The double-crested cormorant gets a bad rap. But give this big, prehistoric-looking bird some props: the species’ numbers have exploded since the 1970s, after they suffered at the hands of DDT. Just like eagles, cormorants would eat fish contaminated by the pesticide (and produced eggs with too-thin shells as a result). In 1950, there were only 900 breeding pairs in the Great Lakes. By 2000, that number had jumped to 115,000.
What do cormorants eat?
Some anglers aren’t huge fans of this bird, which, fair enough: it does spend much of its time catching fish. Flocks of cormorants will fly dozens of kilometres from their home base to forage. They soar in tight formations then dive below the surface of the water to catch more than 250 species of fish, including small fare such as minnows and yellow perch, plus invasive species including round goby and rainbow smelt. For the record, anglers, most research shows that sport fish only make up a small percentage of a cormorant’s diet.
Cormorants are excellent swimmers—at least, they are when they’re going after food. This bird has a cool fishing technique: it chases after fish underwater, propelling itself with its webbed feet. (Other bird species that swim underwater, like the Cassin’s auklet, use their wings like fins to “fly” as they pursue prey.) Cormorants have hook-tipped beaks for a reason. They use the hook to snag their dinner. Sometimes they catch crayfish. When they do, they repeatedly bash the crustacean against the surface of the lake until its legs fall off, then flip it into the air to catch and swallow it head-first. Show off.
Why do cormorants ‘pose’?
When a cormorant isn’t fishing, it’s just hanging out. This bird spends at least half of its day resting (hey, sounds like a cottager!). Ever spot one standing on a bare, windy rock or branch—or on your dock—with its wings outstretched? It’s trying to dry out. Cormorants have less preen oil (the stuff that helps ducks shed water) than other birds, so their feathers are soaked after a morning of fishing. Experts believe this difference is what actually helps cormorants hunt underwater more effectively.