Last week was a tense one. Dozens of pairs had laid one or two eggs, but black flies descended on them, making incubation impossible for most. Of the fifteen or so pairs with nests last week, only two incubated at all, and one of these pairs sat only during the first twenty minutes of our observations. (The other was Linda Grenzer’s notorious overachievers, Clune and Honey.) All other pairs spent their time in the general vicinity of the nest — but diving frantically, shaking and tossing their heads, even snapping their bills fruitlessly at the relentless biting insects.

Already frazzled by the grading of 131 all-essay final exams, calculation of final grades, and strident pleas of disappointed students — I fielded another while writing this post — I feared another dreadful year of nest abandonments, like 2017.

What a difference a week makes! While not altogether gone, the flies are dwindling rapidly. Breeders that could only view their eggs from afar 7 days ago are back on them. I caught the male in the photo — from Two Sisters Lake-Far East Territory — about to hop cheerfully onto his nest, after an incubation switch. He and his unbanded mate still have 27 days of incubation remaining. But, like all of our focal pairs, they have overcome the first major hurdle.