Naturespeak A naturalist's view of the world

August 31, 2007

The Bluefoot Code

Filed under: Uncategorized — wykes @ 10:54 pm

Miss Percidae’s school class had just settled into their milfoil seats as she paddled into the room. The look on her face was gill struck and solemn as she approached the desk.  Barbell had just thrown a pea clam at Amia and feared that the teacher saw her commit the offense.  Miss Pericidae – normally “perky” Percidae to her students – was in no mood to address such nonsense. “Class,” she said, “we have a matter of great concern to address this morning.”  The bubbles trailing from her gill slits were tiny and regular.  None of the students had seen her like this before.

  “As you all know, we are approaching the time of great danger.  Now is the time for the blue raptor claw.”  The little fish suddenly giggled at the mention of this and the teacher firmly slapped her fin down.  Most of them were only small fry and had yet to experience any such danger.  The ever-present threat of Esox and Rappala were real enough, why concern yourself with something as rare as the blue claw. “This is not a joke,” she said in a tone that indicated her seriousness.  All eyes locked forward and mouths snapped shut at this statement.  She swam over to a rolled up chart suspended from the overhanging branch that formed the roof of the classroom.  With one fluid motion she grabbed the pull chord and unveiled this picture (see here).  All the fingerlings gasped and expelled a torrent of bubbles that joined together like a jellyfish bell and danced to the surface over their heads.

  Her picture was of a pair of deadly blue scaled feet equipped with sickle shaped talons.  The rough pebbly palms contrasted with the steel smooth surface of the claws. It was the blue raptor of storybook fame, but the image was frightfully clear and realistic. “This is a picture drawn by Monsieur Madtom Felis of the very claws that were seen in the water celery beds yesterday afternoon. This beast has already taken several of our cross river neighbors. Airbladder inspector Jung Sui narrowly escaped capture as he performed his duties at the swim club on Sunfishday”

   Ms. Percidae paused to allow the gravity of the situation to sink in and she was not disappointed. Everyone knew Mr. Sui. They all enjoyed his tales of pond life and his daring escape from captivity.  Unlike his fellow goldfish, he had retained his bright golden hue and quite literally stood out in a crowd.  This news was too close to home to be ignored.

“Use great caution little ones, “she continued, and keep your eyes to the skyworld. Do you remember the rules?”  Without further prompting all recited the blue foot rules in monotone preciseness: “August & September use caution and remember. From the skyworld keep you three feet and the blue feet you will not meet.”  A satisfied smile crawled across her face and she rolled the picture back into place.

  “Very good. Very good,” she cooed. “We’ll all get through this dangertime in good shape if you just keep your wits about you and stay deep. This will soon pass.” Resuming her chirping manner, she continued “Now, let’s get out our scale books and turn to the section on fin care.”

  From Ms. Percidae’s perspective on the bottom of the Detroit River Fish School, the blue claw is only a seasonal nuisance. From our perspective as shoreline and skyline observers the blue claw is much more than that. The blue foot in question is that belonging to the Osprey – the most efficient fisherman on our local waters.

  Ospreys, or fish eagles, begin their autumn migration while summer still lingers here in the lake shore country. Several are now nesting in S.E. Michigan and will soon become a regular part of our summer fauna as well. These large graceful predators are mostly white with a distinct brown eye stripe and dark brown back.  Their long pointed wings extend 4.5 to 6 foot across and are held bent at the wrist (a crucial identification feature).  There are many other features to explore on this bird, but since Ms. Percidae brought it up, perhaps those blue feet are the most impressive.  Take another look at the drawing (I am M. Madtom) and re-examine those incredible appendages.

  Although ospreys will take small mammals, birds and reptiles in a pinch, they are pretty much fish specialists. Their sleek talons are the largest among North American predatory birds and the rough palms provide a sure grip on slimy prey. Of course we already discussed that in the classroom earlier. What we didn’t talk about, however, are the steps taken by the bird in the moments leading up to the fish grab.

  The prey is spotted from high above as the bird slowly circles over the water surface.  Take a look at this picture and you’ll get an appreciation for the huge eyes on these pisciverous birds.  Once a fish is spotted by those jeepers peepers, ospreys have the ability to hover in place until the scaled target is pin-pointed and the calculations are made for a dive.

  The dive itself is a sight to behold. With wings tucked, the osprey plummets like a stone. At the last second before impacting the water the feet are brought forward to hit first.  The inside toe of each foot is reversible, so it can be brought back to form the foot into an “X” pattern for maximum coverage on the prey. It has been estimated that these birds hit the water at speeds up to 80 miles per hour.  The eyes and nostrils close on impact and the momentum carries the bird well below the surface where it takes hold of the fish.  Once locked on, it takes great strength to break free with labored wing beats and pull the catch up out of the water.  In flight, ospreys always re-position their prey to face head first and gingerly manipulate it while gaining altitude.

  There are several factors in favor of the fish in any potential interaction with fish eagles.  First of all, the element of depth is crucial – usually fish are taken only within three feet of the water surface (remember the blue foot code?).  Secondly, brightly colored fish are easier to spot than darker ones.  This is why Mr. Sui was targeted.  Wild lake goldfish normally turn greenish brown like their carp relatives, but some retain their bright hues and pay the price.

 The last consideration concerns accuracy.  In the world of predatory animals, their rate of success is usually pretty low.  When you see that lion chase down and tackle a gazelle on the Discovery Channel you are privy to the benefits of editing.  The feline attempted the same feat at least a dozen times before finally achieving a meal. The same is true of predatory birds.  Osprey catch vs. dive studies have shown the birds to be successful about 40% of the time -which is much higher than most. At least one study revealed a 90% accuracy rate, but that is equivalent to a no-hitter in baseball.  For the most part, the fish get away to live another day, but either way that’s quite a feat!

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