A bumblebee species is disappearing in Canada and researchers say they\'ve been unable to determine what turned it from a common sight to an endangered species. A rusty-patched bumblebee, once of the most common bees in southern Ontario and Quebec, is the first bee in North America to be officially declared an endangered species, Postmedia News reported Sunday. The species, Bombus affinis, with a distinct orange patch on its abdomen, may be the victim of climate change, pesticides, habitat loss and pathogens, but researchers have been unable to pinpoint a cause. The drastic decline had gone mostly unseen until Sheila Colla, a doctoral student at York University, first noticed it. \"It shows we are really not paying attention, which is kind of scary,\" she said. Bees are key ecological players and pollinate crops that produce one-third of the human food supply. They deserve more attention and study, in part because they are very sensitive environmental indicators, York biologist Laurence Packer said. \"They\'re like the canary in the coal mine,\" Packer said, and the disappearance of a common species such as the rusty-patched bumblebee is \"a warning signal that things are going wrong in the great outdoors.\"