Friday, April 27, 2018

April 25: Eating is a noisy business

Great Blue Herons

Great Blue Heron chicks have a big job.  They must learn to eat, they must learn to fly and they must learn to fish for meals.   How do they learn?   I've some ideas (more like speculation) drawn from my watching them for the past 5 months.

In the video,  watch her neck.  It seems like she is trying to regurgitate a fish (how it gets to her bill is a mystery to me).  She opens her mouth, as if trying to regurgitate, swallows some and all the while, the chick is grabbing her bill and trying to bring it down to the floor of the nest.  Finally, she succeeds in regurgitating the fish and the 2 chick smakes crazy noises as they fight over the fish.

It seems that flying is an exercise of balancing on air.  The chicks first venture out on a limb and use their wings to stabilize themselves.  Next, is wing assisted jumping.  Below is a sequence of images showing the chick hopping to another limb and releasing their grasp on a limb.  Almost flying

Initiating a wing assisted hop.  Grasping a limb to launch from

Releasing grasp and flying (sort of STOL)

In STOL (short takeoff and landing) flight

Alighting on another limb (can't see her grasp)

Learning to eat:  Grabbing mom's bill to encourage a fresh fish to emerge

Chick (right) grabbing mom's (left) bill

Chick (right) grabbing mom's (left) bill

I think mom is trying to move the fish up her neck.  In video she looks to be choking - a prelude to regurgitation

Continuation of the bill biting

 I think what is happening is that mom is regurgitating a fish onto the floor of the nest.  The chick sees this and make a huge noise trying to eat it (see above video).   I think the chick is learning to see a small fish so that when he/she is wading, it will recognize it and try to grab it.
Aggressive bill biting.

No comments: