The Love of Hooded Mergansers

As a kid growing up on the Canadian prairies, I didn’t have too much birding to do in the winter (I mean crows, magpies, and house sparrows only get you so far—although the downy woodpeckers and chickadees were great.)

So I learned a lot of my birding skills from library books. One of the birds I most wanted to see in real life was the hooded merganser. I mean, why wouldn’t you? Such a dramatic creature, with that bold yellow eye, the elongated beak, and of course that amazing black and white crested head.

I don’t think I saw one in the wild until my thirties. Now that I live on the west coast, the arrival of the “hoodies” is an annual phenomenon.

Meet the mergansers

Mergansers are a group of fish-eating ducks. In British English they’re called goosanders, which kind of sounds like a nursery rhyme character to me. But the hooded merganser is a uniquely North American bird; it’s the only merganser endemic to this continent.

People who study merganser systematics (the interrelationships among birds) tell us that this species is sort of halfway between mergansers and goldeneyes, which makes total sense if you look at them—and watch their mating behaviour. They can really put on a show.

That crest, though.

A lot of birds express themselves through crests on their heads—even some birds that don’t really have crests. Watch crows interacting, for example, and you’ll see “crests” (the feathers on their foreheads. Wait, do birds have foreheads?) raised and lowered constantly. They indicate who’s aggressive, who’s excited, who’s dominant, who’s looking for trouble… All of this is loud and clear to other crows, even though there really isn’t much crest there as far as you or I can see.

At the other end of the spectrum are the birds whose crests are veritable public address systems. Cockatoos, for example. Kinglets. Jays. And, of course, the hooded merganser. What a crest! They keep it slicked down when fully relaxed, and they compress that beautiful big crest down to nothing just before they dive. It must be quite a drag in the water.

Madly mating mergies

Where the crest really comes into play is in mating season. When a pair of hoodies is declaring interest in each other, they do it with their heads, and man, that crest is busy. Biologists who study merganser behaviour have it all catalogued out. There’s crest-raising, there’s head-shaking, there’s the old turn-the-back-of-the-head, and of course you’ve got your head-pumping, your upward stretch, not to mention the upward stretch with wing flap… and last but not least, ritualized drinking. I kind of relate to that last one.

It all sounds bewildering but it makes for some wonderful birdwatching and bird photography. Hooded mergansers have to be one of the most photogenic birds in the pond.

Until, of course, they dive and disappear.

Mergansers are diving ducks (unlike your mallards and wigeons, say, that only dabble on the surface.) They get around beautifully underwater, propelling themselves nimbly with their legs alone (some diving birds ‘flap’ underwater—but not these guys.)

They eat fish, amphibians, and invertebrates. Whatever critters they can find down there, really, but in areas where crayfish are plentiful, hooded mergansers chow down on a lot of them. And to do that underwater hunting, they not only use their swimming agility but their excellent underwater vision, too.

Bird’s eye view

Did you ever think about what a challenge it must be for birds to see well underwater? Think about it: you and I have to put on a face mask or goggles if we want to see anything when we swim. But a duck’s eye has to function underwater, above the water, and even in the air when zooming along at high speed. Bird eyes are amazing.

It helps that they, like other birds have an eyelid that we don’t have. It’s called the nictitating membrane, and it slides over the eye whenever it might need some protection from the elements—particularly in flight and in the water. It’s a bit of protection if that crayfish wants to fight back, for example. Cats have those membranes, too. I’m not sure why people missed out on nictitating membranes—they’d sure be useful.

Seeing the watery world

Anyway, in addition to that membrane, hoodies have another underwater superpower: the lens of their eye can accommodate the extreme changes required to see well underwater. Think about it: as soon as you open your eyes in the water (and I’m not necessarily recommending that you do), you’ll notice blurry vision. Water refracts light differently than air, and your corneas are definitely optimized for life on the land.

Now, when presented with any focussing challenge, people like you and me try to accommodate by changing the shape of the lens in our eye. You might not know you’re doing it, but you do it a lot (and you won’t know how much you depend on it until you hit about 45 years of age and you start losing that ability. Hello, reading glasses.)

But mergansers (and some other diving animals) are able to really flex that lens. In fact, they push the lens of their eye way forward right into the pupil, and suddenly that underwater world (with its fast-moving fishy prey) is in clear focus.

Nesting in trees

I wonder what it must be like to be so at home in different worlds. Hooded mergansers are powerful fliers and long-distance migrants; they are completely relaxed bobbing on the water, and agile under the surface. But there’s more: they nest in tree cavities at the water’s edge. This duck, this bird perfectly adapted to swimming, suddenly has to fly at high speed straight toward a tree trunk; put on the brakes in a hurry; grab the edge of that cavity with its webbed toes; and get through that hole before falling to the ground in a heap.

And they’re really good at it! Goldeneyes have been known to crash and miss—hooded mergansers are pros. And they’re not just flying into their own nest cavities, either—they’re seeking out others. Female hooded mergansers, like so many other ducks, practice egg dumping. They lay extra eggs in the cavities of wood ducks and others, as a kind of insurance policy.

Hooded merganser eggs are thick-shelled, and more spherical than other ducks’. Why? Nobody really knows, but have a look at what this biologist found: they might just be more resistant to predation.

Like all ducklings, mergansers have turn-key babies. That is to say, ducklings can swim and hunt and react to danger pretty much as soon as they’re hatched, unlike sparrows and robins which are helpless and icky-looking.

Wishing them a long and fishy life

Those fluffy babies can hope to live up to ten years if all goes well for them. Of course, they face dangers of all kinds: falcons, eagles, lynxes, and human hunters, too (although they’re not nearly as popular a hunting duck as they were earlier in the 20th century.) They’re not an endangered species, fortunately—there are probably somewhere in the range of 300-400,000 in the world, spread into eastern and western populations.

As long as we can maintain healthy wetlands and lakes, hooded mergansers should be with us for a while. I hope so. I have a lot of photos to take of them yet.

Let me brighten your Friday.

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