I discovered a great blue heron rookery today at Kensington Metro Park in Milford, Michigan. It's quite an awesome sight. All photos taken there are labelled KP. This gallery also contains photographs of a great blue heron rookery located in the West Bloomfield Nature Preserve in West Bloomfield, Michigan. Photos labeled WB were taken there.

"The male and female build a nest, which is a large platform of loosely woven sticks. The male gathers the nesting material and presents it to the female, who uses her bill to work it into the nest. New nests may be about 45 cm (about 18 in) across and older nests that have been expanded for several years can reach 1 m (over 3 ft) across. The nests are built 6 to 30 m (20 to 98 ft) above the ground.

The female lays three to four large pale blue-green eggs one or more days apart. Both parents take turns incubating, or warming, the eggs by sitting on them. To keep the eggs evenly warmed, the parent stands up and turns them with its bill about once every two hours. The young hatch after 25 to 29 days in the order the eggs were laid. Both parents feed the young by regurgitating partially digested fish. Usually only one or two of the oldest chicks survive, since they are larger and better able to compete for food. The young herons begin to fly about 60 days after hatching and leave the nest after another 5 to 30 days."

"Great Blue Heron." Microsoft® Encarta® 2006 [DVD]. Redmond, WA: Microsoft Corporation, 2005.
Microsoft ® Encarta ® 2006. © 1993-2005 Microsoft Corporation. All rights reserved.

Anyone seeing these photos should keep in mind that the rookeries here are very different from the Venice rookery in Florida. The Venice rookery is on an island where the nests are built close to ground level. One photographs there at eye level; the island is much closer to the shore; and consequently it is easy to capture the activities that are taking place: https://pbase.com/drjaysel/venice_rookery .