Subject: [Tweeters] Northwestern Crows
Date: Jun 24 12:48:59 2012
From: Eugene Hunn - enhunn323 at comcast.net


Kevin,

Thanks for your detailed summary. It seems to me there is no dispute about
the facts, just how we should interpret them, vis-?-vis species versus
subspecies. I freely admit I have an intellectual attachment to that
old-time biological species concept, the notion that a species is a
population with a distinctive "way of life," that is, oa population that
varies in multiple phenotypic particulars which collectively reflect a
distinctive behavioral and ecological identity. If a species is simply a
clade of a certain time depth, regardless of whether that clade intergrades
over a narrow or wide zone with nearly related clades, we are left defining
a species quite arbitrarily in terms of years of separation. It seems clear
that all living things form one clade at a sufficiently deep time horizon,
which doesn't advance our understanding of evolutionary process at all. So,
I remain unconvinced that the "Alaska Crow" [but recall there are bona fide
American Crows in the Alaskan interior] deserves specific status.

Gene Hunn
Petaluma

-----Original Message-----
From: tweeters-bounces at mailman1.u.washington.edu
[mailto:tweeters-bounces at mailman1.u.washington.edu] On Behalf Of Kevin
Purcell
Sent: Friday, June 22, 2012 3:09 PM
To: Tweeters
Cc: Kevin Purcell
Subject: Re: [Tweeters] Northwestern Crows

Apologies as this is VERY LONG but I think a significant step forward in
talking about the status of the Northwestern Crow. A second short email that
follows this is a short summary with advice for birders (who don't want to
read this stuff).

In a previous message I mentioned the talk I saw James and Renee Ha (at REI
Flagship store on Thursday, February 17, 2011). James presented pretty good
mitochodrial DNA evidence for the Northwestern Crow being a distinct
species.

I recorded this talk for my own use. Those interested can download a copy
from my DropBox. It's a 39MB (quite large) 80 minute AAC audio file that
will play on iPod/iPhone/iTunes and other audio players. The portion of
interest for the distribution of the Northwestern Crow is from 31 minutes to
50 minutes though the whole talk is worth listening to. Click on this link
to get a copy (it's just a URL shortener link to the file).

http://bit.ly/KP9TYt

I've since exchanged emails with James Ha and he told me the paper (Ha,
R.R., Walsh, H., Diniz, F.M., Bentzen, P. The biogeography of north
american crows based on control region mtDNA) is expected to be submitted
for publication this summer.

I summarize James and Renee Ha's argument below. My comments are in square
brackets [ ... ].

Dr James Ha and his father (an animal behaviorist with experience recording
sound on sabatical) one summer recorded crow vocalizations at multiple
locations around the Salish Sea (i.e. in the Georgia Basin/Puget Trough) to
answer the question "is there a statistically significant difference in
Pacific-northwest Crows vocalizations in different locations"

The locations selected are:

Northern/Coastal population (Nanaimo)
Olympic Peninsula population (Sequim State Park) Whidbey Island population
(Lake O'Neil Campgrounds? Cape Disappointment State Park) Southern/Inland
population (the Seattle UW campus)

Evening assembly calls were recorded at 5m to 15m [that 3 times range means
a potential 5.2dB difference in level depending on range differences or 3x
in amplitude]

They looked at:

Peak frequency
Amplitude at certain frequencies (5kHz, 6kHz and 7kHz) - 6kHz for the
reported results Call length in milliseconds

The question: Is there a difference in any of these measures between these
populations of crows.

At 95% confidence limits (p=0.05) there is. Look for clusters in the
variables on two (or more) dimensions e.g. amplitude at 6kHz versus call
length is presented where the difference is largest.

The Nanaimo and Seattle UW campus are clearly distinguished. The Nanaimo
crows have less amplitude at 6kHz and shorter calls than the Seattle crows.
This is what birders hear (lower, hoarser, shorter vocalizations as one
travels north in the Salish Sea).

The birds at intermediate locations have intermediate amplitude at 6kHz and
call length compared to the crows in the north and south.

There is a cline in call parameters. There is no sharp boundary between
these "two groups" of crows.

So what about the birds in SE Alaska (outside of the Salish Sea region). Is
there a difference in calls between them and the Nanaimo crows? They didn't
have the money to go up there and do the same measurements there. [That's a
shame]. The would have liked to do recordings in Juneau and up the Alaskan
panhandle to see if there are changes there.

So there is a north-south cline in the vocalizations in the Salish Sea [at
least at this resolution of measurement]

How is this cline explained? There could be American Crows in Seattle and
Northwestern Crows in Nanaimo and hybrid/intergrade Northwestern x American
Crows in between. Or there could be American Crows in Seattle and
Northwestern Crows in Nanaimo and a discrete mixture of Northwestern Crows
and America Crows at locations in between. Using thier current data they
couldn't distinguish these [Actually I think you might be able to sort this
out by looking at the shape of the clusters but it might be that the
difference is too small to distinguish between them. This is like curve
fitting two peaks. But with better data this might become clear (if you can
reduce the "noise" in the data). How big is the variance in one group
compared to the two end points.]

Conclusion of the vocalization study: there is a significant difference
between the vocalizations of in the north of the Georgia Basin and the south
of the Puget Trough and there is a cline from hybridization or overlap of
call in between those locations.

Hence the need for phylogenetic work.

