‘California’s blackbird’ in sharp decline
Numbers of Tricolored Blackbirds in California have crashed by 44 per cent since 2011, a study published in June has revealed. This comes on top of a 34 per cent decrease in 2011 from 2008.
The results show that there are about 145,000 of these colonial songbirds living in California, down from some 260,000 in 2011 and 400,000 in 2008. This is despite the 2014 survey covering a larger number of breeding populations. During the three-day study, 143 volunteers organised by 38 co-ordinators surveyed 801 sites – up from 361 sites surveyed in 2008 – across 41 counties. Survey participants entered records of their observations into the Tricolored Blackbird Portal, developed and hosted by UC Davis.
Sadly mirroring the loss of Passenger Pigeon, it is thought that the birds numbered in the millions in the 1930s, and if efforts to protect Tricolors fail this could be another species consigned to extinction.
The survey was co-ordinated by UC Davis staff researcher Robert Meese, who has studied Tricolors for the past decade. He commented: “It’s California’s blackbird. If we as Californians don’t care about the species, we can’t rely on any other state to come in and bail us out. It’s our responsibility because it’s our bird.”
Reasons for the decline
The survey data show that the bird is declining most rapidly in California’s ‘dairy belt’, in areas where triticale – a wheat-rye hybrid feedstock for dairy cattle – is grown. For decades, Tricolors have established large nesting colonies in triticale. When these fields are harvested before young birds have fledged, thousands of eggs and nestlings are lost. If the crop harvest is delayed to accommodate the nesting birds in the fields, the triticale loses the nutritional value needed to feed the cattle. Efforts to compensate farmers for waiting to harvest until after the breeding season have resulted in protection of many breeding colonies, but losses to harvest continue.
Perhaps the biggest problem, however, is the chronic, low reproductive success of most colonies since 2007. Research by Meese has shown that the birds produce few offspring unless insect populations surrounding their breeding colonies are high. “If they do not have enough insects in their diet, they simply cannot form eggs,” Meese said.
Meese is trying to convince growers to give up pesticides. “The blackbirds could act as a natural insecticide,” he commented.