The low water levels in our ponds this fall do have one benefit – visitors leave obvious signs in the exposed muddy banks. It is fairly astounding how much nocturnal and crepuscular wildlife regularly visits these spots and remains undetected by humans under normal conditions.
The low water level of most small ponds and streams this fall has at least one silver lining, and that is that consumers of fish and other aquatic creatures expend far less energy finding prey, for it is all concentrated in much smaller bodies of water. The few puddles of water in small streams contain a vast amount of life, as do small ponds.
The Great Blue Heron has the advantage of having a varied diet that is found in a variety of habitats, so it forages in grasslands, marshes, intertidal beaches, riverbanks and ponds. While amphibians, invertebrates, reptiles, mammals, and birds are all known to have been eaten by Great Blue Herons, fish are their mainstay. They often forage in ponds, where they typically wade or stand in wait of prey in shallow water, which has not been in short supply this summer and fall. While the low water level is wreaking havoc with beavers and muskrats, it provides bountiful fuel for herons, egrets, kingfishers and other birds that forage in small ponds and streams as they wend their way southward.
Birds have a number of ways of keeping cool. They don’t sweat, nor do they pant, but birds do have several behavioral adaptations which reduce their temperature. Often nestlings that are exposed to the relentless heat of the sun for long periods of time, such as platform-nesting raptors and herons, resort to what is called gular fluttering. They open their beaks and “flutter” their neck muscles, promoting heat loss – an avian version of panting.
Another avian strategy for cooling off is demonstrated by this adult Great Blue Heron — that of arranging its wings in a certain position in order to reduce its body heat. Great Blue Herons droop their wings while standing, which allows air to circulate across their body and sweep away the excess heat.
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Great Blue Herons have returned to their nesting colonies in the Northeast and their breeding season is underway. These birds are monogamous for the duration of any given breeding season. A study found that most Great Blue Herons choose a new mate every year. After elaborate courtship displays have taken place, the pair copulates, frequently on the nest, and usually in the early morning or evening, as the female is away from the nest mid-day.
Great Horned Owls are said to have the widest range of nest sites of any bird in North or South America. Like other owls and falcons, this raptor does not build its own nest, but rather relies heavily on abandoned stick nests of diurnal birds of prey. Red-tailed Hawk nests are often usurped, as well as those of Bald Eagles, crows, ravens and herons. Nests may be lined with shreds of bark, leaves, downy feathers from the owl’s breast, fur of prey and trampled pellets. In addition to bird nests, Great Horned Owls also raise their one to four nestlings (usually two) in tree cavities and snags, on cliffs, in deserted buildings, in squirrel nests and even on the ground.
The female Great Horned Owl does all the incubating; the male delivers prey to her at intervals throughout the night. These early nesters have incubated eggs successfully when outside temperatures have been as low as -27°F. Hopefully warmer temperatures will welcome the newly hatched owlets in about a month. (photo: mostly hidden Great Horned Owl in Great Blue Heron nest)
Great Blue Herons swallow their prey whole, which means they consume not only flesh, but also bones and fur (if they eat a mouse or a vole). They are able to digest almost all of the prey that they eat due to acidic stomach secretions that are capable of softening even bones. However, they are not able to digest hair, or fur. This indigestible matter is formed into pellets which Great Blue Herons regurgitate – much like owls and many other birds.
If you’ve watched a heron, egret or bittern for any amount of time, you know they strike suddenly and rapidly at their prey . They can do this because of the structure of their neck bones. According to David Sibley, modification of the sixth cervical vertebra lets them draw their neck into an “S” shape and then shoot their head and bill forward with lightning speed. This adaptation also allows these birds to fold their neck while flying, which improves the aerodynamics of their flight. (Photograph is of a Great Blue Heron.)