This great blue heron moved on from Six Mile Lake in northern Dickinson County after a brief spring stay. (Iron Mountain Daily News photo)

IRON MOUNTAIN — The spring migration brought an unexpected treat to Six Mile Lake this month: a great blue heron in near-full breeding plumage.

While great blue herons aren’t unusual at the lake, most that I see are later in the year and dull, more gray than blue, with blurred markings.

This one was in “impress a prospective mate” mode. Its well-defined black eye stripes against a white background tapered to thin feathers, called occipital plumes, that trailed behind its head. A vivid blue patch of skin framed its yellow eyes and contrasted with the deep orange-yellow bill. It could have been male or female, as unlike many songbirds both sexes take on distinctive plumage for courtship.

The only touch it seemed to lack — at least for now — was the long, shaggy plumes on back and neck that herons can sport during nesting season.

Still, the sharp-dressed look hinted this bird wouldn’t linger long, even if the fishing was good. Great blue herons normally nest in colonies called rookeries, in large stick nests in trees near both freshwater and saltwater habitats. Those rookeries have been documented in other parts of the Upper Peninsula, such as Isle Royale, but not at Six Mile Lake.

As expected, the heron moved on after a couple of days.

The great blue heron is the largest of its kind in North America, and globally ranks only behind two other herons in size — the well-named goliath of sub-Sahara Africa, about twice as large as the great blue, and the critically endangered white-bellied heron, now limited to portions of the Himalayas, India and a few other southeastern Asia countries.

Thankfully, our great blue heron appears to be thriving. It is found across North America as far north as Alaska and as far south as Venezuela and Colombia in South America.

In the U.S., great blue heron numbers increased between 1966 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 700,000.

Unlike greater sandhill cranes that will eat plant tubers and seeds, herons are strictly carnivores, though their tastes extend to whatever they can catch with a lightning strike from that snake-like neck. Their diet includes not just fish and amphibians but reptiles, small mammals, insects and even other birds. I’ve seen photos of them snapping up chipmunks, voles and ducklings.

If this one does find its way to a nesting colony and a mate, herons in this region average about four eggs that hatch in late May. The ones that do show up at Six Mile Lake by late summer often appear to be juveniles hatched that year.