The great blue heron (Ardea herodias) rookeries at Baum Lake (Shasta County CA) are teeming with activity. In one ponderosa pine alone I can count a minimum of fifteen nests. Females are incubating eggs in some of the nests and some nests contain chicks that are already well-developed – and chicks at intermediate stages of growth in other nests.
Because of their height it is impossible to see the pale blue eggs in the nests. The female lays two to six eggs which hatch after 27 to 29 days. I did find a discarded heron egg shell at the base of a ponderosa. Rodents and other small mammals eat the shells as a source of calcium. The blue color of a heron egg shell also fades in the sunlight. Thus I believe the chick hatched from this shell shortly before I found it.
A great blue heron nest can be a small platform less than two feet across or after many years of use the nest can grow to four feet or more across. This nest with a parent and at least one young chick was fairly compact, suggesting that it has not been used long. Chicks are born with their eyes open and covered in down.
Another nest containing four young birds was much more extensive, probably already used for many seasons. These babies appeared to be the most developmentally advanced in the tree.
While the parent stood to the side (its lower body can be seen on the right) the youngsters interacted with each other. They moved about in the nest and often one young heron would put its bill into another’s bill. I do not know if this mimicked feeding or if it was just a form of play.
The babies also spent time flapping and strengthening their wings. It is easy to see how a young bird could fall out of its nest. I held my breath several times when a young bird with outstretched wings seemed to lose its balance and teetered on the edge of the nest. Thankfully I did not see any falls.
Sometimes the heron nestlings do sit quietly for a few moments. I always think of a row of vultures when I see this picture, especially the heron second from the left. Great blue heron chicks remain in the nest from 49 to 81 days. The young in this nest are growing fast.
(Click on a picture to get a better view.)