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Environment & Science

Drought contributing to decline of the tricolored blackbird

Photo by Alan Vernon via Flickr Creative Commons

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The tricolored blackbird was once the most abundant bird species in southern California. But disappearing wetlands have destroyed much of the birds' habitat and the current drought is making the situation worse.

With its distinctive red and white stripe on the males, the species is truly a California resident with 99 percent of birds making its home in the state.

Take Two co-host A Martinez talked to Bob Meese, staff research associate at U.C. Davis' Department of Environmental Science and Policy.


How would you describe the tricolored blackbird?

It’s unique because it is a colonial species of blackbird. It’s closely related to the familiar red-winged blackbird. Rather than nesting sparsely and in very large territories it nests in very dense colonies with territories the size of a typical desk in an office.

 Why is it special to California, with 99 percent of the species here?

We think it’s because of the conditions that used to exist in the Central Valley where there were just huge vast wetlands and we expect that those wetlands provided perfect nesting habitat as well as insects for foraging and they require insects in order to form eggs and feed their nestlings.

How are they being affected?

The wetlands aren’t wet; they’re quite dry. The effect that has on the birds is they find that unattractive and they’ll probably be shunning most of the wetlands in the Central Valley and possibly some in southern California this year.

When did you notice the problem with blackbirds?

We’ve known for decades. The original work, which was intended to assess the status of the population, occurred in the 1930s and we’ve been working on and off with the species ever since. But the current decline is probably more rapid than any that’s been documented previously and is known to be largely due to the fact that the birds are producing very, very few young.

The problem in terms of numbers:

The population estimate around 1930 would be about 3 million birds and that was from Baja to Oregon. Right now was [a study] derived from the statewide survey and that was about 258,000. But we are going to be conducting another statewide survey in about a month and I predicted that we are probably going to see less than 100,000 birds.

When would it be labeled endangered?

That’s as much a political decision as it is a biological one but based upon my conversations with my colleagues with state and federal agencies I think if they see the number go below 100,000 they’re probably going to enter into immediate conversations about what they want to do about it.

Birds are now moving into grain fields. How are farmers dealing with that?

There is a volunteer program funded by the NRCS (Natural Resources Conservation Service) that provides funding for the farmers to not harvest their grain fields during the time when the birds are present.

The birds have just started nesting. How successful do you think they’ll be this season?

The most recent drought was between 2006 and 2007 and the 2007 breeding season was horrible. For example, one colony in Kern County consisted of 50,000 birds and in the course of two days all the birds in that colony disappeared. They simply abandoned the nesting attempt. I went into the colony … and looked and there were literally thousands of nests with no eggs in any of them. If they haven’t eaten enough insects they simply can’t form eggs and after a certain period of time they simply give up.

These conditions are grim. Are they salvageable?

Oh sure. I’m pretty concerned because we have not been able to stem the decline yet. I think this year is pretty much going to be a bust in terms of reproductive success for the species. The birds just can’t go too many more years with very, very poor reproduction before it gets truly rare. We could easily see it go from 100,000 to 50,000 over a period as short as three years. So we do need to stem the decline soon or else the bird is truly going to get into some sort of imperiled status.