I'll try to not make a habit of this, but here's another exchange from the
CompuServe Birding forum that involves local bird behavior. Maybe folks here
will have more answers. First, my message, followed by a most interesting
response from Joe DiCostanzo, and ornithologist in N.Y.

(******************* my message ***********************************)

OK, somebody explain this to me. All day today, outside my office windows,
Robins and Song Sparrows have been flycatching!! Yes, Robins!!, launching
themselves from the ground, or from tree limbs, catching (something) out of the
air. Now, flycatching must be a very inefficient feeding method for fat old
Robins, and nature keeps birds from inefficient practices. So there must be
~something~ about the bugs in the air that these birds really like. We always
have plenty of bugs in the air - not like NJ though <G>. But, today I have
noticed a couple flying ants on the windows. Do you suppose there's something
unique about flying ants that would drive Robins and Song Sparrows to such
behavior? (I did spot one Robin with something black in his bill)

WOOOOPS!!! Add Spooted Towhees to that list! One is doing it as I type...

Jerry - Silverdale, WA

(****************** from Joe D., NY ********************************)

Jerry,

I don't know if there is something particularly scrumptious tasting about flying
ants or if birds just can't resist going after this suddenly abundant food
source when an ant hatch occurs but robins and Song Sparrows and Spotted Towhees
aren't the only ones that do it. Out on Great Gull Island there is almost
always at least one hatch of flying ants a summer. If you think seeing "fat
old" robins flycatching is something, you ought to see the major part of a tern
colony flying around snatching ants out of the air! We always know when one of
these hatches has occurred because of the behavior of the terns. Naturally,
there are always some birds flying around over the island during the nesting
season but large numbers at once usually only coincides with some disturbance
(workers in the colony, gull or other predator in or over the colony, etc.).
These disturbances are always accompanied with lots of alarm
calls and noise from the terns. When the terns are hawking ants however, large
numbers will be flying over head in silence. Their flying is also fairly
distinctive at this time with lots of sudden stalls to grab an insect out of the
air. These ant hatches usually happen in late-July or early-August when there
are numbers of post-breeding Laughing Gulls around and they always join in the
feasting.

Now I find it very hard to believe that the terns and gulls are getting enough
return on the energy invested in catching these ants to make it worth while, but
they certainly do it year after year (usually it only happens once a summer).
It is watching behaviors such as this that have always made be very suspicous of
these nice, neat bioenergetics theories that explain all bird feeding behaviors.
I think there are times that the birds are just presented with a bunch of food
and they go after it whether it makes energetic sense or
not. I agree that if this was a regular occurrence evolution would provide some
mechanism to work against it but if it is an occurrence that happens relatively
infrequently, why would it even be noticed from a behavioral evolutionary
standpoint?

Joe

(***************************************)

OK Tweeters, is there some chemical in ants that drives birds to such excess? Is
it related to "anting" behavior? (The birds were eating the critters, not
rubbing themselves with them.) Are ants Twinkees for birds?

Jerry


E-mail from: Jerry Blinn, 03-Jun-1996