In the spring Great Blue Herons gather in large groups to raise their young. Known as colonies, rookeries, or heronries, the groups increase the birds’ security by ensuring that predators can’t approach undetected. They’re often on islands and the nests are 50 feet up or more.
This rookery is in Minneapolis, on a tiny island in the Mississippi, just north of downtown. I took these photos in March when the birds were building their nests and competing for space; it was a raucous scene. I had a 600mm lens on an APS-C camera, but I was over on the shore, not the island. And actually you don’t want to get any closer, as these very large birds may attack you and can really do damage with those beaks.
The males fly around gathering sticks and twigs. The swoop around dramatically when they return, putting on a good show.
They present these materials to the patiently waiting females, who weave them into large and substantial nests.
This rookery is a spinoff of a much larger one that was destroyed by a tornado in 2011. With dozens of large, squabbling birds in just a few trees, it gets crowded.
Males and females aren’t visually distinguishable – by us, anyway; the males are somewhat larger. Nest building takes a couple of weeks, then the eggs are laid, and incubated for about a month.
This panoramic photo shows the entire colony – click it for a larger image.