Re: [cobirds] Ode to Petrochelidon Caution

[David Tønnessen]

Hey Tony,

Thanks for posting an article on Petrochelidon identification! I have yet
to read that piece, so my points on field marks between the two swallows
are not in direct reference to it. My opinion on the ID  is influenced by
countless observations of young and adult Cliff and Cave Swallows in the
field, and discussion with other birders.

I'll join in congratulating Steve Mlodinow on his find, who demonstrates
over and over again what an exceptional birder he is.

My point here still stands; young Cliff vs Cave Swallow is a very
challenging ID with more caveats than most birders realize, so to identify
even a previously reported individual should be exercised with utmost
caution. I suspect Tony's article illuminates this as well.


Best,

David Tonnessen


On Thu, Aug 20, 2020, 2:02 PM coloradodipper via Colorado Birds <
cobirds@googlegroups.com> wrote:

> All:
>
> I wholeheartedly agree with David's main point in his posted... criticism,
> that main point being that identifying Cave Swallow in Colorado requires
> utmost caution. However, his post contains numerous inaccuracies that serve
> only to make the situation more confusing.
>
> It is a rare juvenile Cliff Swallow sporting the "golden/bronze forehead
> and throat patches" typical of adult Cave Swallow (despite my unfortunate
> wording in the Cave Swallow paper; see link further below), which is what
> has been reported recently from John Martin Reservoir. As example, see the
> large selection of photos in the eBird/Macaulay photo archive of juvenile
> Cliff Swallows here:
>
>
> https://ebird.org/media/catalog?taxonCode=cavswa=p=Cave%20Swallow%20-%20Petrochelidon%20fulva=j
>
> Each page of the photo archive is supposed to show 50 photos, though I've
> never tested that contention, though the number is certainly something
> close to 50. Regardless, I went through four pages of photos (ignore the
> occasional mis-aged adult Cliff Swallow photos) without finding a single
> bird that would have caused me pause in the field. I suspect that if one
> keeps clicking on the "Show More" link at the bottom of the page, one may
> get thoroughly tired of the exercise before one finds a photo of a
> correctly identified juvenile Cliff Swallow that sports a forehead and
> throat pattern like that of an adult Cave Swallow.
>
> There are multiple factors behind the dis-similarity of appearance of
> forehead and throat color of juvenile Cliff Swallow to the appearance of
> adult Cave Swallow, even of juvenile Cave Swallows. The primary one of
> these is that most juvenile Cliff Swallows have a variable number of white
> feathers on the head, particularly on the forehead and throat, ranging from
> just a feather or few
> 
>  to
> extensive patches of white
> 
> (not rarely). This tendency is also true of juvenile Cave Swallows (as
> here
> ).
> In fact, this presence of white feathers is so frequent in juveniles in the
> genus Petrochelidon that it is a useful feature in helping to rule out
> either of those species when looking at juvenile Barn Swallows (genus
> Hirundo), an all-too-frequent ID stumbling block (see my paper on Barn
> Swallows in non-adult plumages in the latest issue of Colorado Birds).
>
> For those juvenile Cliff Swallows whose throats are not covered in white
> feathers, many have throats that are more extensively dark than even the
> throats of adult Cliff Swallows:
>
>
> https://macaulaylibrary.org/asset/248282551#_ga=2.21838323.931725895.1597683811-1184313056.1549327880
>
>
> https://macaulaylibrary.org/asset/239953441#_ga=2.257260995.931725895.1597683811-1184313056.1549327880
>
>
> https://macaulaylibrary.org/asset/255579311#_ga=2.194345189.931725895.1597683811-1184313056.1549327880
>
> Given the variability in throat coloration and pattern in juvenile plumage
> of Cliff Swallow, I would not be surprised if there is the odd individual
> or two whose forehead and throat color and pattern approximated the
> appearance of that of adult Cave Swallow. However, such birds are almost
> certainly very rare, possibly rarer than Colorado Cave Swallows.
>
> However, skilled and experienced birders know that single-character
> identifications can lead to error, and in my paper on juvenile plumages
> of Cliff and Cave swallows
> , I
> twice suggest that using multiple aligning characters to make
> identifications of juvenile Cliff and Cave swallows is important.
>
> I interpreted Mr. Tønnessen's wording "depending on age" when apparently
> referring to juvenile Cliff Swallow plumage to mean that their appearance
> was changing in some significant manner, despite that the 

Re: [cobirds] Ode to Petrochelidon Caution

[coloradodipper via Colorado Birds]

