Back to Work for Drakes

Male Hooded Merganser displays: ritualized drinking (left) and crest raising (right)

It's late October, and our adult male Hooded Mergansers have all molted back into their handsome breeding plumage. These fancy feathers come out for a compelling reason - courtship has begun, even though nesting is still 6-7 months away.

Hooded Mergansers are seasonally monogamous. The pairs only stay together for one breeding season, and the bond dissolves when the females start incubating eggs. The males then molt into a drab, "basic" plumage and lay low for the rest of summer. About the time the juveniles are grown and the adult females are released from their motherhood duties, the adult males molt back into their fancy feathers and the whole thing starts again.

By late summer we start seeing antagonistic displays, as males grapple among themselves, and courtship displays where males vie to impress females. If he's successful, she pairs off with him and they spend the winter together before nesting next year.

The male Hoodeds do almost all of the courting while the females mostly just observe. There are a dozen or more ritualized, exaggerated movements, including: head shake, head pump, upward stretch, crest raising and crest depressed towards the female.

But my favorite courtship behavior is a serious head throw with croaking - as in frog sounds. The male starts with a crest raise, fanning his white head patch and pointing his black brow feathers forward into a point. With gusto, he whips his head back and releases a low-pitch croak that sounds exactly like a summer-time frog (listen here). Others have photographed this but, unfortunately, I've never been allowed. I've tried blinds and remote cameras, but the males always move away from the slightest shutter sound.

My second-favorite Hooded Merganser behavior is ritualized drinking. An excited bird dips its bill in the water and flings it skyward. Males perform this move with their crest depressed, and both sexes do this near each other as a pre-copulation behavior. Once pairs form, copulation can occur during fall and winter, before spring's longer days alter duck hormones to allow for fertilization and egg-laying.

Duck copulations in October are a part of pair bonding, and copulations through winter and spring are for pair maintenance. This usually involves two more behaviors. Females incite mating with a soft "gack" call while head bobbing, and steaming is the male's exaggerated swim away from her after mating.

What makes this all fun for me is to anthromorphize, watching the earnest ducks and comparing them to the odd behaviors seen in flocks of young humans who are still years away from raising a family. It's about the only way I can understand some exaggerated human behaviors.

Male Hooded Merganser performs a ritualized and exaggerated drinking motion

Pecking Order

Adult Loon near the lily pads

No young Loons this year, here at the end of the road. Our resident pair of Loons hatched two chicks, but one only lasted one week and the other lasted two. So the adults have been free-floating this summer, appearing and disappearing at will, and even tolerating a few visiting Loons from time to time.

Because they aren't tied down to the marsh this year, which they use as a nursery to raise their young, the adult Loons have been spending more time on our side of the lake as summer wears down. And having resident Loons with time on their hands is causing strife in the neighborhood.

Juvenile Hooded Merganser

Many of the neighborhood ducks hang out on this side of the lake specifically to avoid the bad-ass Loons. Twice as big as our largest ducks, the Loons are territorial while nesting and chase other Loons off the lake. But now that they're not nesting or raising young, the Loons have turned their attention to the ducks, especially the little diving ducks that eat the same food.

The juvenile Hooded Mergansers feed in a narrow opening between our shoreline and the lily pad thicket. Feeding quietly, or resting on a log, they'll suddenly explode out of the water and rush to shore, facing towards the lily pads. This is our cue to search for the hidden Loon.

Eventually a skulking Loon surfaces like a submarine just beyond the lily pads, or even in the middle of the thicket. Earlier this week, our favorite neighbors saw a Loon apparently grab a Merganser from underwater, as the Hoody exploded towards shore and the Loon suddenly appeared where the duck had been.

We don't attribute the ability to rationalize to birds, and this is just considered normal behavior. The Loons aren't mean or angry or frustrated, they're just doing what their hard-wired brains tell them to do. And the Mergansers who survive these encounters will be the ones to pass along their genes for vigilant behavior. Just the natural pecking order here at the end of the road.

Real Ducks Don't Wear Swim Goggles

Hooded Mergansers have special adaptations for sharp vision above and below water 

Ever opened your eyes underwater? Of course you have. Doesn't work so well for us terrestrial types, does it? But what about aquatic animals like fish or even semi-aquatic ducks? How can they see underwater without wearing goggles?

Can I clear up the fuzziness in a few words? Probably not.

Land-lubber eye diagram (courtesy NEI)

Modern animal eyes are quite a marvel. The whole complicated assembly evolved to serve one purpose - bending light. A combination of eye parts redirects light waves to converge on the fovea (Latin for "pit"), a small spot on the inner light-sensitive layer, the retina, lining the back wall. Half of all the optic nerves reporting from the eye to the brain originate from this pit, which has the highest density of color-sensitive cones and is responsible for sharp vision.

For the most part, our modern eyes use just two parts to bend light into focus, the cornea and lens. The cornea is that curved outer part that you rub when sleepy. Behind the corneal cover and iris opening (the pupil), sits a clear and flexible lens that gets mushed about by tiny muscles, changing shape to bend light into different magnifications. Changing the eye's magnification power is just another way of saying that you are changing your focus between near and far.

In land animals, our curved cornea accounts for a whopping two-thirds of the eye's ability to focus light (called "accommodation"). It works mostly because light changes speed when moving through different mediums, faster through air in front of the cornea but slower through our liquid eyeball. This bends the light rays in towards the lens.

