Thursday, December 12, 2013

About the Snowy Owl Invasion

Some interesting information about the snowy owl invasion along the east
coast. From Nature NB. One at Bocabec River this past weekend.


Snowy owl.
Snowy owl. (Photo credit: Wikipedia)

Date: Mon, 9 Dec 2013 15:19:36 -0400
Subject: Snowy Owl still in Jemseg

Monday afternoon, December 9,

Just saw the SNOWY OWL (Harfand des neiges) coming back from Fredericton
on the new highway perched in a tree just before the Jemseg's bridge.
It was in the same area that Jim Goltz reported this morning. My first
one, finally.

Brigitte Noel

Date: Mon, 9 Dec 2013 17:36:15 -0400
Subject: Snowy Owl at Jemseg update

This afternoon (Dec. 9, 2013) Peter Pearce, Ronnie Phillips and I went
to Jemseg in search of a SNOWY OWL reported earlier today. We proceeded
along Route 105 (old TCH) all the way to Jemseg without success. We then got on Route 2 (new TCH) and headed back toward Fredericton
whereupon we found a Snowy Owl perched atop a tree very near where Jim Goltz reported seeing one this morning. When we reached Route 105 we drove back toward Jemseg and Ronnie spotted a Snowy Owl high in a tree on the bank of the St. John River. We were able to get great looks at it and we felt it looked slightly different from the other one sighted. Since we were only about 700-800 metres away we assumed it must be the same owl. Once again we got on Route 2 and headed toward Fredericton.
Although distant, we could see the owl along the river. We went a bit farther when Ronnie discovered Snowy Owl high in a tree out in the marsh toward Grand Lake. Thus there are two Snowy Owls at Jemseg or one very fast one.

Don Gibson


Date: Mon, 9 Dec 2013 22:03:59 -0400

I'm taking the liberty of re-posting a submission from Maine Birding
which addresses two key points about the current owl irruption: aging &
sexing individuals by plumage and the cause of the irruption.

Hello Maine Birders:

A friend and former colleague of mine at Hawk Mountain, Jean-Francois
Therrien, conducted his Ph.D. research on Snowy Owls in NE Canada
recently. 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!"

When JF wrote: "see attachment" he was referring to a PDF 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 with older birds but it 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.

Good birding,

Eric Hynes

Hinesburg, VT


Date: Mon, 9 Dec 2013 21:09:28 -0500
Subject: Maine Snowy Owl map...update

Updated map of Maine Snowy Owls as of 9 Dec 2013

Date: Mon, 9 Dec 2013 23:49:22 -0400

Hello Ralph and all.

Interesting stuff. But my question would be : Why all of these Snowies
in N.-B.? In good years we get a couple here and there and I remember
something like six or seven on the Tantramar maybe 10 years ago but
nothing like this. I am counting something like 40 + already. Now last
year at this time if you would have asked I would have said that owls
are reluctant in general to cross big bodies of water so that would
explain why we don't get as many here as more to the West (were the
Saint -Lawrence become more narrow) but while talking with Joël Betty
last spring (works with J-F Therrien on the nesting grounds) he
explained that recent research seems to show that Snowies are quite
adapted to water and that some might even live on the ice flows during
winter where they hunt sea ducks that hold out in the opening in the ice
sheet. So crossing the Gulf is probably not a problem. But still why so
many on the coast compared to other years? Maybe there are just so many
(there is some talk of record year in Québec) that they are overflowing
even here. Or maybe something else but what? Any other ideas out there?.
In any case enjoy, cause it might not come around again for a very long

Good birding.

Roger Leblanc

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