Hooded mergansers migrate through southeastern Idaho

Hoping to locate a pair of Hooded mergansers that had spent all winter in the Burton area near Rexburg, I was surprised to locate not only the couple, but 14 of them last week. All of them were busy catching crayfish and small minnows; but most of their busyness was the males chasing other males away from their significant others.

The boys outnumbered the girls so while the boys were fighting, the girls stopped their eating and watched the boys battle just a few feet from the violence. Several times after that battle, the girl would dive, then swim a few feet past the apparent winner and swim or fly off with the loser.

Little did I know that the pair had become a couple during the middle of the winter somewhere in the Pacific coastal states. The loser continued to be her knight and her protector while the winner looked for another couple to harass.

They get their name from the crests that both genders display during breeding season. The males sport a rounded white crest edged in black while the females have a brown one that blends in well with her body color.

I watched that flock of hoodies for three days and when I showed up the fourth day all but a committed couple had moved on. I did find five males and three females cavorting at the Warm Slough about ten miles away. I don’t know if they were from the same group or another group migrating through and there were also four at Market Lake the same day.

Mergansers are the only ducks that live almost exclusively on fish and/or crayfish. They will swim with their head just under the surface of the water trying to spot prey, they then will dive to capture their meal. They are blessed to have a second transparent eyelid called a “nictitating membrane” to protect the eyes during dives as they hunt by sight.

The hoodies love crayfish and once they have captured one, they will swim to the surface and violently beat the crayfish on the surface to break off the pinchers before eating the delicacy. They have strong enough muscles in the stomach to digest this crusty cuisine.

These small waterfowl are cavity nesters and use old nests created by woodpeckers, squirrels, wood ducks and woodpeckers. Nest boxes with an opening of three inches high and four inches wide placed near water and wooded areas will also attract these birds. They like their nests from 10 to 50 feet above the ground.

Once the females start setting on the eggs, the male abandons her. After about 31 days, all of the ducklings hatch and after 24 hours after hatching, the female gets on the ground below the nest and calls to them. In a very short time, all the ducklings jump from the nest to the ground and is led to the nearest water where they feed themselves.

An odd thing about the hoodies nesting is that other females may also lay eggs in another female’s nest. This is called “brood parasitism.” Each female will lay about 12 eggs, but nests have been found to have over 40 eggs in them.

“We have a few hoodies nest in the Upper Snake River Region, but it is only a few,” explained Matt Proett, an Idaho Fish and Game wildlife biologist. “They are most likely to be found along the Henrys Fork from Ashton to Roberts, area canals and the Warm Slough near Rexburg.”

The largest concentration of hoodies that I have found during their migration to nest in northern Canada has been on Camas Creek where it runs into Mud Lake. As the water users start filling Mud Lake with well water, hoodies battle with their migrating cousins, the Red-breasted mergansers of the dead fish in Camas Creek.

I felt extremely lucky to have found these migrating beauties near my home. Hopefully the couple that is left will have a successful nesting season and we will continue to see more hoodies locally in the future.

By the way, Brian Wehausen, manager of the Camas National Wildlife Refuge, told me that due to repairing and improving some of the ponds and canals this summer, the refuge will not have water this summer. More on that at a later date.