cobirds colorado rare bird

Friday, 17 January 2025

Re: [cobirds] Yellow-billed Loons

Wonderful photo John. Thanks for sharing.

Wayne Wathen

From: 'John Maynard' via Colorado Birds <cobirds@googlegroups.com>
Sent: Friday, January 17, 2025 12:02 PM
To: cobirds@googlegroups.com <cobirds@googlegroups.com>
Subject: [cobirds] Yellow-billed Loons

There was a Yellow-billed Loon in breeding plumage at 11 Mile Reservoir October 14, 2024. Photo.

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John Maynard
Manitou Springs, CO
719-332-6279

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[cobirds] Yellow-billed Loons

Re: [cobirds] Status of Yellow-billed Loons in Colorado

The Birds of the World account for the yellow-billed loon (latest version published in 2020) includes this:

"A recent phenomenon (beginning in the 1980s) has been the accumulation of records of Yellow-billed Loons migrating and wintering well inland in North America. Although some inland sightings were questioned by Phillips (33), there have been photographically documented records for such inland areas as interior British Columbia, eastern Washington, Idaho, Montana, Minnesota, Illinois, Nevada, Utah, Colorado, Oklahoma, Arkansas, Arizona, New Mexico, and western Texas, as well as careful sight records for Missouri and elsewhere (records from North American Birds, eBird). Many of these records were from artificial reservoirs that represent new potential habitat for this species. The recent discovery of these birds, however, probably stems from new information on field identification of loons in basic plumage that has only recently become widely available."

And this:

"In general, individuals breeding in northern Alaska fly through the Bering Strait and winter off the coast of Asia, while those in central Canada fly south overland and winter off the Pacific coast of North America. Those breeding on the Seward Peninsula and in northern Canada, winter in both places."

On Fri, Jan 17, 2025 at 8:50 AM Mary Geder <mfg5000@live.com> wrote:

And then there was the June YBL at McClellan Reservoir.
Mary Geder

Jefferson Co

Sent from my iPhone

On Jan 17, 2025, at 8:47 AM, Peter Gent <gent@ucar.edu> wrote:

All,

The CBRC has 35 records of Yellow-billed Loon, which can be seen at https://cobrc.org/Reports/SpeciesDetail.aspx?id=59

There were 3 records in 2018, 3 in 2020, and 2 in 2022. There were about 5 birds in CO in late 2024, so that does seem to be an increase in the maximum number of birds in winter and well above average. These birds were seen at Pueblo Res, Cherry Creek Res, Chatfield Res, Union Res and Boyd Lake. These are places that have been well birded over many years, so this number does seem rather unusual. What was unprecedented was that a bird spent all of last summer in south Denver mostly at McClellan Res. Does this mean that the species has increased in numbers recently or is breeding further east than before? I do not know the answers to these questions.

Cheers, Peter Gent.

Chairman CBRC.

On Thu, Jan 16, 2025 at 5:17 PM Robert Righter <rorighter@earthlink.net> wrote:

Hi All

In 1992 with the publication o Colorado Birds, the Yellow-billed Loon was considered a casual fall migrant (5 records) and winter resident (4 records). According to this winter's eBird reports there has been multiple sightings, at multiple reservoirs. Something is going on with the Yellow-billed Loon. Could they be having more successful breeding in the arctic (if so why) thus significantly more YBLO are moving south in the winter? Usually there isn't just one reason to explain phenomenon, but multiply inter-connected reasons.

Anyone have any ideas!

Bob Righter
Denver, CO

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Re: [cobirds] Status of Yellow-billed Loons in Colorado

And then there was the June YBL at McClellan Reservoir.

Mary Geder

Jefferson Co

Sent from my iPhone

On Jan 17, 2025, at 8:47 AM, Peter Gent <gent@ucar.edu> wrote:

All,

The CBRC has 35 records of Yellow-billed Loon, which can be seen at https://cobrc.org/Reports/SpeciesDetail.aspx?id=59

There were 3 records in 2018, 3 in 2020, and 2 in 2022. There were about 5 birds in CO in late 2024, so that does seem to be an increase in the maximum number of birds in winter and well above average. These birds were seen at Pueblo Res, Cherry Creek Res, Chatfield Res, Union Res and Boyd Lake. These are places that have been well birded over many years, so this number does seem rather unusual. What was unprecedented was that a bird spent all of last summer in south Denver mostly at McClellan Res. Does this mean that the species has increased in numbers recently or is breeding further east than before? I do not know the answers to these questions.

Cheers, Peter Gent.

Chairman CBRC.

On Thu, Jan 16, 2025 at 5:17 PM Robert Righter <rorighter@earthlink.net> wrote:

Hi All

In 1992 with the publication o Colorado Birds, the Yellow-billed Loon was considered a casual fall migrant (5 records) and winter resident (4 records). According to this winter's eBird reports there has been multiple sightings, at multiple reservoirs. Something is going on with the Yellow-billed Loon. Could they be having more successful breeding in the arctic (if so why) thus significantly more YBLO are moving south in the winter? Usually there isn't just one reason to explain phenomenon, but multiply inter-connected reasons.

Anyone have any ideas!

