The Scourge of Blackflies

As this searing photo by Linda Grenzer demonstrates, blackflies are making incubation miserable for loon pairs this spring. Actually, this guy — a 16 year-old male from Muskellunge Lake — is hanging tough despite dozens of the remorseless bloodsuckers. Where blackflies infestations are worse still, such as the hundreds we have seen swarming around nests on Bobcat and Upper Kaubashine lakes, loons abandon their nesting attempts altogether. Based on visits to dozens of lakes this spring, it seems that about 70% of all loon pairs that have started



nesting have been unable to incubate owing to blackflies. This is much the highest rate of blackfly-induced abandonment that I have seen in 22 years of loon study. (32% was the worst rate before this year.) These dipterans are such a nuisance that they even cause loons to change their daily activities. Normal adults spend lots of time oiling their features, preening and resting, but those terrorized by the tiny flying demons spend virtually the entire day diving, surfacing to take a breath and shake their head free of blackflies, then diving again. Luckily, most pairs that abandoned their nests due to blackflies did so within the first week of incubation. Thus, they still have plenty of time to renest, which most will do soon.

While loons are no doubt the most serious victims of blackflies, the tireless arthropods impact field observers as well. You see, preening and resting are the two activities of loons that make it easiest to ID individuals. Since loons have reduced or eliminated preening and resting from their activities and, instead, begun to dive incessantly to avoid flies, we have a devil of a time getting close enough to individuals to identify them from their colored leg bands. (Loons have even shortened the resting time between dives to reduce their exposure to blackflies.) So, we too look forward to the end of a brutal year of blackflies.