In a message dated 96-01-08 02:12:50 EST, Michael Price writes:

>
>*It is the Lost Lagoon flock of LESC (Lesser Scaup) that have taught me the
value of
>actually counting over that of simply making an eyeball estimation. To test
>how much I'm usually out, I would do the latter on this flock *before*
>counting them, and usually arrive at an approximate figure of 1,500--2,000
>birds. When I actually counted, my estimation was invariably 50% too low,
>and that turned out to be consistent whether shorebirds, ducks, crows,
>whatever, and judging by published reports over the years of Lost Lagoon
>LESC wintering flocks of 750-2,000, I'd guess I wasn't the only one who
>consistently lowballed like this. The above approximation for the large
>LESC flock is based on my experience of counting them twice a month last
>winter (aieee, not again).
>

Actually counting individual ducks in a good *managable* raft I can attest is
an excellent way to improve your skills at accurately estimating numbers. I
do the exact same thing and have gotten much better at it over the years. I
can remember invariably underestimating eyeball estimates by exactly 50%. I
did precisely the same thing as you yesterday (07Jan) with two large rafts of
western grebes on Penn Cove, Whidbey Island. Initially, it looked to me like
there were ~800 and ~1200. In fact, the actually count revealed ~1100 in one
and ~1400 in the second.

During my last two Spring field assignments at Point Piedras Blancas, San
Luis Obispo Co., California, monitoring northbound gray whale cow/calf
migration, I maintained an ancillary project counting migrating seabirds,
loons in particular. When Pacific loons are streaming past the Point in
mid-April, it is an awesome spectacle. Sometimes 40,000 per day! I count
them with a hand clicker, counting them individually (pairs is easier, 2, 4,
6, 8, 10, click) and clicking once at 10. I record my running sub-totals
every 30 minutes. I use three hand counters, one each for Pacific,
red-throated, and common loons. No, I don't need one for yellow-billeds; I
just record them individually.

We also use a Vietnam war vintage military heat sensor set up on tripod and
permanently fixed pointing out over the ocean to monitor and sub-sample gray
migration at night. It's about the size of a video camera and hooked up to a
VCR with a timer. Data recorded on tapes can be reviewed and analysed later.
Data is recorded in black and white, and anything *hot* shows up as white.
Whale blows are incredibly obvious as far as 3 miles. Much to my amazement,
birds are too!

Data recorded on tape allowed me to compare my visual counts to the real
number caught on tape which is virtually all of them. A memorable session
recorded on 23 April 1994 coincided with a massive flight of Pacific loons
during which I visually counted 12,430, most of which passed in the last
20-minutes of one 30-minute period. Obviously, I couldn't handle birds
individually or even in pairs. More like 10's and briefly 100's. It took me
24 hours to review just that section of tape counting each individual. My
visual count was off (short) by only about 500! I thought that was pretty
good!! Analysis of other tapes showed that my visual counts were right on
target, whether they be loons, brant, or surf scoters -- the big three there,
and lended me very high confidence in my ability. Phalaropes which can occur
in huge numbers are too small to be detectable with the heat sensor.

The loon migration is strictly a daylight event. There are virtually no
birds what-so-ever moving during the hours of darkness, other than occasional
gulls and most of those on nights with good moonlight. Likewise scoters and
brant.

It certainly helps to have birds either sitting still or all flying in the
same direction. When seabirds, shorebirds, gulls, blackbirds, or whatever,
are all up and flying around in circles, swarming, and mixed going in all
directions, estimating becomes truely daunting and I suspect that in these
cases, it could be easy to way over-estimate numbers. I have no solution for
testing situations such as these.

Viewing that amazing tape is nothing short of mesmerizing. I've shown it for
the the local Seattle WOS group and at the WOS convention in Spokane last
June.

Richard A. Rowlett <pagodroma at aol.com>
Bellevue, WA, USA