Flock size estimates
Hi all--
I'm writing an article about estimating crowd sizes and I want to make
reference to what we know about the accuracy (or inaccuracy) with which the
typical human (or birder) estimates the size of bird flocks.
I remember reading a very interesting discussion of this some years ago
involving some of our top birders that I believe took place withinbin CT
Birds (may even have included photos by way of illustration), and if I
remember right, the main takeaway was that unless properly trained, we tend
to underestimate flock sizes rather drastically (by a factor of ten?).
Unfortunately, I haven’t been able to find the exchange or the sources
referenced, and am hoping that someone familiar with the current rules of
thumb in this area can respond and refresh my memory.
Thanks in advance for any time and consideration...
Best,
Tom de Boor
Northford, CT
A couple of good tools online for estimating flock sizes:
http://www.ycobirds.com/count
Allan WelbyRidgefield On Wednesday, July 23, 2025 at 01:43:42 AM EDT, Tom de Boor via CTBirds ctbirds@lists.ctbirding.org wrote:
Hi all--
I'm writing an article about estimating crowd sizes and I want to make
reference to what we know about the accuracy (or inaccuracy) with which the
typical human (or birder) estimates the size of bird flocks.
I remember reading a very interesting discussion of this some years ago
involving some of our top birders that I believe took place withinbin CT
Birds (may even have included photos by way of illustration), and if I
remember right, the main takeaway was that unless properly trained, we tend
to underestimate flock sizes rather drastically (by a factor of ten?).
Unfortunately, I haven’t been able to find the exchange or the sources
referenced, and am hoping that someone familiar with the current rules of
thumb in this area can respond and refresh my memory.
Thanks in advance for any time and consideration...
Best,
Tom de Boor
Northford, CT
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Don’t forget that our listserv archives can be searched for previous posts. I remember the discussion that Tom referred to and I searched and found several posts on the topic of flock size.
The following link will run the search if anyone is interested:
https://lists.ctbirding.org/empathy/search?q=Estimate&slist=ctbirds.lists.ctbirding.org&collapse=on
The second search result is a post from Frank Mantlik about a Sibley course on how to estimate flock size. I tried it and the course is still functional online.
Don’t forget the search function on the website; it is another useful aspect of our listserve system!
Chuck Imbergamo
CT Birds Moderator
Madison
On Jul 23, 2025, at 9:44 AM, AW via CTBirds ctbirds@lists.ctbirding.org wrote:
A couple of good tools online for estimating flock sizes:
http://www.ycobirds.com/count
Allan WelbyRidgefield On Wednesday, July 23, 2025 at 01:43:42 AM EDT, Tom de Boor via CTBirds ctbirds@lists.ctbirding.org wrote:
Hi all--
I'm writing an article about estimating crowd sizes and I want to make
reference to what we know about the accuracy (or inaccuracy) with which the
typical human (or birder) estimates the size of bird flocks.
I remember reading a very interesting discussion of this some years ago
involving some of our top birders that I believe took place withinbin CT
Birds (may even have included photos by way of illustration), and if I
remember right, the main takeaway was that unless properly trained, we tend
to underestimate flock sizes rather drastically (by a factor of ten?).
Unfortunately, I haven’t been able to find the exchange or the sources
referenced, and am hoping that someone familiar with the current rules of
thumb in this area can respond and refresh my memory.
Thanks in advance for any time and consideration...
Best,
Tom de Boor
Northford, CT
To subscribe or unsubscribe via email, send an email with just "join" or "leave" in the subject or body to: ctbirds-request@lists.ctbirding.org
CTBirds, a service of Connecticut Ornithological Association - Bringing birders together statewide. Please support COA: https://www.ctbirding.org/join-us/
CTBirds is for the discussion of birds and birding in Connecticut. For list rules and subscription information visit: https://www.ctbirding.org/birds-birding/ct-birds-email-list/
To subscribe or unsubscribe via email, send an email with just "join" or "leave" in the subject or body to: ctbirds-request@lists.ctbirding.org
CTBirds, a service of Connecticut Ornithological Association - Bringing birders together statewide. Please support COA: https://www.ctbirding.org/join-us/
CTBirds is for the discussion of birds and birding in Connecticut. For list rules and subscription information visit: https://www.ctbirding.org/birds-birding/ct-birds-email-list/
Thanks much, Chuck, AW, and Kathy! Those resources are very helpful. And
the general guidance, too, Chuck--I think my mistake was doing my searches
through gmail, where I get the mailings, rather than the website. To my
knowledge, Google has never acknowledged this, but I know for a fact from
my own experience and others that even if you're paying for the storage
space (as I am), they somewhat randomly cull your old mail when it reaches
a certain age. Had I realized how long ago Frank made those clearly very
memorable contributions to the discussion--I remember them like it was
yesterday, not 2012 and 2015!--I might have guessed that was the problem.
