The Gull BIlled Tern Enigma

Gull Billed Tern; Beak in Sand

Gull Billed Tern; With Crab

Nature.....a complete enigma at times. I have been birding for near 30 years and although not nearly the expert as those found around the Cape May parts...I like to think I have 'above average' birding knowledge. But as always, part of that knowledge gain comes at a price, or I should say a gift...a true gift...is when I have the time to simply observe birds, simply to observe and to gain that knowledge.

Too many times we are on an 'Audubon walk' or a 'field trip' or just a casual walk-about...with nothing in particular in mind for  we are out to see what we can see. But next time, take this challenge.....go out and with no pretense in mind, find one species and dwell on that species only. Learn from it, observe it.  I was just doing the usual this past walk-about....out looking for any-old bird and came across a Gull-Billed Tern (Originally called Marsh Tern by Bent in 1921). I decided to focus on this one bird and ended up with a few shots yet more importantly; questions. Slow down I tell myself......observe nature, watch wildlife., question nature...always question...brave the gnats and flies and while they are quite content on forming a bug halo around your head, just give them no bother. Take the time to observe. Slow down time, forget what else is to be had.....observe. 

Now...this Gull-billed Tern is found on all continents with the exception of our southern snow exposures one. This Tern differs in that while they have a preference for salt water marshes and habitat similar to other Terns, these Terns do not dive into the water but rather prefer mudflats for their food source. Look at the close-up shots below which merely mirrors the full sized ones above....the left one has the Tern fully placing it's  beak into the sand. You have to turn your head to grasp  this view.  The black portion is the cap/top of the Tern's head with beak encased in the sand. The second shot on the right has lead to 'success' as a crab has been plucked from the mudflat.  

Now....focus on the shot on the left. You can see the Tern has glided down from flight and forced it's beak up to it's eye's into the sand. This is all done in one continuous movement as it glides down in flight and as quickly as my lens can capture its 'in flight' glide down, the next frame shows the beak in the sand. Instantaneously and my camera shoots 7-8 frames per second.  While still moving and in flight....it snatches the crab embedded in the sand and flies off as evident by the second close up of the crab grasped tightly within the beak. There is no hovering....in fact I have no idea how the Tern even knows a crab is buried underneath the sand..yet the returns are greater that those on Wall Street as of late....See shot below as it rises with crab in beak. 

The mystery is....how does a bird in flight....know that a crab is mucking and buried in the mud?  I know how Robins find worms.....but they are on land themselves. I know how other Terns such as our Forster's Tern who can hover above the water and see prey near the water's rise. But IN THE mudflat? 

I can see if the mudskipper or small crab is a top the mud as eye sight would come into play. But how does it know when 'the same' is below the mudflat line and hidden from sight? I have no  idea and research does not offer any help nor does it address that issue. Past research will look at how Gull-Billed Terns might steal food from Common Terns (Sibley, 2000), or swoops down to pick small crabs, spiders, and even larger prey such as lizards (Parnell, 1995) from the mudflat, but no one addresses how they can determine food which is buried within the sand as evident by the the images included in this blog. A complete enigma as I stated a bit earlier.