Here is one example of what might eat a heron. In Washington state, Bald Eagles are eating Great Blue Herons in the nest.
Near a small pond on Renton's western edge, nests of great blue herons, perched up to 100 feet high in a stand of cottonwood trees, appear safe from any danger from below.At one location, eagles started nesting near a heron colony after the eagles' original nesting site was cleared for development. After that, the number of young herons fledged from the nests dropped from 360 in 2004 to less than 50 last year. However, it is not clear how much eagle predation is hurting the heron population as a whole. Great Blue Herons are declining in the Pacific Northwest, but other causes could be a factor as well.
But not from above. ...
Particularly during the breeding season, now under way, heron watchers report seeing eagles chasing herons off their nests, then preying on the eggs and hatchlings left behind.
"They'll eat the young right there on the nest, or carry one off," said Pam Cahn, a volunteer with Heron Habitat Helpers, which monitors and helps maintain a nesting ground in Seattle's Kiwanis Ravine near Discovery Park.
Eagles also will sometimes attack an adult heron. O'Keefe saw an eagle with an adult heron in its talons near his Vashon Island home. "The eagle took it down to the ground and finished it off," he said.