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Posts Tagged ‘nestlings’

To celebrate the Heron Observation Network’s fifth year, I put together a collection of Photos from the Field, taken by myself, co-workers, and some very talented HERON volunteers.  Many THANKS to all the HERON volunteers who monitored colonies, and to the landowners that allowed access.  Here’s to another exciting year ahead of us!  Happy 2014!

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Snowy egrets perched in apple trees.

This past May, I had the unique opportunity to assist National Audubon Society (NAS) with a wading bird census on Stratton Island in Saco Bay.  Part of NAS’s Phineas W. Sprague Memorial Sanctuary, this 23-acre island is located 1.5 miles south of Prout’s Neck and is home to an immense diversity of wading birds, waterfowl, seabirds, and songbirds, and is an important stopover for all the above during migration.

In fact, Stratton Island hosts the most diverse wading bird colony in Maine, and is the most northerly U.S. breeding location for a few of these species.  On the north side of the island, great and snowy egrets, black-crowned night-herons, little blue herons, and glossy ibis layer their nests in among the branches of choke cherry and apple trees.

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We’ve had some hot sultry days this summer, and if you were smart you retreated to a shady spot or went for a swim at a nearby pond.  But what about all those great blue heron nestlings that were sitting in their nests 20-100 feet up in a  tree, often in full sun?  Sure, their nest tree may be surrounded by water if it is a snag in a beaver flowage, but that water is completely inaccessible to a nestling who takes around 80 days to learn how to fly. 

How do they keep cool on those 90+ degree days?  Like humans, birds rely on evaporative cooling to release heat; however, birds do not have sweat glands like you and me.  Instead, they lose heat through their respiratory tract.  Some birds do this by panting, but others, including herons, do so by “gular flutter”.  Gular flutter is a rapid vibration of the upper throat and thin floor of the mouth.  By opening their mouths wide and rapidly flapping the thin gular membranes of the throat, they expose a large featherless area to moving air.  To see what gular flutter looks like, click on the link below to a web album containing 2 short videos:

Gular Flutter Videos

Herons may also change their posture to keep cool.  The “sunbathing” posture or “delta-wing” is sometimes assumed to aid in cooling the bird itself as well as to help shade its nest contents (eggs or nestlings).  Often sunbathing is accompanied by gular flutter.  The sunbathing posture I witnessed below was seen in mid-May on a day that was not noticeably hot (at least to me, but I was shaded by a blind).  This adult most likely had eggs or newly hatched young in the nest, but it doesn’t appear that the sunbathing posture is serving to shade any nest contents here.  The adult is actually facing into the sun.  Perhaps this is one of many reasons that led to this nest’s failure?  It was inactive only 1 week later.

Adult great blue heron “sunbathing”.

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Molly Meserve is a graduate student at the University of New England.

Hello, my name is Molly Meserve and I am a graduate student at the University of New England in Biddeford, ME. Along with all of you I will be closely observing the fascinating behavior of Maine’s Great Blue Herons this summer. As a Maine native I am particularly interested in this work because the Great Blue Heron has been a constant in my life here in Maine. My master’s thesis focuses on the following question: Do prey delivery rates and total foraging times of Great Blue Herons in coastal and inland colonies differ and how may these factors affect chick survival? With the help of Danielle D’Auria and some wonderful HERON volunteers I have been able to visit a few of the Great Blue Heron colonies in the State. Two of those colonies have been chosen as the main focus of my study; the inland colony is located in Hollis, ME and the coastal colony is in Brunswick, ME. I will be out in the field from April 1st until about mid-August observing from ground blinds that I have set up in each of the sites mentioned above. While in the field I will be focusing on gathering accurate numbers of adults, chicks (their approximate ages), and nestlings along with prey delivery rates and time spent foraging for each nest observed.

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Photo by Deb Dutton

June is when nestlings appear in most great blue heron colonies in Maine.  In Maine, great blue herons lay their eggs anytime between late April and mid-May.  After approximately 27 days of incubation, the nestlings hatch out mostly unfeathered except for pale gray down that appears a bit bushy on the crown.  They weigh less than 2 ounces at hatching and can barely hold their heads up.  Within a week or two they can be seen poking their heads above the edge of the nest bowl, especially when their parents return to the nest to provide food.  Within 7-8 weeks, the nestlings will grow to adult size, weighing in at 4.5 lbs and standing about 3 ft tall.  Check out a video clip of a heron nest with nestlings taken by Deb Dutton on Facebook!

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An adult great blue heron arrives ready to feed its nestlings. Photo by Ron Logan.

 [The short article and incredible photos below are from volunteer, Ron Logan, who monitors 4 great blue heron colonies for HERON.]

The season will begin in a couple weeks to monitor my 4 Great Blue Heron colonies. These pictures are from last year and were taken from quite a distance. Generally you can’t get very close to nests, since they are in wetlands and 20 to 50 feet in the air.  If you think feeding your babies was tough, or that dinner table fights with your siblings was a nightmare, imagine what it would be like as a Great Blue Heron. (more…)

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Five nestlings, all around 4-5 weeks old.

[Be sure to click on a photo for a larger view.]

Can you imagine raising 5 children in a 1-room apartment?  For great blue herons, it’s not all that uncommon.  In general, great blue herons lay 2-7 eggs, but I have yet to see more than 5 young in any nest.  I, along with many HERON volunteers, have remarked on the abundance of nestlings this year.  In a recent visit to a colony, I counted 87 nestlings in 32 nests!  And, those were the nestlings I could see…some nestlings were likely hunkered down in the nest or behind a branch out of my view.

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