For us mere humans, our eyes working above water have about 40 diopters of optical power. (One diopter means the lens can focus at 1 meter, or 39 inches. Two diopters focuses at one-half a meter, and so on. More diopters equals more magnification power.) A young person can reshape their lenses to gain an additional 20 diopters. But this drops to 10 extra diopters by age 25 and fades to only about 1 extra diopter by age 50. Thus, the reading glasses I'm currently wearing and the extra diopters I keep adding to my camera's viewfinder.

Fine. But what about underwater?

Our land-lubber eyes are mostly filled with liquid, so when we open our eyes in water, the light is moving from water into a similar liquid (with a similar refraction rate), and this effectively removes our corneas from the equation. Limited to just the lens, our land eyes can only manage to focus incoming light behind our pits. The result is fuzzy fish - and perhaps the inspiration for those fur-bearing trout in Iceberg Lake.

So how do aquatic animals see? Well, it depends. We used to think that animals with clear nictitating membranes (a retractable, lubricating outer layer) used them like goggles whenever underwater. That theory was quickly dispatched, but several different solutions would eventually come to light.

Westslope cutthroat trout

Fish have corneas to protect and contain their eyes, but these don't really help with clear vision. However, most fish have convex (bulging outward), almost round, lenses with an internal density gradient. This gradient allows fish eyes to bend light inside the lens itself instead of just at the lens surface.

But some fish also spend parts of their lives out of water. Some of these semi-terrestrial fish have an extra chamber behind the cornea, which allows them to still see well when the focal point is projected beyond the primary cornea, when these fish moves between air and water. The famous four-eyed fish has hourglass-shaped pupils, with the top half of the retinea adapted to seeing in air and the lower half adapted for seeing in water - It can see above and below at the same time! Unfortunately, the nearest of these cool species lives in South America.

Other fish and some birds, like penguins and albatross, have a flattened cornea, so the small amount of optical power lost by the cornea underwater is still within the focusing ability of their lenses. Other diving birds that chase fish underwater arrived at yet another answer. Some of the duck species here at the lake can see clearly in air (flight, landing, predator avoidance, etc.) and also underwater when in pursuit of pursue fish. Goldeneyes and Hooded Mergansers fall into this fish-eater category.

Remember those tiny muscles that reshape the lenses? Well, they're not so tiny in fish-eating bird species. These birds use their comparatively-larger eye muscles to squeeze their lenses into the opening (the pupil) formed by the colorful, constricted iris. By squeezing lens against iris, the lens distorts enough to become close-focusing. With these super-deformable lenses, diving ducks can immediately compensate for corneas - so valuable above water - that become useless underwater.

So diving ducks have sharp vision above and below water? Well, yes and no. According to one research team, these ducks don't switch over to their "underwater eyes" until they get close to something of interest (usually a fish), within about a bill's length away.

Like me, diving ducks appear to have brief flashes of clarity sandwiched between longer periods of fuzziness. Otherwise, I could have cleared this up in half as many words.

Mergansers in the 'Hood

Wind-blown male Hooded Merganser

A "Lake Wind Advisory" blew in this afternoon, here at the end of the road. After enduring several hours of sustained winds of 20-25 mph, I finally gave up and moved my woodworking project indoors. Later on we pulled a small boat out of the water for two young men who had given up on paddling back to where they started - more beer than brawn aboard that vessel.

Today's wind advisory was below a "Gale Warning" (39-54 mph) and a "Small Craft Warning" (26-38 mph). But it was still windy enough for some of the smaller "craft" to haul out on shore. Or in this case, our dock.

Two of our lake's four pairs of Hooded Mergansers (Lophodytes cucullatus) tried to sleep through the storm from the safety of our old dock. The oldest and most handsome male, however, had to keep shaking his head feathers back into place every 10-20 seconds. His body was facing the wind, but his head was turned downwind in normal sleep position with his beak on his back. The other three birds slept just fine, but this guy didn't seem to get much rest at all.

Only one of the four females has young this summer, nine little fluff balls that first appeared just a few days ago. Still, Hooded Mergansers are one of the few duck species that appear to be increasing their numbers throughout most of their U.S. range (39 of 49 states), including Montana. Come fall, most of our mergansers will migrate westward to the coast. But a few will stick around and endure our winter storm warnings - wind and all.

Hooded Merganser pair on a calm day earlier this week

Hooded Merganser vs. Crayfish

A male Hooded Merganser turns a live crayfish around in its beak before swallowing it whole. They'll often break the pinchers off first, but not this time. Sorta' makes me wonder what that feels like in one's stomach...

Hooded Mergansers

The Wood Ducks ("Woodies") have left our little lake here at the end of the road. Nowadays, it's the male Hooded Mergansers ("Hoodies") who are looking downright studly again.

Male Hooded Mergansers (c) John Ashley

After spending much of the summer in a female-like basic plumage, the male Hoodies have moulted back into their handsome breeding plumage. It makes for a more impressive courting display, when they throw their heads back and make a creaking, sort of frog-like call. The males have been performing this display for each other, as well as in front of the females. For their part, the females seem to play coy, not showing any apparent reaction to these creaking males amongst them. Sorta' reminds me of college days for some reason.