Bocas Valle de Agua Hawkwatch numbers

[Paul Meadow]

Hi,

Did you all see the email to the Wings and Wisdom dist list about the hawkwatch site in Panama?  I took a look at the data page out of curiosity, and I feel like I must be reading it wrong?  https://www.hawkcount.org/month_summary.php?rsite=944&ryear=2025&rmonth=10

For example, on October 8, they counted 584K+ Broad winged hawks in 10 hours!?!  That maps out to ~ 973 per minute, so how could you actually count even one species at that rate, and also count other species?  The same day they counted 15k+ TV's and 2k+ Mississippi kites.  2.2M+ Broadies in October.

Panama is a pretty narrow choke point - so funneling lots of birds.  I guess you are just making mass estimates as huge flocks pass overhead?  That would be amazing, but also no intimacy with any one bird like we have....

Any thoughts?

Best

-Paul

[Brian O'Laughlin]

Superb question! 

"they have a system" I was told when asking that same question. Not a satisfying answer. 

I'm seeing what I can find of value...

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[John Farnsworth]

There’s a system called a “blocking method” where you figure out the size of a block where you can reliably quantify the number of birds—25 is commonly used—and then you count blocks within the flocks. Usually best to use a hand clicker either to count blocks or maybe hundreds.  

When I was over at Cape May Bird Observatory about a month ago, I spent a couple afternoons out at their SeaWatch, and they were using that sort of a system.  One day they had more than 8,000 scoters fly by.  The day before they counted 1,400 white ibis.  

We commonly get flocks of 10,000 snow geese up here in Skagit County this time of year. I’ll start with blocks of 25 for two or three hundred, and then switch to blocks of 100.  It’s not easy—I can’t use binoculars when I do it.  

Working with a partner from WDFW last January, we counted all the swans in Skagit County in one day, but did it without using the block method. One bird at a time, and we counted more than 10,000 birds.  But most of them were foraging in agricultural fields.  I was working with a WDFW wildlife biologist, and we’d both count the number of birds in a field, and then add our counts together and divide by two.  It was mind-numbing. 

Here’s guidance from the US Fish & Wildlife Service on estimating flock size:  https://apps.fws.gov/aerial/estimating-flock-size#:~:text=One%20technique%20that%20is%20often,%22units%22%20within%20the%20flock.

The most important point on that webpage is “This takes considerable practice to get good at it.”  There’s a link at the bottom to test your counting skills. 

If you want to get some good practice, sign up for the South Marin County Christmas Bird Count and volunteer to help count grebes in Bonita Cove.  You’ll need a scope to do it, and the good think is that they lump Clark’s grebes together with Westerns.  But I’ve counted thousands in past years. You’ll have grebe dreams for a few nights after that one. 

John S. Farnsworth, PhD
Reading Nature: The Evolution of American Nature Writing

Nature Beyond Solitude: Notes from the Field
Coves of Departure: Field Notes from the Sea of Cortes

[Jennifer Miller]

Wow! I loved the question and answer!

That was so cool! Thank you, John.

Why does the West Coast migration have so, comparably, fewer birds? I get this vision similar to the monarchs, where’s there’s this split. Is it the mountain divide that diverts them?

- Jennifer 

On Nov 2, 2025, at 3:15 PM, 'John Farnsworth' via Hawkwatch Sat II <hawkwat...@googlegroups.com> wrote:

There’s a system called a “blocking method” where you figure out the size of a block where you can reliably quantify the number of birds—25 is commonly used—and then you count blocks within the flocks. Usually best to use a hand clicker either to count blocks or maybe hundreds.  

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[Mary Malec]

All of the major migration routes converge in Central America.  Migrants from eastern Canada and eastern US travel down the Eastern Flyway, cross the Gulf of Mexico and into Yucatan then along the coast. Migrants from the Central Flyway go directly south. Migrants from the Pacific Flyway follow the coast to Central America.

They converge--hence the great numbers

Mary

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[John Farnsworth]

It’s actually the Gulf Current.  On the east coast, warm water out of the Gulf of Mexico is moving north.  On the west coast , cold water out of the Gulf of Alaska is moving south. At my latitude (49ish) we don’t have any monarch butterflies west of the North Cascades.  I discovered this when we first moved here and I tried to purchase some milkweed plants to help conserve monarchs.  None for sale in Skagit County.  They don’t grow here. 

They may have more warblers on the Atlantic flyway, but the coolest birds are over here. 

John S. Farnsworth, PhD
Reading Nature: The Evolution of American Nature Writing

Nature Beyond Solitude: Notes from the Field
Coves of Departure: Field Notes from the Sea of Cortes

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[Paul Meadow]

Thanks everyone!  But still 100,000+ per day!  Holy moley!

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