CITY OF TUCSON

HABITAT CONSERVATION PLAN

Burrowing Owl Subcommittee

Meeting Notes

Topic: Stressors and threats to Burrowing Owl

Date: May 9, 2005, 1 p.m

Location: Arizona Game and Fish Department office

Participants: Mike Ingraldi, Arizona Game and Fish Department Research Branch; Mark Ogonowski, University of Arizona; Marit Alanen, U. S. Fish and Wildlife Service; Wendy Burroughs, Pima County Parks and Recreation Department; Ken Kingsley and Leslie Liberti, SWCA

The consensus of the group was that burrowing owls had been severely impacted by the historic loss of prairie dogs throughout their range. Prairie dogs were not known to have been present in Tucson or Pima County, but have largely been eradicated from southeastern Arizona and most of their historic range throughout the nation. Today the primary threat is development of housing in areas that were agricultural or vacant land. Translocation of birds to new areas with artificial burrows is the standard mitigation method, but the results of this procedure have not been studied adequately.

Burrowing owls are known to occur, or to have occurred, throughout all of the City of Tucson HCP planning areas. They are known to occur at highest densities along the Santa Cruz River, in steep-sided embankments with adjacent open land. The current concept of riparian restoration for the Santa Cruz River corridor is likely to be harmful to burrowing owls that are there.

They are also known to occur in Avra Valley, at low densities, with the highest numbers in creosote flats near agricultural lands. In the Avra Valley, they appear to have declined from about twenty years ago, perhaps as a result of vegetation growth, especially mesquite invasion, on retired agricultural land. The Avra Valley lands appear to offer high hopes as burrowing owl habitat, if they are managed to control or reduce invasion by buffelgrass and mesquite. Development and management of water projects could accommodate this species well. The habitat could be improved if it were managed to encourage burrowing rodents, especially round-tailed ground squirrels, which are an important prey species.

In the Southlands, the only known individuals have been radio tagged wintering birds moving through the area and remaining only a few days. Conditions in the Southlands area do not appear to be well-suited for this species because of abundant raptor perches, edaphic conditions generally not good for burrowing, and low prey populations.

The consensus was that this species prefers low density, high diversity vegetation. They use several burrows, not just one. Burrowing owls are “mesopredators” that consume a variety of insects, small mammals, and birds, and are consumed by raptors, especially migrating red-tailed hawks. Large mammal manure spread near nests appears to benefit this species, either by deterring predators or by attracting potential prey.

Burrowing owls appear to be sensitive to direct disturbance, as by people passing near their burrows, but they are not especially sensitive to noise, as from roads. They are know to use culverts as roosts, and to be occasionally hit by cars. For areas that are going to have multiple use trails, it would be best to restrict the trails to just one side of the wash and leave the other side undisturbed for wildlife, including burrowing owls.

Burrowing owls are said to be susceptible to West Nile Virus, but no other diseases are known for them.

Very little is known about their population biology and the effects of various anthropogenic factors. It appears that this species has had to undergo a major change in its biology and distribution, with the loss of prairie dogs, and it is not moving into and adapting to different situations than its historic habitat. Its future is entirely unknown.

See attached table for specific points.