All:
I wholeheartedly agree with David's main point in his posted... criticism, that 
main point being that identifying Cave Swallow in Colorado requires utmost 
caution. However, his post contains numerous inaccuracies that serve only to 
make the situation more confusing.
It is a rare juvenile Cliff Swallow sporting the "golden/bronze forehead and 
throat patches" typical of adult Cave Swallow (despite my unfortunate wording 
in the Cave Swallow paper; see link further below), which is what has been 
reported recently from John Martin Reservoir. As example, see the large 
selection of photos in the eBird/Macaulay photo archive of juvenile Cliff 
Swallows here:
https://ebird.org/media/catalog?taxonCode=cavswa=p=Cave%20Swallow%20-%20Petrochelidon%20fulva=j

Each page of the photo archive is supposed to show 50 photos, though I've never 
tested that contention, though the number is certainly something close to 50. 
Regardless, I went through four pages of photos (ignore the occasional mis-aged 
adult Cliff Swallow photos) without finding a single bird that would have 
caused me pause in the field. I suspect that if one keeps clicking on the "Show 
More" link at the bottom of the page, one may get thoroughly tired of the 
exercise before one finds a photo of a correctly identified juvenile Cliff 
Swallow that sports a forehead and throat pattern like that of an adult Cave 
Swallow.
There are multiple factors behind the dis-similarity of appearance of forehead 
and throat color of juvenile Cliff Swallow to the appearance of adult Cave 
Swallow, even of juvenile Cave Swallows. The primary one of these is that most 
juvenile Cliff Swallows have a variable number of white feathers on the head, 
particularly on the forehead and throat, ranging from just a feather or few to 
extensive patches of white (not rarely). This tendency is also true of juvenile 
Cave Swallows (as here). In fact, this presence of white feathers is so 
frequent in juveniles in the genus Petrochelidon that it is a useful feature in 
helping to rule out either of those species when looking at juvenile Barn 
Swallows (genus Hirundo), an all-too-frequent ID stumbling block (see my paper 
on Barn Swallows in non-adult plumages in the latest issue of Colorado Birds).
For those juvenile Cliff Swallows whose throats are not covered in white 
feathers, many have throats that are more extensively dark than even the 
throats of adult Cliff Swallows:
https://macaulaylibrary.org/asset/248282551#_ga=2.21838323.931725895.1597683811-1184313056.1549327880

https://macaulaylibrary.org/asset/239953441#_ga=2.257260995.931725895.1597683811-1184313056.1549327880

https://macaulaylibrary.org/asset/255579311#_ga=2.194345189.931725895.1597683811-1184313056.1549327880

Given the variability in throat coloration and pattern in juvenile plumage of 
Cliff Swallow, I would not be surprised if there is the odd individual or two 
whose forehead and throat color and pattern approximated the appearance of that 
of adult Cave Swallow. However, such birds are almost certainly very rare, 
possibly rarer than Colorado Cave Swallows.
However, skilled and experienced birders know that single-character 
identifications can lead to error, and in my paper on juvenile plumages of 
Cliff and Cave swallows, I twice suggest that using multiple aligning 
characters to make identifications of juvenile Cliff and Cave swallows is 
important.
I interpreted Mr. Tønnessen's wording "depending on age" when apparently 
referring to juvenile Cliff Swallow plumage to mean that their appearance was 
changing in some significant manner, despite that the plumage has been worn for 
only a short time by mid-August and that Cliff Swallows molt on the winter 
grounds. If I read more into that possibly throwaway phrase than was intended, 
then I apologize to David.
David seemed to take an uncited swipe at my above-linked paper on juvenile 
plumages of Cliff and Cave swallows when he suggested that my thesis of Cliff 
Swallows having consistently more and larger dark patches on the lateral 
under-tail coverts than shown by Cave Swallow was not reliable. While I 
discovered that ID character while doing the research for that paper, further 
extensive personal experience with both Cliff and Cave swallows in the field in 
many parts of the US has made me more certain of the efficacy of that field-ID 
character when proper precautions about lighting and viewing angle are taken. 
Are there Cliff Swallows with less-noticeable or even absolutely fewer and 
less-obvious markings on those feathers? I have no doubt there are, given the 
variability inherent in the biological process of recombinant DNA that produces 
organisms like Cliff Swallow and Cutthroat Trout and even that epitome of 
variability known as Homo sapiens. As I stated in the swallow paper and in 
nearly countless other ID articles and photo-quiz solutions, relying on a 
single character is problematic, at best, and decidedly problematic in most