Nature

How Birds Preserve the Pajaro River Levees Secure


The Pajaro River slithers between the cities of Pajaro and Watsonville, which lie straight inside the river’s pure floodplain. Though the river created the fertile soils that birthed this agricultural neighborhood, its floodwaters can wreak havoc on the area: a 1995 flood killed two folks and destroyed $95 million price of agricultural crops.

Levee managers battle a continuing battle with gopher and floor squirrel burrows, which weaken the dust embankments that line the river to guard the area from floodwaters. Most levee safety entails poisoning the animals, however the toxin-laden rodents change into lethal treats for predators. The poison cripples or kills bobcats, coyotes, and birds of prey, inflicting widespread animal struggling and lowering the inhabitants of carnivores wanted to naturally hold rodents in test.

Now, researchers and levee managers are testing whether or not merely attracting hawks and owls can hold rodent numbers down whereas supporting native wildlife. This system is inspiring different Bay Space municipalities like town of Santa Cruz to discover wildlife-friendly levee administration.

In 2019, levee managers for the Pajaro River discovered that their counterparts in Ventura County had changed rodenticide pest management with owl containers and hawk perches alongside a stretch of the Revolon Slough levee, yielding intriguing outcomes. The raptors weren’t solely simpler at controlling rodents, however additionally they saved the flood management company greater than $7,500 per mile of levee.

“It simply type of appeared like a no brainer for me. It appeared like a cool and accountable strategy to do our work, and if we are able to get sufficient birds on the market, then they’re working full time,” says Rusty Barker, a civil engineer with the Santa Cruz County Zone 7 Flood Management and Water Conservation District.

Pajaro River and floodplain
An aerial view of the Pajaro River, with the cities of Pajaro and Watsonville within the river’s pure floodplain. (Photograph by Robert Campbell – U.S. Military Corps of Engineers Digital Visible Library Picture, CC BY-SA 3.0)

On the Santa Cruz County facet of the Pajaro River, Barker’s staff had already changed rodenticides with carbon monoxide fumigation. Though this technique eliminates the ecological penalties of poisons by suffocating the rodents of their burrows, it additionally kills non-target species like salamanders and frogs that use the burrows for refuge. The extra profitable the raptors are at controlling the rodents, the much less that upkeep must resort to fumigation.

Barker approached his faculty buddy Zeka Glucs, director of the Predatory Chook Analysis Group at UC Santa Cruz, to see if they might staff up and take a look at the pure predator technique for the Pajaro River.

“This a part of the county may be very wealthy in birds, and raptors particularly,” Glucs says. “It’s nearly whether or not we are able to focus them in on this versus all the things else.”

Glucs and her college students put in wood nest containers for barn owls, that are voracious gopher predators. In addition they arrange excessive perches the place red-tailed hawks and great-horned owls can lord over the land and use their laser-focus eyesight to identify bigger rodents like floor squirrels. Attracting completely different raptor species in response to their favored prey is vital, as a result of though gophers are most typical, floor squirrel burrows are so in depth that they will lower clear by way of the levee. One behemoth floor squirrel burrow present in San Luis Obispo County stretched over 700 toes lengthy and displaced 5 tons of soil.

researchers check on a nest box
UC Santa Cruz Predatory Chook Analysis Group Director Zeka Glucs, volunteer Ben Drake, and UCSC undergraduate pupil Hannah Doniach put together to test on barn owl chicks within the venture’s nest containers. (Photograph courtesy of Zeka Glucs)

The human-made perches and nesting containers create a vertical habitat usually offered by bushes, however with out the hazard of bushes uprooting throughout floods and bringing swathes of levee with them. For this reason the levees are deliberately stored away from vegetation, Barker says, creating an imbalanced ecosystem the place rodents can thrive with out the watchful eyes of birds of prey to maintain them in test.

The researchers visited the levee web site to survey for rodent burrows and raptors by way of the pandemic. By gathering and dissecting owl pellets (bits of fur and bone coughed up by the birds), they have been capable of determine which species the owls have been devouring. Barn owls returned to nest within the containers every season, with three profitable nests in 2021. Every nesting pair preys on 1000’s of rodents to feed their rising household. 

Along with the success in bringing nesting owls to the positioning, Glucs and her staff discovered fewer rodent burrows alongside the two.5-mile stretch of levee with the raptor perches and owl containers. The hassle has additionally caught on. The Santa Cruz Water Division is working with Glucs to discover bringing the research to the San Lorenzo River in 2022, and Barker is working to develop the venture to the Pajaro River’s reverse financial institution, which is managed by Monterey County.

“There’s undoubtedly a whole lot of curiosity in our neighborhood about built-in pest administration,” Glucs says. “And it’s one thing I actually care about, as a result of rodenticide use is basically just like the DDT of our time.”

banding a barn owl chick
Golden Gate Raptor Observatory volunteer Anne Ardillo bands a barn owl chick raised in a subsequent field alongside the Pajaro River levee. (Photograph courtesy of Zeka Glucs)

Raptors affected by suspected poisoning hardly ever get well, says Amy Redfeather, a wildlife rehabilitator at Native Animal Rescue in Santa Cruz. Though the rescue middle has seen a decline in poisoned animals this yr, they’ve nonetheless handled greater than a dozen raptors with signs of poisoning.

“It doesn’t matter what we do — vitamin Ok, charcoal, fluids — it doesn’t matter what we do, they find yourself dying,” says Redfeather.

Anticoagulant rodenticides work by stopping blood clotting, and second-generation merchandise are significantly potent: they work slowly, permitting a rodent to eat concentrations far above a deadly dose earlier than perishing. The poison then persists within the lifeless animals for months and passes up the meals chain to something that eats them.

Though the state Legislature restricted family use of second-generation poisons in 2014, they continued for use by business operators and licensed applicators (in addition to illegally by different customers), and rodenticide poisoning in wildlife continued unabated. A 2018 evaluate of accessible analysis by the Division of Pesticide Regulation discovered that of all animals examined for rodenticide poisoning in California, over 75 % have been optimistic. Within the years following the 2014 restrictions, the poisons have been present in almost all mountain lions and bobcats examined in addition to 70 % of endangered northern noticed owls.

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The state handed a regulation increasing its restrictions that went into impact January 1, 2021. Nevertheless, the brand new regulation has exceptions for businesses that defend public well being, agriculture, and water provides. Whilst Pajaro River levee managers step away from rodenticide use, it stays widespread at different rivers across the state.

“Hopefully we are able to actually present that it’s an efficient program to implement,” Barker says. “There are a whole lot or 1000’s of miles of levees in California, and this isn’t an issue that’s remoted to us.”

Along with encouraging different levee managers to undertake wildlife-friendly rodent management, the analysis staff partnered with Watsonville Wetlands Watch and Raptors Are the Resolution to conduct outreach within the surrounding agricultural neighborhood, which continues to make use of toxic bait. If the analysis staff can exhibit that wildlife-friendly strategies are efficient and cost-efficient, farmers might make the swap, too.

“Hopefully we’ll have the ability to encourage people to encourage raptors,” Glucs says, “fairly than handicap them with rodenticides.”

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