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Great Blue Heron

Great Horned Owl Nestlings About To Fledge

5-17-19 great horned owls_U1A8938Great Horned Owls do not build their own nests, though they may provide some lining to an existing cavity or nest. Snags, cliffs and man-made structures provide nesting sites, but most commonly Great Horned Owls use the tree nests of other species such as hawks (especially Red-tailed) crows, ravens and squirrels. Most, but not all, nests are used for only one season. Pictured is a Great Blue Heron nest that has been usurped by a Great Horned Owl family – a feat achieved by the owls claiming the nest as early as February, prior to the return of herons.

After incubating her eggs for roughly a month, the female Great Horned Owl then broods her young for two to three weeks. The father’s role consists of bringing food to the female while she is incubating and brooding. She then tears the food up into bite-size pieces for the nestlings.

When the nestlings no longer need the heat their mother’s body provides, brooding ends but the mother stays with her nestlings until they fledge at about seven weeks of age. (Pictured: Great Horned Owl mother and two downy nestlings, roughly six weeks old. Thanks to Marc Beerman for photo op.)

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Great Blue Herons Building & Renovating Nests

5-6-19 great blue heron with white pine2_U1A7932A visit to a Great Blue Heron colony at this time of year will be rewarded with a great deal of avian activity, for their nesting season has begun and renovations are going full tilt. Males usually arrive first and settle on nests (more often as not using a different nest from last year) or begin building their own. Courtship then begins.

Great Blue Heron nests are found primarily in trees, up to 60 feet or more above the ground. Where trees are not available, herons will nest on the ground (usually only on predator-free islands). Males gather sticks and other nesting materials from the ground, nearby trees and shrubs, or from unguarded and abandoned nests, and females are usually responsible for the placement of the sticks into the nest. Nests are often reused for many years. Pictured is a Great Blue Heron returning to its nest with a branch from a White Pine tree which will be used for lining the nest. Nesting material is added throughout the nesting period.

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Lingering Great Blue Herons

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Most fish-eating birds that breed where most bodies of water freeze over in the winter migrate further south in the fall, including Great Blue Herons.  Movement of this large wading bird takes place largely from September to mid-October. According to Christmas Bird Count data, the Great Blue Heron has the widest wintering distribution of any heron species in North America.

While the number of Great Blue Herons in the Northeast is greatly diminished in November and December, it’s not uncommon to spot lingering birds at this time of year.  Come January, when most bodies of fresh water are inaccessible to herons, sightings become rare until they begin returning in March.

Where open water remains in the Northeast, those Great Blue Herons braving the cold continue to consume fish, insects, amphibians and crustaceans.  Small mammals, especially voles, and birds remain a warm-month delicacy, when mammal hair is cast in pellets and bones are digested.

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Great Blue Heron Chicks Enjoying Home Delivery

7-18-18 gbh chicks & parent IMG_5874Great Blue Heron chicks spend roughly two months in their nest before fledging, during which time they are totally dependent on both of their parents for food.  During the first week after their eggs have hatched, the parents return to the nest after foraging and stand on the rim while placing regurgitated food into their chicks’ open beaks.  By the second week the chicks grasp the adult’s beak briefly when the parent arrives with food, and by the end of the third week the chicks are pulling the adult’s beak into the nest, which they continue to do until they fledge.  Occasionally chicks reach into an adult’s open beak to get food, but most of the time the parents put the food into their offsprings’ beaks.

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Fishing Methods Of Birds With Spear-shaped Bills

10-10-17 great blue heron with fish 049A5631How do herons, egrets, bitterns, kingfishers, loons and other fish-eating birds with spear-shaped bills capture their prey? Do they use their bill as a spear and pierce through a fish, or do they grab the fish between their mandibles? You often read about one of these birds “spearing” a fish. However, a majority of these birds, most of the time, do not spear fish, but open and shut their bills fast enough to capture a fish in them — the spear shape of their bill lends itself to the tong-like action it performs. In addition, its shape enhances the movement of the bill through the water as the bird dives (its head or body) into the water to grasp the fish between its upper and lower mandibles.

One exception to this rule is the Anhinga, which does run its bill (which is equipped with backward grooves to prevent slippage) through fish in order to capture them. After spearing a fish, an Anhinga then shakes it vigorously off its bill, tosses it in the air, and catches and swallows it headfirst. (Photo: Great Blue Heron)

 

 

 


Low Water Levels Provide Palette for Tracks

10-27-16-tracks2-1The 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.

 Under cover of darkness, White-tailed Deer, Mink, Raccoons and a variety of birds and small mammals frequently visit and leave traces of their presence in the form of tracks. Other creatures whose tracks you may well find in the exposed mud of wetlands this year include Beavers, Muskrats and River Otters.

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Silver Lining to Low Water Levels

9-27-great-blue-heron-20160911_7746The 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.

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Great Blue Herons Cooling Off

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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 Mating

4-15-15  great blue herons copulating2  IMG_8954Great 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.

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Great Horned Owls Incubating Eggs

4-1-15 GHO2  240Great 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)

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Great Blue Heron Casting Pellet

great blue heron casting pellet 205Great 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.

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Herons, Egrets and Bitterns & Their S-shaped Necks

9-4-13  great blue heron 1486If 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.)

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Great Blue Herons Mating

4-22-13 great blue herons copulating2  IMG_8954Numerous 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.