Stressors/Threats

Relevance to Species

HABITAT LOSS

breeding

Breeds in areas with low or no vegetation, large open areas such as agricultural fields and "wasteland"; historic breeding areas were largely associated with prairie dog towns, and burrowing owls have lost habitat with the widespread eradication of prairie dogs and other burrowing rodents. Loss of breeding habitat is considered to be the most critically important threat, as areas that support burrowing owls in Arizona are largely private lands that are being developed. Need to have several suitable holes in close proximity, plus some structural diversity such as trees, poles, fences for perching.

dispersal

loss of areas with holes for roosting may be significant. Can use areas that are not as open as breeding areas, and has remarkable ability to find holes.

foraging

size of foraging area is unknown, may be related to available food supply, differs seasonally and in life cycle of species; diversity of resources is important

wintering

winters in this area, needs foraging and roosting sites, some winter on breeding area, others move about and settle in new areas either temporarily or for a longer period

migratory stops

roosts in holes for days to weeks during migration and dispersal; Santa Cruz River is a migratory corridor

diurnal preferences - day, temporary

may use some short term roosts

diurnal preferences - day, long-term

generally remains near its burrow; forages by day in general vicinity of burrow

diurnal preferences - night

probably remains in its burrow

fire threat

fire may improve habitat by clearing vegetation; unintended fires may result in loss of habitat

HABITAT ALTERATION

prey

Consumes diverse prey: insects, rodents, small birds. Habitat diversity provides for a variety of prey items, anything that reduces diversity is bad.

nest sites

uses holes in the ground, ranging from rodent burrows to solution cavities, other erosional features, and artificial burrows, but value of artificial burrows has not been well researched

HABITAT ALTERATION continued

vegetation composition/density

prefers low density vegetation, but some locations have had higher density, especially for wintering locations; needs some vegetation species and structural diversity

habitat conversion

much of this species current habitat is being developed for housing and that is not suitable, or not as suitable, as agricultural lands; mesquite and bufflegrass invasion may also be a problem on inactive agricultural lands

escape cover

needs some protection from raptors; females use burrows, males use shade

fragmentation

appears to adapt well to a fragmented environment by finding suitable patches that are spread across the landscape; extent and degree of fragmentation that this species can tolerate is not known

invasive plant species

invasion by mesquite and bufflegrass is probably bad for this species, there have apparently been losses of burrowing owls in the Avra Valley that are contemporary with mesquite and bufflegrass invasion of inactive agricultural fields

invasive animal species

unknown

habitat rehabilitation potential

probably good, uses a variety of developed areas, but the widespread use of artificial burrows has not been studied over time; control of invasive plants may be beneficial

contaminants

unknown

nutrient enrichment

probably irrelevant

water accessibility

not considered a problem

drought

may result in reduction of prey populations

flood

may have adverse effects on burrows and prey

groundwater depletion

not considered a problem

root zone water loss

not considered a problem

artificial water sources

not known to use

infiltration

not a problem

runoff

may result in flooding of burrows or prey burrows

edge effects

Edges are not considered good, this bird prefers large blocks of open habitat with few perches for larger raptors

HABITAT ALTERATION continued

water quality - turbidity

apparently irrelevant

water quality - salinity

apparently irrelevant

water quality - conductivity

apparently irrelevant

water quality - dissolved oxygen

apparently irrelevant

water quality - effluent

apparently irrelevant

sheetflow disruption

may result in eventual improvement of habitat on downstream side by allowing rodents to invade areas that had previously been flooded; may also be detrimental on upstream side by encouraging mesquite and bufflegrass invasion

flow rate

apparently irrelevant

land use history

prefers areas of open land, such as inactive agricultural fields

roads - dust

not considered a problem

roads - erosion

may benefit by creating burrows, but may also result in loss of burrows

roads - surface water diversion/ponding

may result in eventual improvement of habitat on downstream side by allowing rodents to invade areas that previously flooded; may be detrimental on upstream side by encouraging mesquite and bufflegrass invasion

roads - asphalt/contaminants

unknown

SPECIES CHARACTERISTICS

dispersal mechanism

uses burrows that it finds during dispersal flights, sometimes in habitat that may not be suitable for long term residence

behavior traits

tends to be a conspicuous target for shooters and raptors

habitat rehabilitation potential

may be fairly easy to create and/or rehabilitate habitat, but concern is that good BUOW habitat is not good for some other species of concern or especially aesthetically pleasing, plus continued vigilance against invasive species is needed.

