Saturday, February 2, 2019

Stringfellow

Oil on Panel, 4 x 4 inches

Wood Storks are considered colonial-nesting wading birds, which means they gather in large numbers when nesting and get most, if not all, of their food from the water. In the mid 1970s, a study was conducted in the Everglades National Park to determine the exact diet of these birds.
So, how does one go about collecting the contents of a Wood Stork's stomach? In order to obtain food eaten by storks, a team of scientists used two different methods. One was to simply handle nestling storks. I use the word ‘simply’ in sarcasm because I can’t imagine there was anything simple about it. In any event, similar to other wading birds, Wood Storks will regurgitate their food when being handled by humans. How convenient for the handler. For the storks, I’m guessing they would’ve rather kept their meals. Anyway, this method probably wasn’t the most practical or efficient depending on how large the sample size needed to be. Perhaps that is why there was a second method.
Using a helicopter as a giant beast descending from the skies above, the pilot hovered over a colony of storks while they were feeding, got really close (as close as 3-10 meters above the storks), then waited for a flight response. The storks started running, threw up their food, and flew off. Traps collected the samples that fell into the water. I felt a little stunned when I read about this method wondering if there wasn’t a better way.
But what about their diet? Wood Storks mainly consume fish, although the type of fish differs slightly depending on the season and location. They probe and chomp their way through shallow, brackish waters with a wicked bill-snap that's one of the fastest reflex actions among vertebrates. Typically, storks forage with their bills open, and as soon as suitable prey touches the bill, it snaps shut. Gulp. Prey gets swallowed whole. Yet, without even seeing their prey, it turns out storks are picky eaters. 
The Everglades storks’ diet contained a buffet of 27 different species of fish from over 3,000 prey items collected. However, only five prey comprised of 85% of the total number. Flagfish, sailfin mollies, marsh killifish, yellow bullhead, and several species of sunfish all fit the bill. (ha, get it?) Can you imagine how stinky this research had to be? And if that doesn’t get you, how about sifting and counting through platefuls of regurgitated fish? Now that’s work I’m happy to leave to the experts and read about in their research papers.


Reference:
Ogden, John C.; Kushlan, James A.; Tilmant, James T. (1976). "Prey selectivity by the wood stork" The Condor 78(3): 324-330.


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