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  • House hunting in the Santa Cruz: County effort is for the birds

    Jan 11, 2019 | Read More News
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    File: Santa Cruz bird surveyIt’s a cool, clear January day. A few clouds hang in the air, remnants of a storm the day before, and the late morning sun has burned off a heavy fog bank that had draped over much of Tucson since before dawn. Two men head down into the Santa Cruz River channel near the confluence of the Julian Wash, hunting for birds. 

    These hunters aren't carrying shotguns, however. They're armed with field journals and GPS monitors.  Harris Environmental wildlife biologists Lirain Urreiztieta and Scott Blackman are seeking bird nests before the Pima County Regional Flood Control District begins the next phase of a massive sediment removal project.

    January falls outside of bird breeding season but the District still contracted with Harris Environmental to survey the project area to ensure the work would not severely affect the avian residents of that reach.

    “Some bird species, such as curve-billed thrashers, potentially may begin nesting this early,” Urreiztieta said. “When we went out ahead of the Grant-to-Speedway phase of the sediment removal project it was during breeding season and we saw a high concentration of Abert’s towhee nests. We’ll probably see some nests from last season, made by mourning doves, verdins, cactus wrens.”

    The Flood Control District tries to schedule major projects to minimize the amount of wildlife mitigation required and plans for each phase of the Santa Cruz sediment removal work and identifies stands of desirable vegetation to be preserved. Plans also call for the removal of invasive plant species that could contribute to flooding or hamper an emergency response or maintenance efforts.

    File: Santa Cruz bird survey“What we do is take the spatial data and use it to mark the locations of the nests we find and create a map that the County can use to overlay with its data and if there are any active nests outside those ‘preserve in place’ areas they might consider expanding those little islands,” Urreiztieta said.

    The Pima County Regional Flood Control District expects to remove approximately 160,000 cubic yards of sediment from the bed of the Santa Cruz in this phase of the project, between Silverlake Road and Speedway Boulevard.

    “The point of our work is to help ensure the protection of our natural resources. We live in a community that values wildlife. The Santa Cruz is an important habitat for birds and it provides an open green space inside the city,” Urreiztieta said.

    “It’s also important from a compliance standpoint,” Blackman said. “It ensures the County meets the requirements of the federal Migratory Bird Treaty Act, which protects nearly every species of bird that lives in the Sonoran Desert. Only the house sparrow, rock dove, and European starling are not covered because they are non-native and considered invasive.”

    As they make their way downstream in the muddy channel, Urreiztieta and Blackman thoroughly scan the landscape. Trees, bushes and grassy areas all may hide nesting sites, depending on the type of bird. Some species prefer ground-level residences while others like the high life. Each nest they find gets classified as either “active,” “inactive” or “unknown”; its precise location marked by a GPS unit and recorded in a journal.

    “They are opportunistic,” Urreiztieta said. “They use the material that’s available. How complicated or well-woven a nest is varies by species. My favorite is the spherical nests that verdins make. It’s a perfect sphere with a little entryway near the bottom. They secure them well and use them year after year.”

    Some birds may nest year-round, others only during the breeding season. They can get territorial, usually with members of their own species.  Breeding season in Southern Arizona usually runs between March and August, peaking locally between late April and July.

    “Since we warm up more quickly here and this week it’s going to be approaching 70 degrees, it’s almost like Spring’s arriving,” Blackman said. “So birds get active here earlier than other parts of the country. Thrashers do start courting and nest-building early. I started seeing some of that in December.”

    The District took over maintenance responsibilities for the Santa Cruz from the City of Tucson in 2014. The project’s goal is to increase the Santa Cruz’s capacity to contain large floods. A buildup of sediment over the last 30 years has significantly reduced the volume of water the river can contain, with over 10 feet of buildup in some spots. Once sediment removal is complete, the District will monitor the river and perform minor maintenance work approximately every five years, depending on flood activity.

    File: Santa Cruz bird survey“Typically we do our nest surveys beyond the breeding season but what we want to do, no matter what, as part of our permitting process is to have our biological components done in advance and that includes reptiles and our bird surveys,” Mike Cabrera, Flood Control District Permit and Regulatory compliance officer, said. “This is such a high-priority area, not just for flood control but for the public. People use The Loop all the time and we want to make sure we’re being sensitive to the environment.”

    “One of the benefits we have on this project is using the Multi-Species Conservation Plan’s Section 10 permit,” Cabrera added. “This reach of the Santa Cruz doesn’t have any threatened or endangered species but there may be species covered under the MSCP that go beyond the requirements of the Endangered Species Act. Harris did a survey for the first phase of the sediment removal project last spring and so they were familiar with our needs for this phase. They are great at what they do.”

    Urreiztieta and Blackman's hunt proved productive. Over the course of two days, they located 85 nests — all inactive — between Silverlake and Speedway, including 53 verdin nests.