Great Blue

I spotted a new Blue Heron rookery today, thanks to the dozen or more herons flying around a huge wetland on the outskirts of town. I'm sure my jaw dropped; I've never seen this many herons together before. They're common in the valley, because of all the ponds and marshes, and we see them on our own pond from time to time. But seeing so many circling the marsh was really a thrill. I was hoping to find a place to park and watch for a while, but the only nearby parking was at the animal control shelter, and the gates were locked. I've never seen this group of nests before, in spite of driving this stretch of road nearly every day. So I'm thinking it's a new, under-construction heronry.

A couple of years ago I found a heronry close to my house, in a stand of dead trees in a county park. I would never have seen the nests except for the pair of herons that flew across the road right in front of my truck, each carrying a long stick. As I turned my head to watch them fly into the trees, I spotted the group of nests.
When I got back to work, I got curious about their breeding habits and did some online research. The Great Blue Heron usually breeds in colonies, building their nests in trees close to lakes or other wetlands. The colony is correctly called a heronry, although more often I hear them referred to as a rookery. Once the birds choose a mate for the year (they're monogamous for a single breeding season), each pair builds a bulky stick nest high in a tree, usually at the crown, or the top of a standing dead tree. The female lays 3 to 6 pale blue eggs, each about the size of a chicken egg. Eggs are incubated for about 28 days, and hatch over a period of several days. Hatchlings will fledge (take their first flight) and reach their full adult size in about two months. The birds are wary of humans, particularly at the beginning of the nesting process. Repeated human intrusion into nesting areas often causes the birds to abandon the nest (and the eggs or chicks). If you want to observe the nesting of herons, stay back and use binoculars. If you get too close, body language will tell you if the bird is disturbed by your presence. Pay attention, and back off until the bird relaxes.
An adult Great Blue Heron has a head-to-tail length of 38–54 in., a wing span of 66-79 in., a height of 45–54 in., yet only weighs 4.6–5.5 lb. Because of their size, adult birds have few natural predators, but can be taken by bald and golden eagles, and less frequently, great horned owls and red-tailed hawks. The eggs and nestlings can fall prey to turkey vultures, hawks, bears, and raccoons. The biggest danger to the heron is habitat loss, starvation (associated with habitat loss), human disturbance, and disease.
The Puget Sound area has a unique subspecies of the Great Blue Heron, which is non-migratory. It doesn't interact with migrating herons, and has developed adaptations that include a darker plumage. It's classified as Ardea herodias fannini.