Bob Righter
Denver, CO

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Re: [cobirds] Status of Yellow-billed Loons in Colorado

All,

The CBRC has 35 records of Yellow-billed Loon, which can be seen at https://cobrc.org/Reports/SpeciesDetail.aspx?id=59

There were 3 records in 2018, 3 in 2020, and 2 in 2022. There were about 5 birds in CO in late 2024, so that does seem to be an increase in the maximum number of birds in winter and well above average. These birds were seen at Pueblo Res, Cherry Creek Res, Chatfield Res, Union Res and Boyd Lake. These are places that have been well birded over many years, so this number does seem rather unusual. What was unprecedented was that a bird spent all of last summer in south Denver mostly at McClellan Res. Does this mean that the species has increased in numbers recently or is breeding further east than before? I do not know the answers to these questions.

Cheers, Peter Gent.

Chairman CBRC.

On Thu, Jan 16, 2025 at 5:17 PM Robert Righter <rorighter@earthlink.net> wrote:

Hi All

In 1992 with the publication o Colorado Birds, the Yellow-billed Loon was considered a casual fall migrant (5 records) and winter resident (4 records). According to this winter's eBird reports there has been multiple sightings, at multiple reservoirs. Something is going on with the Yellow-billed Loon. Could they be having more successful breeding in the arctic (if so why) thus significantly more YBLO are moving south in the winter? Usually there isn't just one reason to explain phenomenon, but multiply inter-connected reasons.

Anyone have any ideas!

Bob Righter
Denver, CO

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Thursday, 16 January 2025

Re: [cobirds] Status of Yellow-billed Loons in Colorado

I agree there are often multiple reasons contributing to phenomena. I'll add another possibility. Many of the large reservoirs in the Front Range and across the west aren't that old (1900s on with some larger ones completed more recently (Cherry Creek completed in 1950, Chatfield and Lake Pueblo completed in 1975, for example). It is possible that yellow-billed loons are adapting to these as migration stopovers and wintering areas.

There is a famous example (to ornithologists at least) of European blackcaps changing their migration routes and overwintering areas within decades published by Berthold, et. al. in a 1992 paper in Nature: "Rapid microevolution of migratory behavior in a wild bird species." I've pasted the abstract below. Caveat, I don't know if subsequent studies supported this paper or whether other examples have been found and published.

I wonder whether data on common loons occurences in the Front Range show the same pattern?

************************************************************************************************************************************************************************************************************************

"THE Blackcap, Sylvia atricapilla, a widespread Palearctic migratory bird, rarely wintered in Britain until the 1950s. The winter population has since increased to several thousand birds1,2. Ringing indicates that these are not British Blackcaps forestalling migration, but birds breeding in Continental Europe reaching Britain on a novel westerly migration route3,4. The proportion of north-western migrants among Blackcaps ringed in parts of Germany and Austria has increased from 0% before 1960 to currently 7-10%5-7. We bred British wintering Blackcaps in captivity and determined the migratory direction of their offspring. Here we report that these birds migrate west-northwest in autumn, a direction genetically distinct from the British breeding population and the predominantly southwestern migratory population of west-central Europe. The novel route must have evolved within the past 30 years with selection favouring birds wintering some 1,500 km further north than most of their conspecifics. To our knowledge, this is the first case in any vertebrate in which a drastic and recent evolutionary change of behaviour has been documented and its genetic basis established."

On Thu, Jan 16, 2025 at 5:31 PM Todd Deininger <goldeneagle90a@gmail.com> wrote:

There seems to have been a push of YBLO inland through the NW this fall/winter. CO, UT, WY, MT, ID, TX had sightings. Weather?

On Thu, Jan 16, 2025, 5:17 PM Robert Righter <rorighter@earthlink.net> wrote:
Hi All

In 1992 with the publication o Colorado Birds, the Yellow-billed Loon was considered a casual fall migrant (5 records) and winter resident (4 records). According to this winter's eBird reports there has been multiple sightings, at multiple reservoirs. Something is going on with the Yellow-billed Loon. Could they be having more successful breeding in the arctic (if so why) thus significantly more YBLO are moving south in the winter? Usually there isn't just one reason to explain phenomenon, but multiply inter-connected reasons.

Anyone have any ideas!

Bob Righter
Denver, CO

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Re: [cobirds] Status of Yellow-billed Loons in Colorado

There was a bomb cyclone off the coast of Oregon and Washington in early November (3rd/4th). I wonder if migrating birds were pushed inland by that storm? I don't have the first date they showed up in Colorado, but the timing seems close.

Kristin Tallis

On Thu, Jan 16, 2025 at 5:31 PM Todd Deininger <goldeneagle90a@gmail.com> wrote:

There seems to have been a push of YBLO inland through the NW this fall/winter. CO, UT, WY, MT, ID, TX had sightings. Weather?

On Thu, Jan 16, 2025, 5:17 PM Robert Righter <rorighter@earthlink.net> wrote:
Hi All

In 1992 with the publication o Colorado Birds, the Yellow-billed Loon was considered a casual fall migrant (5 records) and winter resident (4 records). According to this winter's eBird reports there has been multiple sightings, at multiple reservoirs. Something is going on with the Yellow-billed Loon. Could they be having more successful breeding in the arctic (if so why) thus significantly more YBLO are moving south in the winter? Usually there isn't just one reason to explain phenomenon, but multiply inter-connected reasons.

Anyone have any ideas!

Bob Righter
Denver, CO

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