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Posts tagged “Ardea herodias

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

11-12-14 great blue heron2_U1A1373

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)

 

 

 


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 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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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.


How Great Blue Herons Stay Cool

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.


Great Blue Heron Fishing

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.


Great Blue Heron Chicks Yawning

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 Nests

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 Return

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.