Date: 1/18/25 9:48 am From: Timothy Barksdale <timothy.barksdale...> Subject: Re: [cobirds] Status of Yellow-billed Loons in Colorado
Co Birders:
Beginning in 1990, a Yellow-billed Loon was found wintering at Table Rock
Lake in Missouri. This bird returned for 6 years. During this period of
time we began to realize the extent of "short-stopping" of Common Loon as
well. In several of those winters, over 90 Common Loons were found . The
regular presence of wintering Red-throated and Pacific Loons ( while not
necessarily annual) began to be recorded.
In the last few years, the reservoir at Stockton has held up to 300
wintering Common Loons at a time. (!) Red-throated and Pacific are
increasingly documented. Yellow-billed has been found more regularly but is
still the more rare of the 4 species.
Missouri's birding community has dramatically expanded during this period.
Optics and cameras have improved and come down in price. Birders also have
created a demand for better knowledge. eBird has answered in some ways.
Because we can not control all the variables, it is unlikely whether we
will be able to answer whether the increase in birding has uncovered ,
historically speaking, what was always occurring, or whether there is a
real increase in continental interior records. Moving forward, however, the
steady coverage of many of these reservoirs can help to monitor populations
and determine patterns -assuming water / moisture and rainfall patterns
remain the same.
I was able to bird Pueblo REs with Van Truan and Brandon a few years ago,
and was blown away by the diverse (regular-?) species down there. Front
Range effect - Wow!!
Have fun!
Tim Barksdale
Mokane, MO
Choteau, MT
On Friday, January 17, 2025 at 10:31:17 AM UTC-6 Mike Britten wrote:
> 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 <goldene......>
> 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 <rori......>
>> 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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