colonization potential

known to be able to locate isolated areas of suitable habitat

effective population size

unknown

SPECIES CHARACTERISTICS continued

total population size

unknown but thought to be declining because of habitat loss

fecundity

not considered a problem

knowledge/data on species

essentially nothing is known about demographics or population dynamics

seasonal specialization

not considered a problem

captive breeding/translocation potential

translocations are practiced widely, but not adequately studied

genetic isolation

unknown

inbreeding

unknown

diurnal specialization

not considered to be a problem

off-site mortality - migratory

no information is available

off-site mortality - from surrounding land uses

no information is available

breadth of resource use

prey is plentiful and diverse, but concentrations of prey animals are patchy; nesting and roosting habitat is uncommon, declining, and critically important

sensitivity to disturbance

considered sensitive to disturbance, although some individuals habituate to frequent disturbance

adaptability

fairly limited in habitat selection

charisma

Fairly charismatic and popular

INTERSPECIFIC FACTORS

predation

Highly susceptible to predation by raptors, does not thrive in areas with high raptor concentrations or perches for raptors

disease

susceptible to West Nile Virus and known to be killed by it, but effects of WNV on individuals and populations is unknown at present; other diseases are unknown

pollinators/seed dispersers

NA

competition

may be subject to competition for burrows from rock squirrels and snakes

brood parasitism

not considered a problem

domestic/feral animals

may be preyed on by cats and harassed by dogs

invasive species

effects unknown, invasive plants alter habitat adversely

ANTHROPOGENIC FACTORS

edge effect

prefers large blocks of relatively barren soil or low vegetation, does not benefit by edges, and may be harmed if edges attract raptors

disease

unknown, but see above

fire threat

fire may improve habitat by clearing vegetation; unintended fires may result in loss of habitat

off-road vehicles - dust

not considered a problem

off-road vehicles - erosion

possibly may result in habitat loss, crushing of burrows or impacts to prey

off-road vehicles - noise

disturbance may be a problem if frequent

mining

not considered a problem

passive recreation

not considered a problem

grazing - vegetation impacts

may be beneficial if it prevents growth of new vegetation

grazing - soil impacts

not considered a problem

collection/hunting

not considered a problem, except illegal target shooting

herbicides

not thought to be a problem, except as they may affect prey base

insecticides

not thought to be a problem, except as they may affect prey base

pesticides - impacts to species

not considered a problem, species is short-lived, does not have a known bioaccumulation problem

pesticides - impacts to prey

insecticides may reduce prey base; historic use of rodenticides led to loss of prairie dogs and decline of this species; present use of rodenticides may be a serious problem for this species

direct take/mortality

not considered a problem

noise

may be a problem if frequent disturbance occurs

light

effects unknown, not considered a problem

movement

may be a problem if frequent disturbance occurs

ANTHROPOGENIC FACTORS continued

landscaping

could be beneficial if low density vegetation and minimal raptor perches are part of the landscaping of large sites; known to do well in some parks, parkways, and golf courses

invasives

buffelgrass may be bad, mesquite invasion is bad

domestic/feral animals

may be a problem, especially predation by cats

dumping

not considered a problem

undocumented immigrants

may cause repeated disturbance in nesting areas

increased road density

not considered a problem except that it may result in loss of habitat

road kill

may be a problem, not well documented

electrocution on powerlines/towers

not considered a problem but birds may occasionally collide with towers

CONNECTIVITY

fragmentation

lives in a fragmented landscape, but prefers fairly large blocks of open country

barriers

unknown

traffic volumes

not considered a problem

wash incision

may be beneficial if it results in creation of new habitat, and may be harmful is burrows are lost

corridor width

probably irrelevant

habitat patchiness

good habitat is large patches of minimal vegetation

riparian/upland connection

not considered a problem, except if "restoration" is done in a way that causes loss of burrows and habitat

road crossings

not considered a problem

road width

not considered a problem

vegetation next to roads

may be a problem

Stressors/Threats

Relevance to Species

HABITAT LOSS

foraging

size of foraging area is unknown, but will forage over large distances; thought to prefer "edges" of habitat

