```Dana,

That is fascinating! Thank you very much.  Now I have another birding skill to
practice!

Sharon Tierra, Brookline
Windham County

Dana Rohleder wrote:

> Sharon.
>
> You basically have to train yourself. The way I did it was counting
> waterfowl, probably the easiest because they sit fairly still. If you are
> looking at a small group of birds, say under 20, count them. If you see
> another group, guess how many are there, then count them and see how close
> you were. Every time you see a small group of anything, guess the size,
> count, then adjust your mental picture of 20 items. Eventually, you will get
> pretty good at estimating groups of 10, then 20. If you are looking at a
> larger group, try to figure how many sets of 20 are in it, then cont them
> and check for accuracy. Do this for a while until you are fairly good at
> estimating 50. Then when you see a larger group, guess how many groups of 50
> are in it. Then work on estimating 100. Once you get 100 down, you can
> handle most any flocks you will find by estimating the number of groups of
> 100 within the flock. When counting Snow Geese, good luck!! What I usually
> do is estimate an area that contains about 100 birds, then extrapolate that
> area over the area of the entire flock, and estimate how many squares and
> the area that would contain 1000 birds, then count how many groups of 1000
> are there.
>
> Everyone has a different ability to estimate numbers - it just takes
> practice - and don't be afraid to be wrong. You will almost always be
> wrong - the key is to be close and consistent. If you can estimate
> consistently within +/- 10%, you will be better than most.
>
> Dana C. Rohleder, O.D.
> Port Kent, NY