LISTSERV mailing list manager LISTSERV 16.5

Help for VTBIRD Archives


VTBIRD Archives

VTBIRD Archives


VTBIRD@LIST.UVM.EDU


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Monospaced Font

LISTSERV Archives

LISTSERV Archives

VTBIRD Home

VTBIRD Home

VTBIRD  December 2013

VTBIRD December 2013

Subject:

Re: More info on Snowy Owls

From:

Jane Stein <[log in to unmask]>

Reply-To:

Vermont Birds <[log in to unmask]>

Date:

Mon, 9 Dec 2013 12:55:13 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (110 lines)

Thanks for this, Eric. Fascinating stuff.

The info on adjustment of clutch size is particularly interesting. One
thing I've long wondered about is whether the instinct to chase the
young off the winter feeding territory also varies. If there's a
super-abundance of lemmings, one would think they could support a larger
number of owls than usual over the winter.

If you happen to talk to Therrien again any time soon, could you ask him
what is known, if anything, about the constancy of winter dispersal
and/or the numbers of young wintering over and how/if those things vary
with the lemming numbers?

Jane
(Shoreham)






On 12/9/2013 12:38 PM, Eric Hynes wrote:
> Hello Vermont Birders:
>
> All this Snowy Owl activity is terribly exciting. If you haven't had a
> chance to get out looking for one yet or if you haven't lucked into seeing
> one despite your efforts, don't worry, more are on the way.
>
> Bruce MacTavish reported to the Newfoundland listserv yesterday a
> conservative count of *over 200* in a single party outing along the eastern
> shore! Based on previous efforts and weather, he felt confident these were
> newly arriving birds. Obviously, we aren't on the East Coast and so are not
> as likely to get "those" Snowy Owls or concentrations of that magnitude,
> but clearly there are more Snowy Owls on the move.
>
> A friend and former colleague of mine at Hawk Mountain, Jean-Francois
> Therrien, conducted his Ph.D. research on Snowy Owls in NE Canada. He
> continues to spend time in northern Quebec in the summer doing research.
> There are several aspects to Snowy Owl behavior and plumage which seem to
> get debated frequently so I reached out to JF for some clarity. I thought
> some members of this birding community might be interested in his reply.
>
> In regards to plumage, most sources are in agreement that males tend to be
> whiter/lighter than females and immature birds tend to be darker than
> adults but these are just gross trends. There is a high degree of variation
> among individuals and some birds have been documented as getting darker
> with age. The darkest males can be darker than the lightest females.
> Thankfully, many birders are reporting to east coast listservs their
> sightings of Snowy Owls. Often the details include "immature male" or
> "adult female." Personally, I am cautious to label most Snowy Owls but I
> thought maybe I was missing something so I asked JF. Here is his reply:
>
> "Concerning age/sex classes: there is no specific criterion to tell them
> apart objectively (as of yet). Some folks have developed a way to tell sex
> among chicks at nest (see attachment), but in the field, especially in
> winter at low latitude, it is pretty much a guess in all cases. The only
> group that we can identify with confidence is adult males. For the rest,
> (except when you are facing a nest and you can tell female from male
> easily), it relies on feelings! People have long thought that snowies were
> getting whiter with age. This was mostly based on captive birds. We got
> lucky and photograph the same female wearing a satellite transmitter in 2
> winters (2008 and 2010). That female actually got significantly darker! We
> were amazed. A specialist of plumage coloration and molt in birds said he
> was unable to understand the actual pattern in snowies (since the number of
> wild bird being captured remains low). So, a lot more debates to come!"
>
> "(see attachment)" refers to a PDF JF sent me of a paper published in the
> Journal of Raptor Research in 2011. (I can forward the PDF if you contact
> me directly - not via the listserv). Researchers accurately predicted the
> sex of 140 nestlings 100% of the time by studying the remiges and retrices.
> Secondaries were best but outer primaries and central/deck tail feathers
> worked as well. The dark "spotting" on the flight feathers of the nestlings
> were comprised of pigmentation running the width of the feathers creating
> bars and circles of pigmentation on either side of the rachis not reaching
> the edges creating spots. Males had more spots than bars and females had
> more bars than spots. So if you feel compelled to label the birds you find,
> be sure to study/photograph the open wing and spread tail carefully. *Note
> - The paper does not talk about the effectiveness of using this protocol on
> anything older than a juvenile so you have to accurately age the bird
> first. It might work but has yet to be studied.
>
> The other area of discussion is the cause of the irruptions. Nobody debates
> the predator-prey connection. Lemmings make up the bulk of the diet on the
> breeding grounds and their populations are cyclical. The size of a Snowy
> Owl clutch is variable. Females assess how successful their mate is at
> bringing her lemmings at the beginning of the breeding season and she lays
> eggs accordingly. In years with lots of lemmings, she will lay lots of
> eggs. Debate comes in when the birds irrupt southward. So, has the lemming
> population crashed and starving birds are forced to migrate or do we see
> them down here when the Snowy Owls have big breeding seasons and there are
> lots of young birds dispersing? I posed this question to JF as well:
>
> "As for the irruption, you are quite right. Almost every year that we see a
> good reproduction in the eastern Arctic, we have some sort of winter
> irruption down in QC and New England. Last summer was fantastic in Northern
> Quebec. I was there at the tip of the province and we found several nests,
> all of which having large clutches and several lemmings piled up on the
> surrounding. We expected to see some irruption because all of those chicks
> are starting to wander around, and they are now reaching our latitudes."
>
> Die-offs eventually follow these spikes as nature corrects itself but I for
> one will be riding the high this winter.
>
> Enough out of me.
>
> Good birding,
>
> Eric Hynes
>

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

July 2021
June 2021
May 2021
April 2021
March 2021
February 2021
January 2021
December 2020
November 2020
October 2020
September 2020
August 2020
July 2020
June 2020
May 2020
April 2020
March 2020
February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003
December 2002
November 2002
October 2002
September 2002
August 2002
July 2002
June 2002
May 2002
April 2002
March 2002
February 2002

ATOM RSS1 RSS2



LIST.UVM.EDU

CataList Email List Search Powered by the LISTSERV Email List Manager