The Burke Museum funded a postdoc to work with Renee Ha initially to answer
the question "does the genetics of the crows in the Puget Sound [and Georgia
Basin?] differ from those in Alaska". This study expanded (over 10 years or
so) into looking at the phylogenetics of crows across the whole of the USA
and Canada: including the American, Northwestern and Fish Crow (but
excluding the Tamulipas Crow). Using automated sequencing mitochondrial DNA
of 121 tissue samples from museum samples across the US [this is what the
dead birds you hand in].

They found a phylogenetic tree that grouped all American Crows (those from
the east and the west) share a single mtDNA sequence with some single
basepair changes together (in a clade). Another grouping (clade) is of
"Alaskan Crows" (i.e. from samples from crows in Alaska). Samples from crows
on the Olympic Peninsula [and elsewhere around the Salish Sea] are
intermediate between these two groups. The Fish Crows appear as another
clade. As these Fish Crow is an undisputed species it was included as a "out
group" to see if it appeared in the phylogenetic analysis of these mtDNA
sequences as a clade to show that these are actually useful differences.

In their initial work (reported by Renne Ha at the WOS meeting a few years
back) there was a problem: the Fish Crows didn't come out as a distinct
clade (species) which was a problem. This was from an insufficient number of
samples from Fish Crow. When the number of Fish Crow samples was increased
and the phylogentic tree was generated (in 2011) the Fish Crow appears
species.

They also include a cline in the tarsus length of crows sampled along in the
Georgia Basin/Puget Sound: tarsus length increases as the move to the south.

James and Renee Ha conclude that the Northwestern and American Crow seem to
be separate species in their endpoints [i.e. in Alaska and outside the
Pacific Northwest] with as good standing as the Fish Crow.

The Northwestern clade split off from the American clade sometime in the
Pleistocene era [I asked Renee later for an approximate date and, if I
remember correctly she said 100,000 before present].

The crows around the Salish Sea are intermediate between the two clades.
This could be because they American Crows are invading an initial
Northwestern crow population in the Puget Trough and generating a hybrid
zone. Or possibly the two species could be separating out in this region
(given the north to south cline) [e.g. sympatrically if they breed
assortively perhaps based on call or behavior? or parapatrically or
peripatrically by separation into different habitats or niches?]. They
currently can't answer this question.

There are plenty of problems:

The paper isn't published so it hasn't been peer reviewed yet. Perhaps the
referees will find issues with the mtDNA work and the phylogenetics. I
suspect not.

There is no nuclear DNA (nDNA) phylogenetics work. Perhaps this has been
done in the last year or perhaps they've decided to publish without nDNA
work. This did worry Renee Ha last time I talked to her.

They didn't do any vocalization work in Alaska or south of Seattle or more
inland of Seattle. Perhaps there is a small cline continuing say along I90
to the east (after all Eastern birders often comment on how the local birds
sound different) and I5 to the south. This is the sort of work an amateur
bird sound recordist could do (in fact the data probably already exists in
libraries if one could get it in raw form).

This answers some of Eugene Hunns questions:

On Jun 19, 2012, at 2:33 PM, Eugene Hunn wrote:

> In the case of the ?Northwestern Crow,? while crows from the Kenai
Peninsula to the outer Olympic Peninsula may vary little, there is no clear
boundary between those crows and the mass of crows throughout western
Washington.

There is a cline down the Salish Sea basin but the lack of a boundary
doesn't mean the end points don't exist.

> The ecological preference for beach foraging could simply be due to where
the available crow foods are to be found along the densely forested outer
coasts. If there are really two crow species in western Washington there
should (or perhaps ?must?) be a zone of contact, of sympatry, where one
could demonstrate the coexistence of two distinct species populations.

The "zone of contact" is all through the Georgia Basin/Puget Trough. Of
course this also means (as Eugene and others have said) is that there are no
"pure" Northwestern Crows in Western Washington or perhaps even BC.

Perhaps the Northwestern Crow should really be called the "Alaskan Crow"?

> A few mitochondrial DNA differences proves nothing about how the crows
throughout western Washington interact, with each other and with the
environment.

That's true but phylogenetics using mtDNA and nDNA and the phylogenetics are
how species are defined today. You may regret that but it is how most
biologists work today.

This is not a new issue but one that appeared when cladistics started to be
used to generate trees of fossils algorithmically from descriptions features
rather than having a taxonomist make his educated best guess. The book "In
Search of Deep Time" outlines the history of cladistics and documents this
fight (and it was a fight starting in the 1970s) rather well with results
like "there are no fish" (i.e. "the fish" do not form a clade).

Phylogenetics just uses similar techniques to get to the underlying order
carried in the DNA and seems to ruffle the same feathers.

> Has anyone done a comprehensive study of vocal patterns (of breeding
birds) throughout the region. If so, can they demonstrate that there are two
sympatric vocal systems in play? Or, would such a study show a clinal
pattern of variation linking the extreme outer coastal call types with the
calls further south along the coast and/or inland, as with the ?Western
Flycatchers??

Again just because there is a cline doesn't mean there aren't distinct
species at the endpoints (ring species are the extreme example of this and
of course drive "tickers" up the wall).

The counter example is our other favorite hybrid around Western Washington:
the Glaucous-winged x Western Gull. Huge hybridization zone with perhaps 40%
of the birds in the southern Puget Trough being intergrades (the number
varies depending on where you are sampling). They breed assortivley it
seems. Does that make the Glaucous-winged Gull and Western Gull not true
species but just one large Larid species with two different subspecies?

Thanks for reading this all the way through :-)
--
Kevin Purcell (Capitol Hill, Seattle, WA)
kevinpurcell at pobox.com
http://kevinpurcell.posterous.com
http://twitter.com/kevinpurcell

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