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.
How to reduce the threat of predation by cattle egrets on the eggs and nestlings of tricolors will be actively debated, but doing nothing is probably not an option.
If you see cattle egrets in a tricolor colony, please report the observation to the Portal.