Mike Hamilton is a birdman. The Sammamish resident and retired Boeing employee photographs birds pretty much every day. But the herons are his favorite. Specifically the great blue herons in Renton’s Black River Riparian Forest. Hamilton spends every Wednesday afternoon with friends in the city-owned, 93-acre forest just off Oakesdale Avenue Southwest.

“We bring cheese and crackers and watch the herons,” Hamilton says.

There’s plenty of herons to watch this time of year.

Called Coastal herons, Renton’s long-legged birds are a unique subspecies found only in the Puget Sound area and in a valley near Vancouver, B.C.

The elegant blue birds began returning to the forest in mid-March. They returned to their forest homes — 80 or so nests topping a cluster of slender birch trees. Just across from the trees, across a muddy brown pond floating with quacking ducks and geese, is the bank from which Hamilton and his friends watch the herons. Trees line much of the bank, but don’t inhibit a direct view into the colony for Hamilton and other spectators.

“It’s a great place to come see the spectacle, witness the life cycle,” Hamilton says.

He visits many other area heron colonies, including a close-to-home Lake Sammamish colony, but has not seen another colony as large or accessible as Black River’s.

With two herons to a nest, this year’s 80 Black River nests mean there are about 160 herons.

Chris Anderson, a wildlife biologist with the state Department of Fish and Wildlife, says that’s about average for the heron colony, which is King, Pierce and Snohomish counties’ largest.

In addition to its size, Black River’s heron colony is unique for the proximity of its next-door neighbors: two bald eagles living in a nest just 400 yards east.

“We don’t have another colony in King County with eagles nesting that closely,” Anderson says.

But eagles are not uncommon in heron colonies. While not all colonies host resident eagles, Anderson says most King County heron colonies fall victim to eagle raids. Eagles seem to be the herons’ most common predator, Anderson says.

Black River’s colony is no exception. Hamilton and other observers have witnessed eagles attack the colony, in pursuit of eggs and chicks. Eagles rarely bother adult herons, Anderson says. Black River’s eagle pair destroyed the first round of last year’s heron eggs.

“The eagle stuff is brutal, just bone chilling,” Hamilton says.

The eagle’s predatory nature is reflected in their new nicknames: Bonnie and Clyde. Hamilton trains his telescope on the pair during a recent visit. Bonnie is in the nest, but just the yellow of her her beak and the white feathers atop her head are visible. Clyde is perched on a branch above the nest. Clyde wears a leg band, Hamilton says, and Bonnie is bigger and has a fatter face than Clyde.

“Hopefully they’ll stay there,” Hamilton says.

Although bald eagles and herons have about the same six-foot wing span, eagles have about four pounds on the six-pound herons.

Black River’s eagles showed up about three years ago, Hamilton says. The original female died in her nest, and then Bonnie moved in. The eagles moved farther away for a year, but then returned to their nearby nest, which is in the former heart of the heron colony.

Anderson can’t predict what ultimate effect the eagles will have on the herons. What’s noteworthy is that the herons have persevered.

“The heron colony is still large, still producing,” Anderson says.

Although Hamilton says watching the eagles prey on the herons can be disturbing, he and his viewing buddies are glad the herons returned to Black River this spring. Herons don’t migrate, but many winter in nearby wetlands.

Black River’s heron colony began in 1986 with just three nests. The colony boasted about 135 nests from 2002 until 2006. But the herons’ return to the forest — the site of the former Black River — is never guaranteed.

Suzanne Krom of West Seattle has been watching over Black River’s herons almost since the colony’s beginning. She founded the advocacy group Herons Forever in 1989.

Krom has spotted herons gathering in a number of South King County shoreline spots.

“It’s very clear they’re looking for alternative nesting areas,” she says of Black River’s herons.

Aside from the eagles, Black River’s herons are threatened by looming construction above their habitat. In 2000 an Oakesdale office complex replaced the part of the forest that served as a protective buffer for the herons. In 2005, 26 acres of hillside above the colony was cleared for a 65-house complex called Sunset Bluff. Construction could begin late this summer. Nine acres of the same hillside were rezoned for single-family housing in December.

Krom fears the new housing developments could adversely impact the herons. But for now, viewers like Hamilton are determined to enjoy Black River’s herons.

Hamilton has been visiting the colony for several years. His first visits were on Boeing lunch breaks. His visits increased after his wife died five years ago, and he came to the forest to get away.

“It’s a tranquil place,” Hamilton says. “I have an emotional attachment to the herons.”

Nesting season lasts until the heron chicks leave the nest, which can be any time from Memorial Day through August. The herons disperse for the winter and will hopefully return to Black River Riparian Forest next spring.

But for now Hamilton is focusing on the present. The herons are back, and despite the threats from the eagles and ensuing development, he has to assume they’ll have another successful season.

“They’ve got a good start, a better start than we thought they would get,” he says. “Full speed ahead.”

Emily Garland can be reached at emily.garland@reporternewspapers.com

or 425-255-3484, ext. 5052.