Date: 7/4/25 10:30 am From: Zac Denning via groups.io <zdenning1...> Subject: Re: [northbaybirds] Odd loon at Bodega Bay
PS - I should have mentioned that the white flank feature helps distinguish
between Pacific and Arctic Loons, but otherwise isn’t especially unique or
useful for ID in other loon species.
Zac Denning
On Fri, Jul 4, 2025 at 9:56 AM Zac Denning via groups.io <zdenning1=
<gmail.com...> wrote:
> Hi Gene,
>
> Loons can be flustering.
>
> White flanks aren't that unusual for a first year Common Loon, and their
> appearance also really varies. There's also variation amongst individual
> loons in their plumage (plus wear / fading), as well as the bird's posture.
> In addition, loons can control their buoyancy by inflating their air sacs,
> or (with the help of their solid bones), when they deflate their air sacs,
> they can ride low in preparation for diving. This means that the amount of
> visible white flank will also vary depending on the bird's buoyancy at that
> moment.
>
> Here are photos of a single individual first year Common Loon, showing
> how buoyancy affects its appearance:
> Low-riding - no flank showing: https://macaulaylibrary.org/asset/621303059 > Higher-floating bird, with lots of pale flank:
> https://macaulaylibrary.org/asset/620522204 > <https://macaulaylibrary.org/asset/101530261> >
> The head position, with bill tilted slightly upward, isn't diagnostic by
> itself. Many loons will tilt their bills up slightly, and it doesn't look
> very pronounced in your photos. This feature is most useful in Red-throated
> loons, which spend more time with their bills tilted upwards. But as
> always, using a combination of features (posture, plumage, etc) is usually
> most reliable.
>
> In this bird, the jagged border of the neck line, and deeply angled lower
> mandible, points away from a Pacific/Arctic Loon.
>
> I hope that helps,
>
> Zac Denning
>
> On Fri, Jul 4, 2025 at 8:15 AM NANCY AND EUGENE HUNN via groups.io
> <enhunn323...> wrote:
>
>> Leaning towards.immature female COLO rather than Arctic but still puzzled
>> by white flanks and bill tilt.
>>
>> Gene Hunn
>> Petaluma
>>
>>
>
>
