[texbirds] Brown vs. American White Pelican - food capture behaviors
- From: MBB22222@xxxxxxx
- To: texbirds@xxxxxxxxxxxxx
- Date: Sun, 10 Feb 2013 15:49:04 -0500 (EST)
Here is an illustration showing the Brown and American White Pelican food
capture behaviors. Some are well known some are not.
_http://www.pbase.com/mbb/image/148714457/original_
(http://www.pbase.com/mbb/image/148714457/original)
In published material we can find that both pelicans found in North
America, Brown and American White, are using only a very few techniques to
capture the food. Collected observations summarized in BNA (The Birds of North
America) species accounts show that Brown Pelicans mainly capture food by
surface plunging when after sight the prey from air they dive head-first into
water. Evidently the dive and plunge are mastered by practice and
experience so older individuals are more skillful compare to juveniles.
White American Pelicans capture food mainly by surface-seizing when float
and swim, scoop prey into pouch. Brown Pelicans, sometimes, are foraging in
similar way as well. They are a few possible actions and bill movements
during these kind of foraging but my illustration would become too âlongâ
if
I wanted to present every combination that depend also on fish
concentration, prey size, water depth and weather condition.
In general descriptions, in books and found on internet sites, it is often
noted that American White Pelicans are never foraging by surface plunging.
I think we can only generally say that as there are only two published
records documenting plunge diving in Whites both times at Pyramid Lake,
Nevada.
Both species are pirating food from other birds - in my observations Whites
doing it more often and being more vicious, usually attacking birds that
showed up on the water surface with larger fish hold in the bill. Browns are
sometimes chasing other birds which are transporting fish in air and
trying to make them drop the prey.
Both pelicans can form large flocks foraging in coordinated and cooperative
way. Whites do that very often and seem to be much better organized.
Basically above described foraging behaviors show the whole repertoire
observed and described in both species.
I do not have opportunity to observe White American Pelicans too often but
because Brown Pelican occurs in habitats I visit often I had many
opportunities to observe they foraging behaviors on many occasions.
In composite photos you can find a few more behaviors that Brown Pelicans
can use when trying to capture the food.
Surface plunging - feet-first dive. As you can see in photo Brown can dive
from flight feet-first and immediately after plunging into the water,
practically at the same moment, thrust the bill into water trying to catch the
fish into its pouch.
Jump-plunging - I adopted this term often used when describing one of the
gull foraging behaviors. Looking for prey, when floating on water, Brown
after spotting a prey nearby will make a very low, very short flight and
plunge into water.
Surface plunging from perch. Brown can stay on the perch observing water
below - after spotting the prey it will plunge into water trying to get it.
I could not stop myself from including in few photos a very smart Laughing
Gulls using pelican head or back as perch when waiting for prey to show up
near foraging pelican. Of course this has nothing to do with pelican
capturing prey and evidently does not bother some Brown Pelicans. I never saw
gull trying that with Whites. BTW if anybody saw some interesting pelican
foraging behaviors it would be great to hear about it. Wonder if anybody ever
observed Whites plunge-diving?
Mark B Bartosik
Houston, Texas
_http://www.pbase.com/mbb/from_the_field_
(http://www.pbase.com/mbb/from_the_field)
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