The report from the British Trust for Ornithology contradicts the widely held view that gray squirrels have significantly depleted some woodland bird species because they eat eggs and kill and eat baby birds.
Researchers studied the gray squirrel's impact on 38 bird species throughout Britain and found the squirrels suppressed bird populations in some local areas, but did not cause widespread harm or lasting damage.
Blackbirds and collared doves were found to have thrived despite nest attacks from invasive gray squirrels and native red squirrels, the researchers said in a recent issue of the Journal of Ornithology.
Britain has more than 2 million gray squirrels and about 160,000 red squirrels. Gray squirrels have proven harmful to red squirrel populations because the grays spread a form of pustular dermatitis that does not affect grays, but can kill red squirrels within a week of infection, the BBC reported Friday.