Sunday, January 11, 2015

Foraging Sandhill Cranes

Yesterday on a hike around the neighborhood (5 mile hike - big neighborhood) I came upon my resident pair of Sandhill Cranes busily foraging in the lawn-like vegetation adjacent to Honore Avenue.  Unlike cranes on the prairie that spook and take flight when you are 18 miles from them, these urbanized cranes have become habituatied to humans and allow very close approach as long as there are no colts around.

My pair was busily probing the ground as I walked up to them.  At first I sat on the grass 2 feet from one of them (I could hear it breathing) and watched as they probed the soil.  They were probing so quickly it was like watching Dowitchers or Stilt Sandpipers do their sewing machine-like foraging technique.  They are fast.  The birds probed with their mandibles open and very rapidly scoured the earth.  Whenever they found something they'd stop, pick it up with the very tip of their bill, and then quickly swallow it.  Curious about what they were eating I laid down on the ground so my eyes were almost at ground level with the tip of the birds mandibles and saw that they were catching ants.  Lots and lots of ants. Granted one ant isn't going to provide much nourishment but given the volume they were consuming I'm guessing they were obtaining lots of their dietary needs. 

The exoskeleton of ants is made up almost entirely of chitin which is very high in protein.  For instance the skin of shrimp is made up of chitin which is where most of the protein humans receieve from eating shrimp lies.  Another important component of ant exoskeleton is calcium carbonate.  My guess is that with the onset of nesting season the female of this crane pair was pigging out on ants to get protein for the embryo that's going to form in her egg and calcium to help create a solid shell for the egg in which the embryo will develop.  Once again, like everything else in nature, everything is connected.