The 2023 result probably escaped me because I searched on "estimating flock
size," rather than just "estimate," but who knows? Anyway, thanks again! :)
Best,
Tom de Boor
Northford, CT
On Wed, Jul 23, 2025 at 1:18 PM Chuck Imbergamo imbercj@comcast.net wrote:
Don’t forget that our listserv archives can be searched for previous
posts. I remember the discussion that Tom referred to and I searched and
found several posts on the topic of flock size.
The following link will run the search if anyone is interested:
https://lists.ctbirding.org/empathy/search?q=Estimate&slist=ctbirds.lists.ctbirding.org&collapse=on
The second search result is a post from Frank Mantlik about a Sibley
course on how to estimate flock size. I tried it and the course is still
functional online.
Don’t forget the search function on the website; it is another useful
aspect of our listserve system!
Chuck Imbergamo
CT Birds Moderator
Madison
On Jul 23, 2025, at 9:44 AM, AW via CTBirds ctbirds@lists.ctbirding.org
wrote:
A couple of good tools online for estimating flock sizes:
http://www.ycobirds.com/count
Allan WelbyRidgefield On Wednesday, July 23, 2025 at 01:43:42 AM EDT,
Tom de Boor via CTBirds ctbirds@lists.ctbirding.org wrote:
Hi all--
I'm writing an article about estimating crowd sizes and I want to make
reference to what we know about the accuracy (or inaccuracy) with which the
typical human (or birder) estimates the size of bird flocks.
I remember reading a very interesting discussion of this some years ago
involving some of our top birders that I believe took place withinbin CT
Birds (may even have included photos by way of illustration), and if I
remember right, the main takeaway was that unless properly trained, we tend
to underestimate flock sizes rather drastically (by a factor of ten?).
Unfortunately, I haven’t been able to find the exchange or the sources
referenced, and am hoping that someone familiar with the current rules of
thumb in this area can respond and refresh my memory.
Thanks in advance for any time and consideration...
Best,
Tom de Boor
Northford, CT
To subscribe or unsubscribe via email, send an email with just "join" or
"leave" in the subject or body to: ctbirds-request@lists.ctbirding.org
CTBirds, a service of Connecticut Ornithological Association - Bringing
birders together statewide. Please support COA:
https://www.ctbirding.org/join-us/
CTBirds is for the discussion of birds and birding in Connecticut. For
list rules and subscription information visit:
https://www.ctbirding.org/birds-birding/ct-birds-email-list/
To subscribe or unsubscribe via email, send an email with just "join" or
"leave" in the subject or body to: ctbirds-request@lists.ctbirding.org
CTBirds, a service of Connecticut Ornithological Association - Bringing
birders together statewide. Please support COA:
https://www.ctbirding.org/join-us/
CTBirds is for the discussion of birds and birding in Connecticut. For
list rules and subscription information visit:
https://www.ctbirding.org/birds-birding/ct-birds-email-list/
Hi Tom,
A couple of years ago I was interested in a similar question — not just my own estimates, but also easy ways to count birds in a photo. You can see my discussion and results in this list, for Tree Swallows in the fall:
https://ebird.org/checklist/S150800320
I assume you've also seen David Sibley's page on this?
https://www.sibleyguides.com/courses/estimating-numbers/
And yes, my sense is that most people underestimate flock sizes by quite a lot! A factor of ten seems high, though. Just personally, I'm not surprised when I do a careful count and find that I’m off by a factor of 1.5 or 2, but it seems unlikely that I'd look at, say, that Tree Swallow swarm and only think there are a hundred or so birds there. Then again, I realize I'm the kind of person who takes online flock-size quizzes and counts a thousand dots in a photo by hand, so I'm probably not a representative human! 🙂
I'll be curious to see your final article!
Bill
From: Tom de Boor via CTBirds ctbirds@lists.ctbirding.org
Sent: Wednesday, July 23, 2025 01:42
To: ctbirds ctbirds@lists.ctbirding.org
Subject: [CT Birds] Flock size estimates
Hi all--
I'm writing an article about estimating crowd sizes and I want to make
reference to what we know about the accuracy (or inaccuracy) with which the
typical human (or birder) estimates the size of bird flocks.
I remember reading a very interesting discussion of this some years ago
involving some of our top birders that I believe took place withinbin CT
Birds (may even have included photos by way of illustration), and if I
remember right, the main takeaway was that unless properly trained, we tend
to underestimate flock sizes rather drastically (by a factor of ten?).
Unfortunately, I haven’t been able to find the exchange or the sources
referenced, and am hoping that someone familiar with the current rules of
thumb in this area can respond and refresh my memory.
Thanks in advance for any time and consideration...
Best,
Tom de Boor
Northford, CT
To subscribe or unsubscribe via email, send an email with just "join" or "leave" in the subject or body to: ctbirds-request@lists.ctbirding.org
CTBirds, a service of Connecticut Ornithological Association - Bringing birders together statewide. Please support COA: https://www.ctbirding.org/join-us/
CTBirds is for the discussion of birds and birding in Connecticut. For list rules and subscription information visit: https://www.ctbirding.org/birds-birding/ct-birds-email-list/