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Home , Athene (bird), Burrowing owl

An Assessment of the International Status of the Burrowing ( 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 ...... 12

South America ...... 14

Discussion...... 16

Tables ...... 19

References ...... 20

Abstract

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

North and South America. Historically, burrowing have occupied short-grass 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 , insects, amphibians, reptiles, and small . Some 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 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.

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Introduction

Burrowing owls (Athene cunicularia) are a small (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 (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 , savanna, , agricultural land, airports, golf courses, and residential developments where there are open, flat spaces with short grasses (Poulin et al,

2011). Figure 1. Entire range of A. cunicularia. 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

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

3 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 , 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).

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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

5 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 , 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 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

6 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 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.

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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 Figure 3. A wooden nest burrow design of influence on population size in the next breeding Collins and Landry (1977). 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 Figure 4. A durable and cost-effective nest burrow design before being covered owls were first designed and used in the 1970s to by dirt and heavy rocks to ward off digging by predators (Johnson et al, mitigate habitat loss and to help with 2010). 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).

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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 Figure 5. Burrowing owl distribution in Mexico during were attached to burrowing owls the breeding and non-breeding seasons as determined from 279 museum specimens (Enriquez-Rocha 1997). 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

9 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 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), (Buteo regalis), black-tailed 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

11 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), (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 , collapsing or blocking of burrows, and habitat changes (FFWCC, 2018). A report by Florida Fish and Wildlife estimated the owl’s probability of 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).

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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

14 west , 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 are numerically the main prey, mostly represented by , and beetles, but small 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

16 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 Figure 8. Sign used to environmental impacts of new roads, and a monitoring program mark burrows on Naval Air Station North Island, should be implemented to reduce the probability of road deaths. San Diego, CA (CBOC, 2004) 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

17 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 dimorphism in the southernmost subspecies of the Burrowing Owl (Athene cunicularia cunicularia). Journal of Raptor Research, 49(4), 479-486. Bencke, G. A., & Bencke, C. S. C. (1999). The potential importance of road deaths as a cause of mortality for large forest owls in southern Brazil. Cotinga, 11, 79-80. California Burrowing Owl Consortium (CBOC). (2004). California burrowing owl consortium survey protocol. In J. L. Lincer & K. Steenhof (Eds.), Raptor Research Report (Vol. 9, pp. 171-177). Center for Biological Diversity. (2013, November 21). Lawsuit Filed to Save San Diego's Vanishing Burrowing Owls and Wetlands: Groups Urge City to Stop Poisoning, Destruction of Burrowing Owls at Airport [Press release]. Center for Biological Diversity. (2017, January 23). Agreement Protects San Diego's Vanishing Burrowing Owls, Increases Solar Energy [Press release]. Commission for Environmental Cooperation (CEC). (2005). Western Burrowing Owl: North American Conservation Action Plan (pp. 1-45, Rep.). Collins, C. T. & R. E. Landry. (1977). Artificial nest burrows for Burrowing Owls. North American Bird Bander, 2(4), 151-154. Committee on the Status of Endangered Wildlife in Canada (COSEWIC). (2006). COSEWIC assessment and update status report on the Burrowing Owl Athene cunicularia in Canada. Ottawa: Committee on the Status of Endangered Wildlife. De Smet, K. D. (1997). Burrowing Owl (Speotyto cunicularia) monitoring and management activities in Manitoba, 1987-1996. In J. R. Duncan, D. H. Johnson, Nicholls, & H. Thomas, Biology and conservation of owls of the Northern Hemisphere: 2nd international symposium. (Vol. 190, pp. 123-130, Rep. No. NC-190). St. Paul, MN: US Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. Enriquez-Rocha, P. L. (1997). Seasonal records of the burrowing owl in Mexico. Journal of Raptor Research Report, 9, 49-51. Environment Canada. 2012. Recovery strategy for the Burrowing Owl (Athene cunicularia) in Canada. Ottawa, Canada.

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Florida Fish and Wildlife Conservation Commission (FFWCC). (2011). Florida Burrowing Owl Biological Status Review Report (pp. 1-16, Rep.). Tallahassee, FL. Florida Fish and Wildlife Conservation Commission (FFWCC). (2018). Florida Burrowing Owl Athene cunicularia floridana (Species Conservation Measures and Permitting Guidelines, pp. 1-30, Rep.). Froese, A. (2016). Breeding Ecology of Wild and Captive-released Burrowing Owls (Athene cunicularia) in Southwestern Manitoba (Master's thesis, University of Winnipeg) (pp. 1- 101). Gervais, J. A., Rosenberg, D. K., & Anthony, R. G. (2003). Space use and pesticide exposure risk of male burrowing owls in an agricultural landscape. The Journal of wildlife management, 155-164. Hanna, G. D. (1926). Expedition to the , Mexico, in 1925. Proceedings of the California Academy of Sciences, 15, 1-113 Herrera-Flores, S. D. (2010). Protección ambiental-Especies nativas de México de flora y fauna silvestres-Categorías de riesgo y especificaciones para su inclusión, exclusión o cambio- Lista de especies en riesgo (pp. 1-232) (México, Secretaría del Medio Ambiente y Recursos Naturales). Holroyd, G. L., Trefry, H. E., & Duxbury, J. M. (2010). Winter destinations and habitats of Canadian Burrowing Owls. Journal of Raptor Research, 44(4), 294-300. Holroyd, G. L., Conway, C. J., & Trefry, H. E. (2011). Breeding dispersal of a Burrowing Owl from Arizona to Saskatchewan. The Wilson Journal of Ornithology, 123(2), 378-381. Jaksic, F. M., Silva, S. I., Meserve, P. L., Gutiérrez, J. R., & Gutierrez, J. R. (1997). A Long- Term Study of Predator Responses to an El Niño (ENSO) Disturbance in Western South America. Oikos,78(2), 341-354. Johnson, D. H., Gillis, D. C., Gregg, M. A., & Rebholz, J. L. (2010). Users guide to installation of artificial burrows for Burrowing Owls (pp. 1-34, Rep.). Selah, WA: Tree Top. Klute, D. S., L. W. Ayers, M. T. Green, W. H. Howe, S. L. Jones, J. A. Shaffer, S. R. Sheffield, & Zimmerman T. S. (2003). Status Assessment and Conservation Plan for the Western Burrowing Owl in the United States (Rep. No. BTP-R6001-2003). Washington, D.C.: U.S. Department of Interior, Fish and Wildlife Service.

