Friday, July 13, 2012

The Little Blue Heron at Brazos Bend

This week’s rainy daytrip to Brazos Bend State Park gave me chance to study and photograph several of the “locals”; those beautiful Aves that make this upper gulf coast habitat their year-round residence.  I’ve decided to break apart my “trip report” into multiple blogs, focusing attention and photographs on unique species sighted as well as an upcoming blog on current habitat conditions.  My first post was about the Anhinga.  Today I want to post photos of the Little Blue Heron.

Herons, Egrets and Bitterns are members of the Order Ciconiiformes (which also includes storks, ibises, spoonbills, and vultures) and the Family Ardeidae.

Ardeids are not vegetarians.  These carnivores are expert fishermen.  It is great fun to watch their innate stealthy-slow movement of long legs and necks, and then sudden forward thrust of body and bill to spear a fish or frog or other aquatic animals.  It can be comical to watch an Ardeid spear an oversized fish with their long pointed bill and then attempt to maneuver the fish off of their bill and into their mouth for a single “down the hatch” dinner.  It took Tom Hank’s character in “Cast Away” a good number of years to acquire this life-saving skill.  The spearing, that is.  I have to believe these expert Aves fishermen were role models for the nonfictional Native American fishermen of centuries ago.

Some of the Ardeid species exhibit what ornithologists call “polymorphism” of plumage.  Simply said, a species can have either light or dark-colored plumage, and birders will refer to sighting a “light morph” or a “dark morph” individual.  The Reddish Egret is most commonly sighted as a dark morph—a slate-gray body with reddish neck and head.  But birders love sighting the white-morphed Reddish Egret, simply because it is the statistically rare morph (Sibley’s estimates a 2-7% population of light-morphed Reddish Egrets on the gulf coast.)  These Reddish Egret light and dark morphs carry their plumage coloring throughout their lives.  It can be great fun to get a group of birders started on a discussion of the multiple current theories for this type of lifelong polymorphism. I can just sit back and watch the opinions fly.
The Little Blue Heron’s polymorphism is age specific.  The juvenile (early summer birth date until the following spring) is an all white morph.  The yearling Little Blue Heron is white with a mottling of dark gray feathers.  And the mature adult (by second year) is a beautiful dark gray-blue bird with a dusky-purple neck and head.

If you own a birding guide with pictures (or a computer with common search engines), take a look at the polymorph pictures of the Great Blue Heron, Reddish Egret and the Little Blue Heron.  Look carefully at their bill shapes and colors and compare those with the Great Egret and Snowy Egret.  Bill shape and bill coloring can be a great identification marker when viewing a potential white morph in the field.  The bill color will cleanly differentiate a white morph of a common dark species (such as a Reddish Egret) from other un-morphed white species such as the Great Egret or Snowy Egret.  
I won’t soon forget my first Freeport Christmas Bird Count (CBC) several winters ago when I took a too-quick binocular glance at a distant white-morphed Reddish Egret standing still against marsh grasses.  I assumed it was a Great Egret, expressing my confident opinion to the seasoned birder that I was shadowing for this CBC day.  “John” gently corrected my mistake and explained the bill markings and other field markings of this white-morphed Reddish Egret.  My moment of embarrassment quickly turned into a teachable moment and an extraordinary day of learning.
And so whether a beginning or seasoned birder, the summer season of birding at Brazos Bend State Park gives ample opportunity to sight and study the age-related polymorphism of juvenile, yearling and mature Little Blue Herons.
A beginning birder might glance at this juvenile and mistake it for a Snowy Egret.  But its bill, eye and leg coloring instantiate it to be a juvenile Little Blue Heron:

My favorite sighting is the yearling Little Blue Herons with their differing degrees of mottled gray-and-white coloring.  I spotted these two yearling Little Blues practicing the ways of patient fishermen:

And a photo of the beautiful 2+ year old Little Blue Heron, a probable parent to one or more of the many juveniles I spotted that rainy day:

The Little Blue Heron at Brazos Bend is worth a closer look, especially on a hot and rainy summer day when multiple generations of this Ardeid can be found fishing or eating or just sitting still and admiring the great outdoors.  Kind of sounds like my family’s yearly summer reunions.

1 comment:

  1. "It can be great fun to get a group of birders started on a discussion of the multiple current theories for this type of lifelong polymorphism. I can just sit back and watch the opinions fly."

    I was just trying to decide today what polymorphism theory I would assign assign myself to. I had to stop for fear my head was going to explode.

    Your laughing, smiling, find the humor in every situation RN



I no longer accept Anonymous Comments. Please use your Google account to sign in and leave a comment.