Ospreys with attitude

🕔May 22, 2008

Having found where the ospreys were nesting, during the previous summer’s helicopter survey of the Nechako Reservoir (see Nest spotting, page 10), the next question was: Why were they there, and what were they doing?
Jim Williamson and I went to find out. We picked nine active osprey nests, which we imaginatively called A, B, C etc. and kept dawn-to-dusk watches on each adult pair for two days in each month during the breeding season.
We soon found out that, although ospreys en masse look like just a whole bunch of birds, individual ospreys are—well—individual.
Our first pair (nest ‘A’—therefore ‘Alf’ and ‘Mrs. Alf’) had had to reclaim their nest from a pair of Canada geese who, having returned from the south before the ospreys, had taken it over and were busily turning it into a goose nest. (Geese like platform nests too, and hey—here was a nice one already built!)
Although the intruding geese had been driven off by Alf and his mate, they hadn’t gone very far. In fact, they’d made a new nest on the lakeshore only 20 metres away. Mrs. Alf never forgave them for this territorial infringement: she truly hated those geese. Every time they flew by (which was about a dozen times a day—they were raising a family too), she set up a shrieking and a screeching that could have wakened the dead. It didn’t seem to bother the geese at all, though; nor did it bother the neighbouring osprey pair (Bill and Mrs. Bill), who would cast a tolerant glance in her direction and then carry on with their daily round. It did, however, bother Alf, because once Mrs. Alf had finished berating the bothersome geese, she’d start in on him.
Female ospreys don’t fish during the breeding season; the male fishes for his mate and his family and brings his catch to the nest for them. She leaves off brooding the eggs or chicks just long enough to get a bite to eat, then settles back on the nest. So Mrs. Alf was completely dependent on her mate for her daily meals and, in her opinion, he was falling sadly short of the ideal. He’d be sitting on a nearby snag, watching the world go by, and she’d start nagging him—first a few disgruntled squawks that sounded for all the world like, “I don’t know what you think you’re doing, sitting there like you’ve got nothing to do.” Then she’d get louder, more raucous and more agitated until—well, you could almost see him heaving a sigh and saying, “Oh alright then!”—and he’d take off and fly along the shore, presumably to look for a fish.
What Mrs. Alf didn’t see was that actually he only flew a few hundred metres along the shoreline, around a point and into a little bay where she couldn’t see him. There he’d settle onto another snag and fall back into his customary reverie in blissful peace and quiet. Sometimes he’d catch a fish, and sometimes (not always) he’d bring it back for her. But harmony was restored, so that was alright.
Cyril, the “C” male, avoided domestic strife by never fishing in the reservoir at all. Every morning at about 7:30 am he’d head off across the lake and didn’t come back until late afternoon. We never did find out for sure where he went, but he always flew in the same direction, towards a group of four small lakes about five kilometres north of the reservoir, and he always brought a fish back with him. Maybe it was worth the trek.
Curiously, Cyril’s neighbour Diarmuid (we were getting quite imaginative with names by then) hardly ever went more than a few hundred metres from his nest, and he was by far the most prolific provider, often catching eight or ten small fish in a day. (One or two is more usual.) Diarmuid was the perfect practitioner of perch fishing. Never mind the dramatic osprey fishing dive, plunging from a great height with talons extended to snatch the unwary prey from the water; Diarmuid sat on a branch until a fish swam underneath, and then dropped on it like a stone. It worked, and it’s much less effort than flight hunting!
Perch fishing may be why there are so many ospreys on the reservoir, where there are so many trees and branches right over the water: flight hunting is a strenuous way of getting a meal, and the return may not be worth the energy. But then why did Cyril and Diarmuid, whose nests were barely 200 metres apart, use such very different fishing techniques? And does it matter, in the end? Both fledged two chicks—although one of Diarmuid’s was the only chick we ever saw catch a fish independently.
Adults continue to feed their young until they leave in September. The young birds seem to practice fishing dives (or perhaps they were accidents; newly-fledged birds don’t fly very well, and it takes a while to master skills like landing)—but they never seemed to catch anything. Possibly ‘Little Diarmiud’ fell off his branch and just happened to land on a fish—but we like to think that we witnessed his first step into self-sufficiency.
We watched another young bird, very likely on his first flight, crash-land unceremoniously into someone else’s nest. The owners naturally took umbrage at this and dive-bombed him, chasing him off. The fledgling floundered through the air and landed like a sack of potatoes on a short, broken-off snag, getting his foot stuck in a crack.
We witnessed this and went charging to the rescue. By the time we got there poor ‘Achilles’ was hanging by his heel, upside-down and helpless, over the water. We considered our options, quickly agreeing that we should keep our hands out of reach of those talons and that wickedly hooked beak! By using a boat paddle we managed to free his foot—whereupon he promptly fell into the lake. We delicately fished him out of the water and parked him on a more secure perch to contemplate his errors and recover from the ordeal. Hopefully he learned from his experience and is now one of the busy parent birds still crowding the snags of the reservoir.