Why the Cassin's Finch invasion?

[Richard Trinkner]

I'd be very interested in theories to explain this spring's dramatic Cassin's Finch invasion of the lower elevations of the Front Range.  We usually get these prolific snow storms in March and April, but my 24 years of personal records don't show anything previously like this year's Cassin's Finch invasion. (Of course, 24 years is a tiny data window for a species that probably predates humans...) 

Are cone crops in the high country poor this year? Are the finches coming from northern latitudes? Was last year a banner breeding year? Why is the weather disproportionately affecting this particular high-elevation finch species?

I don't have any answers myself, but hope that others might.

Cheers,

Richard Trinkner

Boulder

[Dave Hyde]

Here near Storm Mountain in Larimer Cty. we usually have Cassin’s finches but generally around 4 max (this over four years), until this year when there was about 30 the other day and today 8 or so. I’m thinking maybe all the snow we’ve had is sending the birds lower. I can’t remember a day in the last few months when the ground was not covered with snow. One storm after another just rolling through. Maybe the Cassin’s finches are having difficulty finding seed on the ground?

Dave Hyde/Larimer Cty.

 

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[David Tønnessen]

Cassin's Finches invaded central Colorado's Ponderosa mountains west of the Springs last fall and were still around here just a few weeks ago in huge numbers. I was birding Ponderosa Pine forests near Boulder a couple months ago and didn't have any Cassin's Finches, so I wonder if the recent invasion into Boulder is due to finally depleting most of the Ponderosa Pine crop down here.

David Tonnessen
Colorado Springs, CO

[David Tønnessen]

Building off of that, Ponderosa cones around Boulder are also stocked right now, but they may have become so at a later time than those further south, hence the masses of Cassin's Finches passing it by settling for the cones down here--until now.

[JIM THOMPSON]

First time in back yard.  Here for three days.  About 25 mostly female.  First time in yard.

JIM THOMPSON

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[JIM THOMPSON]

I shoulf have added SW Loveland.

JIM THOMPSON

[Eric DeFonso]

FWIW, on April 4 I had a solo singing Cassin's Finch at Joder Ranch which is just off US 36 between Boulder and Lyons. According to eBird, my report there was the first report of CAFI ever for that specific hotspot in the 4 years that hotspot has been around. (The trail for Joder Ranch ascended from the last edge of grassland/farmland up into ponderosa pine foothills.) Of course that was before the plethora of CAFI reports we've had in the past week or so, but in retrospect maybe I was seeing the vanguard of the invasion force.

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Eric DeFonso
near Lyons, Boulder County, CO

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[Scott]

Be careful calling them females... Juvenile male Cassin's Finches, like Purple Finches don't get their red color until the spring/summer of their second year. So some of those  that look like females may actually be juvenile males

So it is better to call them "female types"

A goo way to tell  adult female finches from juvenile (sex unknown) id to look at their tail feathers.

Adult female birds will have rounded tail feathers, and juvenile birds will have pointed tail feathers.

Best,

Scott Rashid
Estes Park

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[Sue Riffe]

Hi all,

We had 2 Cassin's during this past winter in Lyons. The low estimated of 85 Cassin's Finches have been here over the last two snow storms this week. Most winters we will have just single digits even with heavy snows.

Bonus birds this week include a pair of Evening Grosbeaks and 4 Broad-tailed Hummingbirds.

Stay healthy,

Sue Riffe

Lyons, CO

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Sue Riffe

[arvind panjabi]

I concur that this is an unusual event.  I estimated around 175 CAFIs in yard yesterday here by horsetooth mountain west do Fort Collins.  They devoured two gallons of birdseed.  This morning I estimated 105.  The most I ever had before this was probably around 30 birds.  Love having them here!

Arvind Panjabi

Larimer Co.


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[Scott Severs]

I had about 30 in SW Longmont, and loved every minute of it! Plus a few Pine Siskins.

Here's a little video I shot: https://youtu.be/FvhPuFv4EM8

Scott Severs

Longmont

On Friday, April 17, 2020 at 10:24:43 AM UTC-6, Arvind wrote:

I concur that this is an unusual event.  I estimated around 175 CAFIs in yard yesterday here by horsetooth mountain west do Fort Collins.  They devoured two gallons of birdseed.  This morning I estimated 105.  The most I ever had before this was probably around 30 birds.  Love having them here!

Arvind Panjabi

Larimer Co.


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On Friday, April 17, 2020, 7:54 AM, Sue Riffe <she...@gmail.com> wrote:

Hi all,

We had 2 Cassin's during this past winter in Lyons. The low estimated of 85 Cassin's Finches have been here over the last two snow storms this week. Most winters we will have just single digits even with heavy snows.

Bonus birds this week include a pair of Evening Grosbeaks and 4 Broad-tailed Hummingbirds.

Stay healthy,

Sue Riffe

Lyons, CO

On Thu, Apr 16, 2020 at 2:45 PM Richard Trinkner <richardi...@gmail.com> wrote:

I'd be very interested in theories to explain this spring's dramatic Cassin's Finch invasion of the lower elevations of the Front Range.  We usually get these prolific snow storms in March and April, but my 24 years of personal records don't show anything previously like this year's Cassin's Finch invasion. (Of course, 24 years is a tiny data window for a species that probably predates humans...) 

Are cone crops in the high country poor this year? Are the finches coming from northern latitudes? Was last year a banner breeding year? Why is the weather disproportionately affecting this particular high-elevation finch species?

I don't have any answers myself, but hope that others might.

Cheers,

Richard Trinkner

Boulder

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[Richard Trinkner]

I looked at the Cassin's Finch distribution map on Birds of the World, and learned that some birds winter in New Mexico and northern Mexico.  See attached range map.  I had assumed that they had been forced down from higher elevations to our west.  Maybe that's not the case. Perhaps our invading finches were on their northern migration when the storms stopped their progress. Recent discussions of the storm fronts on Cobirds suggest that the storms pushed northwards through Colorado, rather than the usual westerly direction.

Are our invaders the more southern members of the species?

Richard Trinkner

Boulder

 

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[Sally Waterhouse]

We continue to have about the same number of Cassin's (we regularly flocks of 20-30) both at the feeder and in the forest at the base of the Collegiate Peaks here in the BV-Salida area that have been present most of the winter.  The Ponderosa cone crop was/is heavy here.  So the "Boulder invasion" doesn't seem to have come from here; the idea that this was a migrant push from further south is an interesting idea.

Sally Waterhouse

Nathrop