Final Results in for April Tricolored Blackbird Survey!

A major goal for this year was to expand coverage by distributing volunteers widely across the State, especially to areas local experts knew of as historic colony sites. Many volunteers were able to contribute local knowledge and added a significant number of colony sites to our list, each of which is now added to the online database (http://tricolor.ice.ucdavis.edu). We encourage you to add any future observations you make of Tricolored Blackbirds in your area to this online database.

Volunteers were able to visit 361 known or newly discovered colony sites in 43 counties across California and in southern Oregon. Our total count for this year was just under 395,000 birds! This is over 100,000 more birds than were counted in 2005. Although this is great news, it is certainly not the result of a real increase in population size. The breeding season for 2007 was not a good one for Tricolored Blackbirds with drought conditions leading to widespread colony failures. The larger number of birds counted this year is testament to the increased effort by all of our volunteers, covering more areas across the state. This year’s survey tells us that there are definitely more birds and colonies out there than previously estimated.

However, most of these birds are concentrated in a few very large breeding colonies in the southern Central Valley in Merced, Kern, and Tulare Counties. In these areas they have become accustomed to using grain fields associated with dairies as breeding colony sites, leaving them vulnerable to reproductive failure when harvest occurs before young leave the nest.  Audubon California in May struck a deal with a local farmer to save one of the larger breeding colonies, but this will continue to be an issue.

In addition, many volunteers surveyed new and historic sites across southern California this year, where this species has declined most dramatically. We had hoped to find many more birds than previously reported, but this year’s results confirm that this species only occurs in very small numbers and may be on the verge of extirpation in Southern California. The total count for southern California was 5,599 birds (less than 2% of the statewide count in nearly 20% of the counties surveyed).  What makes this more alarming is that the population in Southern California may be genetically distinct from birds in the rest of the state. A genetic study is currently underway at UCLA to test this. The data collected by volunteers this year has been a great help to the UCLA team in identifying colony sites from which they could collect genetic material (no live birds were captured for these samples).

Audubon California and the rest of the Tricolored Blackbird Working group continue to work with landowners and agencies to protect this species. There is much reason for hope and the volunteers for this survey are a critical part of our conservation efforts. Thanks again to all the volunteers!

Rodd Kelsey

Audubon California