California drought putting fish, birds and tree species at risk, scientists say

California’s drought is imperiling tricolored blackbirds, large trees and native fish, with some of the affected species already on the state’s endangered list and others likely headed there because of rapidly declining numbers, scientists say.

“The problems created by the drought are just a harbinger of things to come,” said Peter Moyle, a professor at the UC Davis Center for Watershed Sciences, which hosted a daylong Capitol summit Friday on economic and environmental costs of the drought.

“Native fishes and the ecosystems that support them are incredibly vulnerable to drought,” Moyle said. “There are currently 37 species of fish on the endangered species list in California – and there is every sign that that number will increase,” he said.

Eighty percent of those species face extinction by the year 2100 if present trends continue, Moyle said.

Native fish are able to weather natural drought years, but the development of the state’s water system has created the equivalent of perpetual drought conditions for many species, he said.

The state has 47 animal species on its endangered list, another 36 listed as “threatened,” plus six that are candidates for inclusion on one of the lists, according to the state Department of Fish and Wildlife.

One species that could end up on the candidate list is the tricolored blackbird, said Robert Meese, of UC Davis’ Department of Environmental Science and Policy.

“The tricolored blackbird may not be on the endangered list yet, but the drought is definitely having an effect,” Meese said. “The birds have not been reproducing.”

Reproduction declines have been noticed since 2007, before the drought, Meese said, but recent counts have shown even steeper declines. A statewide survey of tricolored blackbirds, known for their red shoulder patch with a bright white stripe, was recently concluded and the results are due out in three weeks.

“I suspect that survey will be on the order of 120,000 birds,” Meese said. “That is less than half of what was seen in 2011, and about 75 percent less than what was seen in 2008.”

At issue for the birds is a lack of insects since female birds require insects in their diet to form eggs. Also, young birds require insects during the first nine days of life, when they cannot digest plant material. Meese contends that the effects of the drought have created lower populations of insects, as well as less-extensive wetlands from which blackbirds can feed.

A perfect storm of pesticide use, drought and urban development is putting a lot of pressure on the tricolored blackbird, Meese said. Unlike the red-winged blackbird, the tricolored is a colonial species that tends to stay close to home when hunting for insects – in most cases it will not fly farther than three miles.

Meese has seen colonies in the Central Valley this year that are only a quarter of the size recorded last year – only 5,000 birds. Still, a shortage of the insects they feed on remains an issue in the bird’s territory.

“If you put that many mouths in a small area, that puts an intense pressure on the landscape to produce insects for that many birds,” he said.

It is not only fish and birds that are threatened by the drought, the scientists said. Large trees have been profoundly affected, especially in the West, a recent study found.

The study, conducted by researchers from the U.S. Geologic Survey and others, looked at tree mortality in the Sierra Nevada and found increased mortality as a result of drought and increased temperatures. The study established a link between tree mortality at low elevations and water deficits.

Andrew Fulks, who manages UC Davis’ Putah Creek Riparian Reserve, has seen the drought affect a tree closer to home – the foothill pine. The tree, native to California, prefers to grow in open woodlands in the 1,000- to 4,000-foot elevation range.

“We have seen more mortality in Yolo County due to drought stress,” he said. “The tree has been unable to fend off the dwarf pine mistletoe, which weakens the tree enough to allow it to be killed by it and the bark beetle.”