wintering

winter roosts are generally caves or mines, threatened by closure

migratory stops

roosts are necessary for migrants

diurnal preferences - day, temporary

unknown and unlikely

diurnal preferences - day, long-term

caves and mines are extremely important

diurnal preferences - night

needed, includes bridges, buildings, drainage culverts?, and other unknown

fire threat

probably minor

HABITAT ALTERATION

prey

moths, 3-10 mm, Noctuidae; but includes other insects; loss of prey= loss of bats

nest sites

maternity roosts critically important

vegetation composition/density

important as source of prey; protect riparian and other edges

fragmentation

potentially does not matter, it lives in a fragmented landscape

invasive plant species

unknown, probably affects prey base

habitat rehabilitaion potential

limited for roosts; conditions needed are generally unknown; gating roosts could be beneficial

contaminents

unknown; there is some indication that bats can acquire toxic materials in roosts, and considerable evidence that some species can acquire toxic doses of insecticides by consuming contaminated prey

water accessibility

drinks from and forages over water; very small water sources are used, large water bodies have not been surveyed; could benefit by vegetation around water

artifical water sources

drinks from and forages over water; very small water sources are used, large water bodies have not been surveyed; could benefit by vegetation around water

edge effects

prefers foraging along edges

fire threat

may affect prey

water quality - turbidity

broadly tolerant of water quality

flow rate

may prefer still or slow moving water

roads - surface water diversion/ponding

may be beneficial

SPECIES CHARACTERISTICS

behavior traits

sensitive to disturbance at roosts

habitat rehabiitation potential

potential to increase prey base; could benefit by gating mines and caves; experiment with creating habitat?

fecundity

1 young per year, fecundity is low as with most bats

captive breeding/translocation potential

no success with moving from roosts

inbreeding

very low variability suggests inbreeding or small gene pool

off-site mortality - from surrounding land uses

could be driven from areas by renewed mining, urban expansion, human disturbance

sensitivity to disturbance

highly sensitive; outreach to recreational cavers and mine explorers is needed

adaptibility

not very adaptable to some changes, especially loss of roosts

charisma

mixed bag: bats have had a major change in public image in past two decades but some people still fear or hate; need to empasize that they eat pest insects

INTERSPECIFIC FACTORS

predation

limited knowledge; may be subject to predation by cats but this is not likely

disease

rabies may affect; others unknown

competition

unknown; has been found in roosts with other species

domestic/feral animals

may be preyed on by cats, but this is not likely

ANTHROPOGENIC FACTORS

edge effect

edges are prefered foraging sites

off-road vehicles - dust

ORVs may be a problem because they get people to roost sites and result in disturbance

mining

renewed mining in areas with old mines may result in disturbance or loss of roosts

passive recreation

disturbance of roosts; should route trails to avoid roosts

grazing - vegetation impacts

may affect prey base

collection/hunting

not thought to be a problem

herbicides

not thought to be a problem, except as they may affect prey base

insecticides

impacts have been reduced over time, but still may be a problem

pesticides - impacts to species

impacts have been reduced over time, but still may be a problem

pesticides - impacts to prey

this could be significant

direct take/mortality

little effect except from mine hazard abatement practices, which could be serious impacts; road paving and de-icing may affect

light

bright lights near roosts may affect

landscaping

native plants could provide beneficial opportunities for habitat improvement

dumping

may affect if in roost sites

undocumented immigrants

may affect when they use caves and mines for shelter or dumping grounds

increased road density

may be a problem, low-flying bats could get hit by cars while foraging along road edges

road kill

may be a problem, low-flying bats could get hit by cars while foraging along road edges

CONNECTIVITY

barriers

large cities with abundant lights could be barriers

traffic volumes

increased volume could lead to increased road kill

wash incision

could create roost sites but could also take some away

corridor width

buffers along washes would be good but width unknown

habitat patchiness

depend on what is around them; patchiness could be good because it could increase insect diversity

riparian/upland connection

bridges could be improved as bat roosts

road crossings

could be opportunity for foraging or hazard due to roadkill

vegetation next to roads

could be opportunity or hazard; recommend not planting edges along larger and faster roads, allow space between trees and roads