21

Korfanta, N. M., McDonald, D. B., & Glenn, T. C. (2005). Burrowing Owl (Athene cunicularia) population genetics: a comparison of North American forms and migratory habits. The Auk, 122(2), 464-478. Leupin, E. E., & Low, D. J. (2001). Burrowing Owl reintroduction efforts in the Thompson- Nicola region of British Columbia. Journal of Raptor Research, 35(4), 392-398. Macias-Duarte, A. (2011). Change in Migratory Behavior as a Possible Explanation for Burrowing Owl Population Declines in Northern Latitudes (Unpublished doctoral dissertation). University of Arizona. Mealey, B. (1997). Reproductive ecology of the Burrowing Owls, Speotyto cunicularia floridana. Dade and Broward counties, Florida. Journal of Raptor Research Report, 9, 74-79. Miller, J. (2019). Saving the Western Burrowing Owl. Retrieved from https://www.biologicaldiversity.org/species/birds/western_burrowing_owl/ Millsap, B. A. (1996). Florida burrowing owl. In J. A. Rodger, H. W. Kale II, & H. T. Smith (Eds.), Birds (Vol. 5, Rare and endangered biota of Florida, pp. 579-587). Gainesville: University Presses of Florida. Mitchell, A. M. (2008). The effects of release techniques on the reproductive performance and post-fledging juvenile survival of captive-bred Western Burrowing Owls (Athene cunicularia hypugaea) in the Nicola Valley, British Columbia (Doctoral dissertation, University of British Columbia). Mitchell, A. M., Wellicome, T. I., Brodie, D., & Cheng, K. M. (2011). Captive-reared burrowing owls show higher site-affinity, survival, and reproductive performance when reintroduced using a soft-release. Biological Conservation, 144(5), 1382-1391. Motta-Junior, J. C., & Bueno, A. A. (2004). Trophic ecology of the Burrowing Owl in southeast Brazil. In Raptors worldwide: proceedings of the VI world conference on birds of prey and owls (R. Chancellor and B.-U. Meyburg, Eds.). World Working Group on Birds of Prey and Owls, MME BirdLife Hungary, Budapest (pp. 763-775). Peterson, A. T., & Navarro, A. G. (2006). Hundred-year changes in the avifauna of the Valley of Mexico, Distrito Federal, Mexico. Huitzil, Revista Mexicana de Ornitología, 7(1), 4-14.

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Poulin, R. G., Haug, E. A., Millsap, B. A., & Martell, M. S. (2011). Burrowing Owl (Athene cunicularia) (A. F. Poole, Ed.). In The Birds of North America (2nd ed.). Ithaca, NY: Cornell Lab of Ornithology. Rodriguez-Estrella, R. (1997). Nesting sites and feeding habits of the Burrowing Owl in the biosphere reserve of Mapimi, Mexico. Journal of Raptor Research Report, 9, 99-106. Santaella, L., & Sada, A. M. (1991). The avifauna of the Revillagigedo Islands, Mexico: Additional data and observations. The Wilson Bulletin, 103(4) 668-675. Silva, S. I. (1995). Numerical and Functional Response Of Burrowing Owls To Long-Term Fluctuations In Chile. Journal of Raptor Research, 29(4), 250-255. Sissons, R. A., Scalise, K. L., & Wellicome, T. I. (2001). Nocturnal foraging and habitat use by male Burrowing Owls in a heavily-cultivated region of southern Saskatchewan. Journal of Raptor Research, 35(4), 304-309. Todd, L., Poulin, R., Wellicome, T. & Brigham, R. (2003). Post-Fledging Survival of Burrowing Owls in Saskatchewan, Journal of Wildlife Management, 67(3), 512-519. Treanor, R. R. (2004). Finding relating to the petition to list the western burrowing owl as endangered or threatened (pp. 1-11, Rep.). Sacramento, CA: California Fish and Game Commission. Tubelis, D. P., & Delitti, W. B. C. (2010). Fire management and the nesting of Athene cunicularia (Aves, Strigidae) in grasslands in central Cerrado, Brazil. Biota Neotropica, 10(2), 93-101. Villarreal, D., Machicote, M., Branch, L. C., Martinez, J. J., & Gopar, A. (2005). Habitat patch size and local distribution of burrowing owls (Athene cunicularia) in Argentina. Ornitol Neotrop, 16(4), 529-537. Wanless, R. M., Aguirre-Muñoz, A., Angel, A., Jacobsen, J. K., Keitt, B. S., & McCann, J. (2009). Birds of Clarion Island, Revillagigedo Archipelago, Mexico. The Wilson Journal of Ornithology, 121(4), 745-751. Wellicome, T.I., Fisher, R.J., Poulin, R.G., Todd, L.D., Bayne, E.M., Flockhart, D.T., Schmutz, J.K., De Smet, K. & James, P.C. (2014). Apparent survival of adult Burrowing Owls that breed in Canada is influenced by weather during migration and on their wintering grounds, The Condor: Ornithological Applications, 116(3), 446-458.

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