Numerous displays lead up to the mating of great blue herons – neck stretching, bill clacking, wing preening, circling flights, twig shaking, crest raising, neck fluffing, to name but a few. After this elaborate courtship comes copulation, which is not nearly as showy. Copulation typically takes place on the nest. The male places one foot gently in the center of the female’s back. The female leans forward, bends her ankles and holds her wings slightly away from her sides while the male lowers himself, often flapping his wings. Once the job is done, the male flies off. If you look closely you can perhaps make out that the male is grasping the female’s head/neck while copulation takes place.
Birds have a number of ways of keeping cool, which is a good thing, given the number of hot days we’ve experienced this summer, and probably for summers to come. They don’t sweat, nor do they pant, but birds do have several behavioral adaptations which reduce their temperature. Often, while exposed to the relentless heat of the sun, Great Blue Heron nestlings resort to what is called gular fluttering. They open their mouths and “flutter” their neck muscles, promoting heat loss – an avian version of panting. An even easier behavior to observe is the position Great Blue Herons will often assume on a hot day. They droop their wings (see photograph) while standing, which allows air to circulate across their body and sweep away the excess heat.
Although Great Blue Herons are colonial nesters, they forage by themselves, usually by slowly wading or standing in wait of prey in shallow water. Fish are the mainstay of their diet, but they also consume amphibians, invertebrates, reptiles, mammals, and birds. When prey is located (by sight), the heron rapidly thrusts its neck forward and grabs it with its beak. If it is small, it is sometimes tossed in the air before it is swallowed, as the photograph depicts. Most prey are swallowed whole.
I had to laugh recently when I noticed a chain reaction going on in a Great Blue Heron nest I was watching. There were five chicks, and one of them yawned. At least I presume it was a yawn, though perhaps it could have be re-aligning its beak or perhaps cooling off. Exactly like humans, each of the remaining four birds followed suit and proceeded to stretch their beaks open wide in succession. It struck me as quite comical, especially when I discovered myself yawning as I observed the heron chicks doing the same.
Great Blue Heron chicks are getting big enough so that you can easily observe them (can you find all four?). Occasionally you can even detect flies and other insects buzzing about them, which, given the fact that nest sanitation is not a priority for herons, is not surprising. While the parents do toss the eggshells out of the nest, feces, partly eaten prey and even dead chicks often remain in the nest. Also, parents feed their young by regurgitating into the nest and the chicks will regurgitate when disturbed. Unlike most song birds, Great Blue Herons re-use their nest year after year. It is quickly apparent why they add more sticks and boughs to their nest every breeding season – were that housekeeping for humans was that simple!
Great Blue Herons are returning to their breeding grounds in northern New England, where they typically nest in colonies. Unlike the nests of songbirds, heron nests are re-used year after year. While an individual heron does not usually choose the same nest every year, they usually return to the same colony. While some colonies are active for only a few years, some have been known to be active for over 70 years. Because nests can be located up to 100 feet high in a tree (typically a dead snag in the Northeast), you rarely have a bird’s eye view of nesting activity. However, if you go to Cornell’s new live great blue heron web cam site (http://www.allaboutbirds.org/page.aspx?pid=2433 ) you can see every movement made by the great blue herons currently nesting in Sapsucker Woods in Ithaca, NY.