Wednesday, April 27, 2011

Furry mammal carnage at the nest

As the sun rose on the nest yesterday (Tuesday) we could see how productive the tiercel had been in bringing food to the nest. Carcasses of small, furry mammals - mostly baby rabbits and rats - littered the edge of the nest bowl.

Yesterday's newly hatched and bedraggled eyass #3 was now a fluffy, smaller version of its siblings.  All three look strong and active as the tiercel stands guard over their morning nap

Temperatures rose here yesterday into summer-like 80s, and instead of nestling down over the babies, the haggards stood by watchfully, lifting their wings slightly to stay cool.

When the formel settled closer, the eyasses stayed out in front of her, rather than under....

.... and soon collapsed into a sleeping pile.

As the afternoon heat intensified, we could see the haggards panting with their beaks open as they made sure the chicks were kept in the shade.

I asked John Blakeman - a master falconer and raptor biologist from Ohio who has consistently shared his enormous knowledge of hawks to help understand what we are witnessing at the nest - whether the heat would adversely affect the fragile eyasses.

John commented:

"The summer heat (in the 80s) is of absolutely no concern. Yes, the haggards are panting a bit, just like a hot pooch. This allows them to cool off. If they didn't have to be at the nest, they'd merely lift up a thousand feet or more and cool off in the cooler air aloft. But their focus is as it should be, at the nest, warm or not.

For the eyasses, the heat is wonderful. For their first 6 to 12 days out of the egg, they are poikilothermic, "cold blooded," unable to generate enough of their own body heat to stay warm. That accounts for the formel's brooding behaviors, keeping the eyasses warm under her breast feathers, when that is required. But with these warm temperatures, all is well. The three little ones are very comfortable out in the mid-day warmth.
It all looks very good for this year, with an fully-experienced pair and plenty of prey."
--John Blakeman

With an abundance of food in the nest, the Franklin hawk family is off to a fabulous start in their third year of raising chicks on the Board Room window-ledge.


  1. Lovely, and thank you JB for your input.

  2. Very interesting. I would love to ask John Blakeman a question, if I can. At two different times yesterday, I observed the two bigger eyasses tussling with each other. One, in particular, seemed quite aggressive and kept pecking at the other and knocking it down. The little one was keeping its head down and staying out of the confrontation. I assume this kind of squabbling is normal behavior? Is it possible for one eyass to seriously injure another?

  3. What you saw is quite normal. With Red-tails, it’s never of any concern. No harm will come to any of the eyasses, unless the parents fail to bring sufficient food. Then, a larger eyass can kill a smaller one, after profound hunger. That won’t happen here, by any means.

    So, just as little kids “fight,” little eyasses do a bit of this. After all, these birds are born killers. All of what you saw is normal nerve and muscle development. Just as with little children, the young eyasses have to learn how to use their muscles in coordination. Poking the bill at another sibling, even sometimes stealing a piece of food it is eating, is all normal and even helpful behavior.

    Eyass Golden Eagles do this same thing. But universally, it turns out differently. It’s called the Cain and Able Effect. Ubiquitously, the larger Golden Eagle eyass will slay the younger one. Golden Eagles most often lay two eggs, and both hatch. But the larger hatched eyass at some time before fledging will reach over and sink some talons into its brother or sister, killing it.

    Our Red-tails are much more respectful and civil!

    –John Blakeman

  4. Thanks very much for answering my question, John. I really enjoy reading your insights into the red-tail hawk behavior. And thanks to Della, too, for this blog and the great screen caps!