I know there are a variety of techniques, especially where numbers get
into the high thousands and tens of thousands. And of course there are
techniques involving instrumentation, airplanes, etc.
My technique around here is to first see if the birds are in different
areas (bays, on-ice off-ice, trees, fields, ponds ... depending on
species). That way I can count each sub-area separately. I then count
individuals in areas where the numbers appear to be 100 or less. Where
the sub-areas have more than 100 birds I practice counting groups of
ten, then count by tens through the mass of birds (I've tried groups of
25 but it doesn't work for me).
I always count at least twice; when sweeping an area if the first sweep
is right to left, then the second will be left to right. I prefer to
make at least three counts, and sometimes do four. I prefer to use a
scope rather than binocs for large numbers, because I can count a
"scope-full" then reposition and count the next "scope-full."
When the birds are moving around a lot on water or in a field it gets
harder, so I try to sweep with larger numbers of birds in the scope and
follow the direction of movement with the scope. If they are moving
randomly in the scope it isn't hard to count by tens. Closely packed
birds, such as Ring-billed Gulls on the ice hunkered down and seen at
quite some distance are particularly hard to count with accuracy. If
birds are constantly coming and going I try to count the number on the
ground at any point in time, then do the in-flight birds. It is really
helpful if a large mass of birds (perhaps gulls or scaup) which are all
on the ground suddenly fly up, because then they can be counted on the
ground and in the air for comparisons.
With birds in the air my techniques begin with can I count by 5's, 10's
or 100's? Migrants or birds moving to a new field, tree, evening roost,
etc. are fairly easy because they are streaming in smaller groups which
are fairly easy to count as individuals or groups of 10 (or sometimes
groups of 100). Large numbers of birds milling about, such as at a
compost facility, are really tough and are more easily done by taking
photographs and counting the birds in the images. Often for in-air
birds I divide the flock in half visually (sometimes with my
outstretched hand), and then in half again, and so on until I get to 100
birds, or 20 birds, or 10 birds depending on the flock. Multiplication
then gives the number.
I've taken pictures of birds in flight, in trees, etc. then counted them
after the fact. One of the main reasons is to calibrate my eye for
those instances where things happen so quickly estimates are necessary.
This has worked really well for birds like Starlings, gulls, Bohemian
Waxwings, etc. I recently took a picture of a group of Starlings in a
tree at the corner of Little Chicago Road and Walker Road in Ferrisburg,
then counted the birds at home. I, by individual birds, counted 1064
birds in the image, and certainly missed some that were hidden from
view. People I've shown the picture to always estimate far fewer.
Of course it always helps to have another person independently counting
as well, and then compare counts!
Hope this help to answer your question. It would be fun to hear from
others about their techniques.
On 3/16/2011 10:31 PM, Ruth Stewart wrote:
> How in the world does one count 1600 birds?!
> ruth stewart
> e dorset
>>> Roy Pilcher and I have been conversing about the possible Barrow's
>> Goldeneye female that is constant company of the male. Thanks to a good
>> silhouette in a picture taken by Roy we are now reasonably well
>> convinced that it is indeed a Barrow's.
>> I had occasion, while giving a flight lesson, to overfly the location on
>> Sunday. From that perspective the vast majority of the birds are
>> clearly on the Vermont side of the lake .... It is difficult to judge
>> the location of the state line when viewing from Route 125.
>> My list is below.
>> Location: Champlain Bridge
>> Observation date: 3/16/11
>> Notes: Janet Nelson joined me for a while.
>> Number of species: 19
>> Canada Goose 11
>> Wood Duck 2
>> American Black Duck 21
>> Mallard 62
>> Ring-necked Duck 9
>> Greater Scaup 5
>> Lesser Scaup 9
>> Bufflehead 8
>> Common Goldeneye 112
>> Barrow's Goldeneye 2
>> Hooded Merganser 2
>> Common Merganser 1680
>> Double-crested Cormorant 4
>> Bald Eagle 1
>> Ring-billed Gull 16
>> Herring Gull 3
>> Great Black-backed Gull 1
>> American Crow 9
>> American Tree Sparrow 2
>> This report was generated automatically by eBird v2(http://ebird.org/vt)