Great blue heron nests have always struck me as an example of hope overriding probability. To my eyes, they appear to be dubious creations, typically a modest assemblage of sticks lodged high in the top branches of a dead tree, wickedly exposed to all manner of the elements. They’re expected to serve as the home of as many as half a dozen young herons for nearly three months of the summer. In my limited experience around heron rookeries, most don’t make it.
I’ve been keeping an eye on a new heron rookery near Lost Lake this summer. While many heron rookeries can be used for decades, they do tend to shift across the landscape over time as the dead trees they prefer eventually fall apart. Which means they’re always on the lookout for a new location that offers the criteria they tend to prefer.
Herons like nesting in the tops of dead trees in our area, which provides the easiest access for the parent birds, with their long legs and six-foot wingspans.
The trees, mostly black ash in this case, were killed when beavers flooded a large lowland area a few years ago. I noticed four or five nests that appeared for the first time at the site this summer. I assumed some were practice nests since I never saw any young in them, but at least three did have nestlings. As of last weekend, when I donned my rubber boots and camo and waded out into the tangle of downed trees and murky water, young ones remained in just one of the nests and the two young birds certainly looked ready to fledge any moment.
Unlike most smaller birds, which may only spend 10-12 days in the nest after hatching, great blue heron chicks remain in the nest for anywhere from two to nearly three months.
This late in the summer, I didn’t expect to see any sign of adult birds, since they begin to stay away from the nest to force the young birds to finally strike out on their own. As long as the adults keep feeding the young ones at the nest, their incentive to leave is limited, a fact that many human parents have discovered as well.
The immature herons pictured above were certainly as large as their parents by this point, although they can be distinguished most readily by the brown streaking on their breasts. At this point, the young birds should have been fully capable of flight, so once they get hungry enough, they should be on their way.
The site appears to be a decent one for a heron rookery, with water surrounding the trees, which should provide at least some deterrence for mammalian predators. Their biggest threat is from the air. When young, the herons are potential prey for large hawks or eagles, although once fully-grown, they make a formidable target, even for an eagle. I certainly wouldn’t want to get in the way of that dagger-like bill, which herons can deploy at lightning speed and with remarkable accuracy.
The threat from aerial predators is one reason that herons form rookeries, which can grow to hundreds of nests in some cases. There is strength in numbers and it’s easy to see why a predator might think twice before descending into the midst of dozens if not hundreds of adult herons looking to grab a nestling.
Given that these herons had at least some success in their new location this year, I would expect that herons will return next year. They’ll typically add a few more sticks to their existing nest, growing it over time, just as we humans like the occasional addition, particularly when we’re growing our own families.