As you know and have no doubt done yourselves, since the first failure of Pale Male and Lola's nest three seasons ago, we have sliced, diced, and discussed to death just what may have been going wrong. With each ensuing year as depression and a feeling of helplessness ensued, various theories have been expounded and various fixes from major overhauls to minor tweaks have been thrown into the pot. From the first, John Blakeman intuitively felt it was something to do with the spikes in the bowl and here is his email and graphic explaining his very good theory to the rest of us. Testing the theory would be minor and non-intrusive compared with other fixes that have been brought forward.
On the attached drawing, where I've pasted some cradle and nest photos on my CAD program, I've shown the now-known height of the spikes with a red line. On the lower two frontal shots of the nest, I've drawn a white, egg-sized ellipse, situated at the hawk's feet.
Drawing A was the one photo I recalled, but couldn't find anywhere. Donna found it and sent it to me. It's the revelatory Rosetta Stone. It's very clear that the top of the spikes extend at least as high as tips of the thick metal bars that extend out over the front edge. I've drawn a red line showing the spike tip elevation. The location (the red line) is conservative. Notice that the tips extend slightly above the drawn line.
Drawings B and C indicate the spike tips, again with a red line. The location of an egg is shown with the white ellipse. I've placed it on the hidden surface upon which the hawk's feet are standing. This, too, is conservative. The egg-bearing surface may be an inch or so lower, bringing the egg even further down onto the pigeon spike tips, especially if the hawk happens here to be standing on the higher rim of the nest at the back, not in the lower central bowl.
For me, there is no doubt that the eggs rested directly on spike tips, thereby restricting proper rotation and allowing the cold metal spikes to conduct heat away from the warm eggs in March.
In the pre-cradle nests, the eggs might have also rested on the spikes, but they were fully enclosed with insulating nest lining all the way down to the cornice surface. Much less heat could have been wicked way as none of the spikes' surface then was directly exposed to the late winter air. With the cradle, cold air continuously surrounds the open metal base of the elevated cradle and the attached pigeon spikes. Any conducted heat easily escapes downward along the spikes, through the insulating nest lining, out to the cold air beneath. A reduction of just one or two degrees (eggs are incubated at about 100 degrees F) will kill the young embryo.
That's it. I rest my case.
Sincerely,
Drawing A was the one photo I recalled, but couldn't find anywhere. Donna found it and sent it to me. It's the revelatory Rosetta Stone. It's very clear that the top of the spikes extend at least as high as tips of the thick metal bars that extend out over the front edge. I've drawn a red line showing the spike tip elevation. The location (the red line) is conservative. Notice that the tips extend slightly above the drawn line.
Drawings B and C indicate the spike tips, again with a red line. The location of an egg is shown with the white ellipse. I've placed it on the hidden surface upon which the hawk's feet are standing. This, too, is conservative. The egg-bearing surface may be an inch or so lower, bringing the egg even further down onto the pigeon spike tips, especially if the hawk happens here to be standing on the higher rim of the nest at the back, not in the lower central bowl.
For me, there is no doubt that the eggs rested directly on spike tips, thereby restricting proper rotation and allowing the cold metal spikes to conduct heat away from the warm eggs in March.
In the pre-cradle nests, the eggs might have also rested on the spikes, but they were fully enclosed with insulating nest lining all the way down to the cornice surface. Much less heat could have been wicked way as none of the spikes' surface then was directly exposed to the late winter air. With the cradle, cold air continuously surrounds the open metal base of the elevated cradle and the attached pigeon spikes. Any conducted heat easily escapes downward along the spikes, through the insulating nest lining, out to the cold air beneath. A reduction of just one or two degrees (eggs are incubated at about 100 degrees F) will kill the young embryo.
That's it. I rest my case.
Sincerely,
John A. Blakeman
Those building and approving the carriage never thought about this as they'd never built a carriage for a Red-tail Hawk nest before. To my knowledge, no one in the world had built one so there was no prototype that had been tested previously to get the "bugs" out.
This is the prototype. So we may need to try and fix a few bugs as per usual with the first of anything.
Therefore, what to do to get this particular "bug" out? A ten minute job. Sometime before next hawk season, the spikes in the bowl of the nest, need to be clipped off. That's it. Thereby getting rid of the contact with all that metal in the carriage that is siphoning heat away from the eggs.
There we are.
Donegal Browne
Hermoine is too cute! I can't wait to show you pics of and Owl and some birds that I don't what they are.
ReplyDeleteMarian