This is the week to check out the great blue heron rookery at North Mississippi Regional Park (or the one at Coon Rapids Dam too). I headed out to the North Mississippi rookery yesterday to take a look, right now the nests are very visible--even without binoculars.
You can get a great view of all sorts of behavior including nest building as the herons are coming in from migration. Some have been at this rookery for a few weeks already.
Quite a few of the herons were perched on or near a nest and not moving. I read on Cornell's Birds of North America Online that like many migratory bird species, males arrive to the nesting grounds first and establish who is taking what nest. From there, when not foraging for food, a male will spend all his time at the nest. Perhaps these were males waiting for a female to court or hoping to prevent other males from stealing sticks for their nests.
A few herons were already incubating eggs. These nests will either be way ahead of the game with chick rearing or have to start over in a few weeks. We are heading out of an unusual March--no snow in the Twin Cities at all. This is highly irregular, March is technically our snowiest month. It's not out of the realm of possibility for us to get snow in April. I'm loving the opportunity to bike on the trails a whole month early, but I'm not going to hold my breath and say that we are totally free of snow for the rest of the spring. If we get a cold snap, these already incubating herons may risk losing young and have to start over. But that's what birds do.
So, take a moment to head to one of our heron rookeries before the leaves are out. You can always somewhat see the nests at North Mississippi Regional Park and Coon Rapids Dam but it's ten times easier to point them to kids before the leaves are out. If this 70 degree weather keeps up, that could be rather soon...aw man, that means that leaves will be well out when warblers get here in May. That's going to make warbler watching a challenge.
UPDATE 2011: This heron rookery was destroyed by a tornado that ripped through Minneapolis in May, 2011. All the nests were destroyed. The birds did renest, some up river at Coon Rapids Dam and others at a new site at the Riverside Power Plant near the Head of Navigation on the Mississippi River. Most of the young did not survive, but the few that were rescued were eventually released later in the summer.