Common Loons, often attacked by black flies, can be driven from nests for this reason, abandoning eggs.


A study in Canada has shown that the birds will renest more often than if they lost eggs to predators. 


That is good news because the flies are common in early summer in the heart of Minnesota loon country (see photo below).


The research was undertaken last year in Canada, results published in the ornithological journal “The Auk.” A link to the article was provided in the current issue of the online newsletter “Bird Studies Canada,” a source of interesting and important articles about birds.


Perhaps you remember the reports of nest abandonment by nesting  Whooping Cranes at and near Necedah National Wildlife refuge on central Wisconsin. The flies were a serious impediment to efforts at building an eastern flock to increase Whooping Crane population.


The flies, hatching from fast-moving water, have a life of no more than a few weeks, but can do much damage to nesting birds in that time. The flies seek animal blood (yours and mine as well as that of birds). They attack the vulnerable non-feathered areas around a bird’s eyes. The crusting blood from the fly wounds can blind a bird.


Here is the link to the article. The summary of the article explains the problem, the study, and its conclusions.


Common Loons respond adaptively to a black fly that reduces nesting success


The journal itself, with archives of previous articles, is online at The journal can be a frequent source of studies relative to Minnesota birds.

Black flies attacking a Common Loon (photo from an undocumented source)