[Bristol-Birds] Re: about shallow-diving gulls

Some species of gulls, but not all, make shallow dives from the air.  This is 
sometimes for food gathering.  It is also a way of submerging for a brief bath. 
  Ring-billed Gulls are otherwise seldom, if ever, observed diving under water 
from a floating position at the surface of our lakes.

The birds at Middlebrook Lake in Bristol Tennessee are Ring-billed Gulls, as 
you pointed out.  I have watched them make these shallow dives there this week 
and the dives seem to be more prevelant on warmer and sunny days.  

I set up a spotting scope to try and determine what type of food they may be 
gathering and eating.  No birds were seen with anything in their beaks when 
they instantly surfaced.  There was no solid matter such as garbage, etc. 
floating where they dropped down. They are not under water long enough to chase 
fish or gather aquatic life of any notable size.

None looked like they were swallowing anything.  Another interesting aspect of 
the shallow dives I saw at Middlebrook Lake, revealed that this behavior was 
normally ignored by other Ring-billed Gulls which were a few hundred yards 
away.  

Rack Cross and I have spent months observing Ring-billed Gull behavor during 
winter.   We learned alot about their reaction to food and their feeding habits.

We were able to determine that if a few Ring-billed Gulls found a source of 
food on the water or land and started flying to it, most other Ring-billeds in 
sight that were the least big hungry began to fly quickly in the direction of 
the new food source.   There is a body language to the way they fly towards 
food.  

This body language behavior in European Starlings is dramatic and well 
recognized.  It is a sort of sudden steep glide with a downward twist.  This 
causes starlings from all around to           Rack with Ring-billed Gull we 
trapped &  banded.
enter a feeding glide going towards
the samdfood source.  We use this behavior observation as a key component for 
baiting and capturing starlings in winter.

Other nearby Ring-billed Gulls at Middlebrook Lake seem to not see these 
shallow dives as food gathering and only six or eight left a flock of 200 or so 
that were in the area to come towards this diviing behavior while I was 
watching this week.  This suggested to me that they either came to join in the 
bath or didn't understand the excitement.

Usually, when a small school of fish has been found at the surface, gulls will 
gather and dive at them.  You can sometimes see the gull with small fish in its 
bill.  Hooded Mergansers will quickly fly to the spot and join in the feeding 
freenzy.  None did when the apparent bathing activity was underway.

I have watched this shallow dive behavior in the middle of the day after they 
have apparently been feeding at the large landfill just over the hill.  I also 
noticed that the gulls do the shallow diving thing somewhat together in about 
the same area.  It was not going on all over the lake.  This is not unlike any 
group of birds that bathe together such as starlings, robins, etc.  Perhaps 
there is safety in numbers when one bird is going under and others are flying 
overhead.

The question was raised:  "Could this be something to do with fresh water 
verses salt water? Any one on the list every noticed a gull landing at the 
beach?"  No, it does not seem to have anything to do with their sinking more in 
fresh water when they hit than they would in saltwater which would cause them 
to float more.  

Perhaps I jump to conclusion here that anyone at the beach might be watching 
this same species.  You might watch Ring-billed Gulls in winter at the beach.  
But, remember, the Ring-billed Gulls we have here in winter are not gulls that 
would be found along the Middle Atlantic or south Atlantic beaches during the 
breeding season or when many of us visit the beach for warm-season vacation.

Many of our Ringed-billed Gulls may very well come from the upper areas of 
western Canada just north of the US and some may come from around the Great 
Lakes region to the upper Canadian Atlantic coast.  That is where their summer 
breeding range is known.  Most of them may not even qualify as a "sea" gull as 
our folk call them.  They are very inland as a species.

And that is why Rack and I captured and banded Ringed-billed Gulls.  We had 
hopes of having recapture information returned from birds recovered on their 
summer breeding grounds.  It would give us a better understanding of where our 
winter parking lot birds come.

Enjoy.

Let's go birding......

Wallace Coffey
Bristol, TN

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