Tricolored blackbird. (photo: USFWS)

 by Scott Frazer, Kern National Wildlife Refuge     

Changes in habitat conditions have not been good for tricolored blackbirds, a species of special concern.  In California’s dry southern San Joaquin Valley, life can be tough for this colonial nesting species of blackbird that has traditionally nested near or over water in wetland habitats.

Tulare Lake basin in the southern San Joaquin Valley historically held vast tracts of seasonal wetlands used extensively by tricolored blackbirds. Large wetlands that once provided abundant dense nesting cover as well as food sources for the birds have mostly dried up.  With fewer natural places to nest, tricolored blackbirds in California are adapting by going to the state’s dairy farms to establish colonial nest sites.  Nesting birds in croplands often puts them in conflict with farm operations, creating a dilemma for farmers and bird biologists   U.S. Fish and Wildlife Service is working with agricultural producer to find solutions to this dilemma.  

Use of agricultural silage fields as nesting sites may conflict with time for routine harvest.  Crop fields are often ready to harvest a few days to several weeks before juvenile tricolored blackbirds can fledge from nests.  Short delays in harvest have been arranged which saved both the valuable crops and immature birds.  Longer delays that reduce crop values may be negotiated if funding is available to buy replacement livestock forage.  Communication with dairy farmers is the starting point and each arrangement is unique.

Working with California dairy farmers to protect nesting colonies will help tricolored blackbirds survive in a changing landscape.  You know those "happy California cows” live on dairies that make tricolored blackbirds pretty happy too.  There is always water around a dairy.  The birds can find dense nesting cover in silage fields, as well as plenty of insects high in protein needed during egg production and to support young hatchlings.  This combination of desirable conditions has attracted tricolored blackbirds to establish nesting colonies on dairies in the Tulare basin every year now.

Work to protect tricolored blackbird colonies on dairies in the Tulare basin began in March with surveys along county roads. While tricolored blackbirds often use sites close to locations of past colonies, conditions vary considerably from year to year.  The tricolored blackbirds are considered “itinerant” breeders responding to annual variations in food supply and available nesting cover.  The dynamic nature of agricultural cropping patterns results in new locations for tricolored blackbird colonies almost every year.  Some general areas appear to be attractive on a recurring basis, but it is impossible to predict exactly where tricolored blackbirds will show up on any specific breeding season.

Inspired by the high reproductive success at a Kern county dairy that has repeatedly produced tricolored blackbird colonies, biologists from Kern National Wildlife Refuge and University of California at Davis are confident that tricolored blackbirds will have better reproductive success during 2008 in Tulare Basin than they did in 2007.  In fact early successes at several natural and agricultural TRBL colony sites in the Tulare Basin appear to have more fledgling tricolored blackbirds produced than all documented reproductive success statewide in 2007.

Additional success in 2008 included protecting the largest single known tricolored blackbird colony with 80,000 adults in a dairy silage field.  Cooperative efforts by the dairy operator delayed harvest in exchange for reimbursement of costs for one additional irrigation needed to extend crop maturity.  Paying one irrigation cost is a very economical method of preventing the destruction of thousands of flightless juvenile tricolored blackbirds.  Another dairy silage field with several hundred tricolored blackbird nests was protected by communicating the need for approximately one week delay in harvest which was accommodated by the dairy operator.

How are dairy farmers and conservation organizations working together?  Once a tricolored blackbird colony has been identified, USFWS biologists approach the private landowner and seek permission to monitor bird use in the field.  The number of tricolored blackbirds present and the stage of reproductive activity are documented to determine if routine harvest of a silage crop will impact the colony.  The construction of new nests and progress in egg laying is observed and used to determine the stage of nesting chronology.  Projected routine harvest dates are compared to when tricolored blackbirds could mature and fly from nests. 

In most cases a short delay in harvest is needed to allow protection of the tricolored blackbird young.  Monetary compensation has been offered to dairy operators for delaying harvest to buy time for tricolored blackbird colonies to complete the reproductive cycle.  When the delays of harvest exceed two weeks most of the value of the silage crop is lost, purchase of the crop to conserve large TRBL colonies is an expensive activity supported by multiple organizations.

In addition to USFWS, conservation efforts in the Tulare Basin have been given a boost from Audubon California, California Departments of Fish & Game and Food & Agriculture, Geyer Associates, Sustainable Conservation, Tulare County Resource Conservation District and the Farm Bureau.  Audubon California has pitched in with funding, administration of funds and monitoring of tricolored blackbird populations.

Biologists are sometimes asked “How many tricolored blackbirds are there in the world?”  The answer is approximately 300,000 to 400,000 adults have been documented respectively during the last two big censuses in 2005 and 2008.  The concern for these birds continues as they struggle to find a place to survive in the complex landscape that is Central California.  Agricultural lands have become the home to many tricolored blackbird colonies because water for wetlands is in limited supply.

Hope springs eternal that “Happy California Cows” will help sustain happy tricolored blackbird colonies that can continue to complete reproductive cycles assuring the survival of this puzzling species.

More information on tricolored blackbirds in California is available on the Web at:

UC Davis Tricolored Blackbird Portal