A report by U.C. Davis ecologist Bob Meese in the spring, 2012 issue of California Fish and Game summarizes the effects of cattle egret predation on tricolored blackbird breeding colonies. Cattle egrets, which have only relatively recently expanded their range into California, have since 2006 been severely reducing the reproductive success of tricolor colonies within the foraging range of their rookery in Tulare County. This new report documents the impacts of cattle egret predation from 2006 through 2011 and considers the conservation implications of continued losses of tricolor productivity to cattle egret predation.
The results of the 2011 Statewide Survey have been released by Audubon California's Keiller Kyle, the survey coordinator.
The results show a dramatic drop in the number of tricolors statewide, from approximately 395,000 in 2008 to about 259,000 this year, a greater than 33% decrease, this despite an increase in the number of sites visited and an immense effort by 100 survey participants.
The results of this year's survey are summarized in a report from Kyle and Rodd Kelsey, the 2008 Statewide Survey coordinator. Download the report from the portal.
We thank the many volunteer observers for their dedication and hard work in helping to monitor the abundance, distribution, and breeding habitats utilized by the tricolor - California's blackbird.
Information for the Environment (ICE) staff at the University of California, Davis has recently upgraded the Tricolored Blackbird Portal to facilitate access to data, provide greater data input functionality, and to support the 2011 Statewide Survey and all future statewide surveys.
These enhancements include:
The 2011 Tricolored Blackbird Statewide Survey has arrived!!!
The 2011 statewide survey runs from Friday, April 15th through Sunday, April 17th.
Participants in the 2011 Statewide Survey should click here (http://tricolor.ice.ucdavis.edu/node/4875) to obtain additional information and to download survey materials.
We are seeking additional participants to survey both historical colony locations as well as to survey in appropriate regions for new, previously undocumented colony locations and to estimate the number of birds at occupied sites. No prior experience is necessary and any level of commitment, big or small, is welcome to help to make this year's survey as complete as possible.
To volunteer for this year's statewide survey, contact Keiller Kyle at kkyle (at) audubon (dot) org.
A new report, "Recent History and Current Status of the Tricolored Blackbird in Southern California", prepared by the Western Riverside County Multiple Species Habitat Conservation Plan Biological Monitoring Program, has just been released. The report reviews the annual abundance of breeding tricolors in southern California since 1994 and provides an update on the status of the species.
The report documents the alarming decline of tricolor abundance in southern California since 1997 and reveals the importance of Riverside County to tricolors in the entire southern California region.
The report provides suggestions for management actions that may help to reverse the decline and enhance the prospects for the persistence of the species in southern California.
In 2006, fewer than 30 cattle egrets (Bubulcus ibis) were observed for the first time preying upon the contents of nests of tricolored blackbirds in a single colony in Tulare County. During March and April, 2010, three large (> 30,000 birds each) tricolor colonies in Tulare County suffered near-total productivity losses to predation by cattle egrets, where up to 220 cattle egrets were consistently seen in tricolor colonies.
Thus, in only four years the cattle egret has become perhaps the tricolor's most serious threat to survival, and if the scope of cattle egret predation should increase beyond Tulare County (so recently a population source but now a population sink) , the tricolor could be in serious jeopardy. Cattle egrets are common, and increasing in abundance, throughout much of the Central Valley, but to date they have been documented to prey upon tricolors only in Tulare County.
Tricolored blackbirds are being banded as part of a statewide effort to identify and document movement patterns and fidelity to breeding colonies. The banding of tricolors began in 2007 and has continued annually, with over 47,800 tricolors banded by autumn, 2011. Thus far, all birds have been banded during the breeding season at sites adjacent to breeding colonies.
The recapture of banded birds has demonstrated strong fidelity to breeding sites and a high degree of colony cohesion, with birds breeding together at one location tending to move as a group to breed together again at a different location. Previously-banded birds tend to be recaptured in groups, a phenomenon that requires an explanation while suggesting that birds are not only breeding site faithful, but that breeding birds may recreate spatial relationships established in one location at subsequent breeding colonies.
The Los Angeles County Department of Public Works provided a letter to the West Valley County Water District Board of Directors, informing the District that the County does not believe the existing Drought Ordinance applies to Holiday Lake. Therefore, the County of Los Angeles does not intend to take any action against the District to prevent the operation of the recreational facilities at Holiday Lake as an enforcement of the Ordinance. In a recent Board meeting, the District, after much debate, decided not to adopt the Ordinance. This decision supersedes the order to cease pumping made by the Board President last January, thus allowing water to again flow into Holiday Lake. With the return of water deliveries, it is hoped that the largest tricolored blackbird colony in Los Angeles County in 2008 will be active this year.
An article in the Antelope Valley Press dated March 11th, 2009 illustrates the interaction between water conservation policy and tricolored blackbird breeding and describes the situation at Holiday Lake in northern Los Angeles County, where water deliveries had been terminated, threatening the largest breeding colony of tricolors in Los Angeles County in 2008 (according to the 2008 Statewide Survey).
Subsequent actions by the Los Angeles County Department of Public Works have restored water deliveries to Holiday Lake and it is hoped that tricolors will breed here again this year.