year-round habitats. As a migratory bird, the

western burrowing owl is dependent on habitats that cross national borders. Inconsistent listings

and management policies threaten the species and threaten the efficacy of conservation efforts in

regions that have already acknowledged the imperiled status of this unique species.

The charismatic and sometimes comical burrowing owl in an easily recognized icon of

the grasslands of North and South America. Their populations have been critically threatened by

a myriad of factors related to human activity, and creating a long-term conservation plan will

require the synthesis of a wide variety of sources. Recovery is possible, but it will be dependent

on a high level of effort and international cooperation among governments, NGOs, industry,

stakeholders, landowners, and the public.

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Tables

Table 1. Legal status and natural heritage status of the Burrowing Owl (Athene cunicularia)

in the United States, Canada, and Mexico1.

Area Legal Status Natural Heritage Status

United States None Apparently Secure

Arizona None Vulnerable

California Species of Concern Imperiled

Colorado Threatened Apparently Secure

Florida Threatened Vulnerable

Idaho None Vulnerable

Iowa Accidental breeder Unranked

Kansas None Vulnerable

Minnesota Endangered Critically Imperiled

Montana Species of Concern Vulnerable

Nebraska None Vulnerable

Nevada None Vulnerable

New Mexico None Apparently Secure

North Dakota None Unranked

Oklahoma Species of Concern Vulnerable

Oregon Species of Concern Imperiled

South Dakota None Vulnerable

Texas None Vulnerable

Utah Species of Concern Vulnerable

Washington Species of Concern Vulnerable

Wyoming Species of Concern Vulnerable

Canada Endangered Vulnerable

Alberta Endangered Vulnerable

British Columbia Endangered Critically Imperiled

Manitoba Endangered Critically Imperiled

Saskatchewan Endangered Imperiled

Mexico Threatened Unranked

1 Adapted from the USFWS Status Assessment and Conservation Plan for the western burrowing owl (Klute et. al., 2003).

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References

Baladrón, A. V., Cavalli, M., Isacch, J. P., & Madrid, E. (2015). Body size and sexual

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