The GBH's are back!

After seeing that the Great blue herons had returned on March 13, I went to check on the heronry (also known as rookery, which is a colonial nesting area) yesterday afternoon. I only checked on the nests on the north side of the river, but found 8 of them were intact. This afternoon, I'll go check on the nests on the south side of the river to see if they made it through the windy winter. As the Great blue herons return, some of the males will choose old nests and defend them as territory. Other males will begin the construction of a new nest. Last spring, 12 new nests were built after being knocked down the winter before.

Great blue herons typically arrive in Iowa during late March and early April to nest. They start with ritual courtship dances, which are taking place right now here at Whiterock. The males will collect branches and as he returns to the nest, the female will stretch her bill up towards the sky making a "arrroooo" noise, while the male will raise his crest and make croaking noises. Anothef display involves the birds clapping their bills together and attempting to clasp the other birds' bill. The female takes the nest material and works it in to the nest, which is generally located in a dead tree or dead limbs of trees 30-70 feet above the ground. At Whiterock Conservancy, the nests are located in cottonwood in the floodplain and dead elm trees on the ridges above the Middle Raccoon River. Three or four pale blue eggs are laid which hatch asynchronously (hatching one or two days apart) nearly four weeks later during May. The young fledge during July and stay with the family group for the summer to hunt and fish around the colony before migrating south.

There are a number of different species of waterbirds that nest colonially in the state of Iowa, among them are Double-crested cormorants, Black-crowned night herons, Yellow-crowned night herons, green herons, little blue herons (one record from 1984) cattle egrets, and great egrets. Double-crested cormorants are found at Whiterock Conservancy during the spring and fall migrations and green herons nest here, but no colonial nests have been found on the property. Look for one pair of green herons nesting by the last pond on the north side of the main trail located one miles east of the campground. Last year, a Great egret was seen "hanging out" around the Great blue heron rookery for three days, but left. Occasionally, these two species have been known to nest together in a colonial situation. We can only hope!