Naturespeak A naturalist's view of the world

April 15, 2008

A New Hope

Filed under: Uncategorized — wykes @ 8:05 pm

 

Last May I featured the Great Blue Heron rookery at Kensington Metropark (see Naturespeak May 20, ’07). At that time of the year, the nests were brimming with young herons and the site was abuzz with activity and noise.  When I returned to the colony this year I found it to be a much quieter place. At this mid-April stage the nesting sequence has just begun, so I can provide you with a prequel to the late spring Heron saga (as a Star Wars fan I find this way of doing things perfectly natural).

  It appears that most of the nests survived the winter in pretty good shape (see here) so that improvement, rather than new construction, is the current need. It’s nice to know that at least one portion of the housing market has remained stable. The returning Herons have already staked their claims to their individual nests within the rookery – a process in which a male bird basically sits on a chosen site and pecks at anything that comes close. A lone Egret is again lurking around the place and likely will stake a claim within the heron neighborhood. He was apparently content with just perching down near the water’s edge until another egret shows up.

  Herons do not mate for life, so every year the males turn over a new twig and set up house-keeping with a different leggy chick. The courtship thing is a two way situation. After a whole lot of plume raising, head shaking, mandible clapping, howling, stick shaking, preening, and a little bill stroking, the mate choice is made and the pairs settle down and begin to get the nursery ready.

 I missed most of the elaborate courtship stuff, but was witness to the more subdued nest improvement stage. On this morning, the birds were spending a great deal of time just standing, or sitting, around. Several of the males were wrapped up in some excessive preening exercises. Part of this activity is done to impress the females, but most of it is performed for the sake of “look’n good.” The sinewy birds (up to 4.5 feet high) are glorious in their full breeding plumage. Long graceful black plumes project out of the back of their heads. These plumes stick straight up into air when the preener points the tip of his bill down to arrange the equally impressive set of neck fringe feathers (see above).  Scapular plumes (originating at the black shoulder epaulettes) pour down off the back. Their bills are colored an especially bright shade of yellow at this time of year.

  There is little difference between the sexes in this species, which is a good indicator that they share nesting duties. The females are responsible for most of the re-decorating, however. It falls upon the males to gather up the raw material. Being right in the middle of a laundry room do-over myself, I can appreciate this part of the process. One of the sticks I brought home did not please my mate but we are currently engaging in plume raising and should have this thing settled shortly – which means I will lose.

  Back at the rookery, I watched several males gracefully drop down to the undergrowth beneath the stately nest trees. They shopped for twigs – mostly rejects fallen from other nests – and after making a selection they flew back up to their respective nests. Being a bird endowed with a six foot wingspan the return ascent takes time and they must circle the island in order to lift their seven pound frame to the proper altitude.

  The female remains seated in the lofty nest during this time. As the male arrives with a branch, she greets him with an exaggerated stretched neck display and accepts the gift. Her “arroo” of approval may be answered by a throaty “kronk” from her mate, or the whole thing can be done in silence (such as when I presented a used cabinet to my mate as part of our laundry room project). The hen then carefully inserts the new twig into the framework and the male goes off in pursuit of an even better twig (see here- in lower nest). 

  On occasion, it seemed that the returning male came back empty-handed but was seen passing over something – perhaps a fine twiglet for the centerpiece.  These structures are really more like platforms and are not nests in the traditional sense. Even so, the egg holding portion is finished off with fine twigs, grass and even moss.  Over the years these nests can become quite large. It’s not unusual to see them reach an excess of four feet across which is the case with this set of nests.

  It can take weeks before the nesting project is considered “done.”  I believe this decision is ultimately made by the female based upon my own circumstance. Soon the couple will begin incubating their eggs.  I’ll show you a few next time, but right now I have to go do some preening.

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