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US Fish & Wildlife Service FieldNotes

KERN NWR: Wetland Floodling Brings Life to Tricolored Blackbird Nesting Colony

Region 8, July 30, 2009
Creche of juvenile tricolored blackbirds. (photo: Scott Frazer, USFWS)
Creche of juvenile tricolored blackbirds. (photo: Scott Frazer, USFWS) - Photo Credit: n/a
Tricolored blackbird. (photo: USFWS)
Tricolored blackbird. (photo: USFWS) - Photo Credit: n/a

by Scott Frazer, Kern National Wildlife Refuge
Rapid action to supply water for nesting Tricolored blackbirds achieved dramatic results at a large and significant Tricolored blackbird (TRBL) nesting colony in the Tulare Basin of central California.  Due to a freeze on state expenditures this spring, contracts with private landowners paying for water and specific wetland management activities were suspended just at the time that migrating TRBL were establishing their nesting colony.  U.S. Fish and Wildlife Service (USFWS) Migratory Bird Program funds were made available as a miniature stimulus package for nesting birds.

 

Tricolored blackbirds are a species of special concern and petitions to list this species have been submitted to USFWS in the past.  Tricolored blackbirds are considered an itinerant breeder with highly variable colony locations from year to year.  However, insect abundance and close proximity to water are important factors influencing nest site selection and reproductive success. 

 

This private wetland located in Kern County near Wasco, Calif., has been an unusually reliable and productive TRBL colony for each of the past three years.  It appears to meet all of the criteria for reproductive success.  Dense cattail vegetation attracts nesting TRBL.  The wetland has been managed under a Landowner Incentive Program (LIP) contract with California Department of Fish and Game (CDFG) to hold water during the nesting season and is located close to annual grasslands, irrigated alfalfa and dairies that provide large insect populations an important, high protein food sources.  By February of 2009, CDFG biologists had informed LIP contract holders that they would be unable to assure contract payments due to the state‚Äôs budget shortfalls.   Without contract payments, landowners were unable to provide supplemental water. 

 

In recent years, most of the TRBL colonies in the Central Valley of California are located in dairy silage cropland.  Nesting colonies located in crop fields that are routinely harvested prior to juvenile blackbirds fledging sets up a conflict with agricultural producers who need to harvest silage before it dries in the summer sun.

 

When the Partners for Fish and Wildlife biologist at Kern NWR considered potential impacts the lack of water would have on TRBL nesting on the LIP property, a short term funding request was submitted to the Region 8 Migratory Bird Chief.  Marie Strassburger agreed that keeping one TRBL colony nesting in natural habitat was a proposal worth supporting.  The Region 8 Migratory Bird Program provided funding for 80 acres of flooded wetland or 50 percent of the existing LIP contract area.   

 

TRBL had already begun nesting in dry cattails before the agreement to fund water purchases was implemented.  Due to the prospect of a reproductive failure, assistance was obtained from California Audubon to speed up purchase of supplemental water.  Quick action by both California Audubon and USFWS accomplished everything biological staff monitoring the TRBL had intended and more.  The TRBL colony developed and expanded in size during the typical 45 to 60 day nesting season.  Nest establishment often occurs in April with fledgling young present by early June.  This year by the end of June and continuing into July, it became obvious that many TRBL were breeding locally in a second sequential nesting attempt that also fledged young TRBL.  Typical annual migrations by TRBL include a first nesting attempt in the southern San Joaquin Valley with subsequent nesting attempts made after moving north to the Sacramento Valley.

 

This story ends with positive news that TRBL have moved north to follow the path of migration that they have followed for all of recorded history.  Next year there may be new challenges, but Tulare Basin Tricolored blackbirds will have one more successful reproductive effort behind them.

 

 

 

 

Contact Info: scott frazer, 661 725 2767, scott_frazer@fws.gov