[NatureNS] Boreal Birds moving south this winter

Date: Thu, 22 Nov 2007 07:39:47 -0400
To: naturens@chebucto.ns.ca
From: Blake Maybank <maybank@ns.sympatico.ca>
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Hi NatureNS;

The following message posted elsewhere should be of interest to 
NatureNS birders.  We are certainly seeing shrikes this winter, and 
perhaps we'll be fortunate and snag a Great Gray Owl. . .


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Date:    Wed, 21 Nov 2007
Subject: Boreal Birds - Ontario Updates

Don Sutherland of the Ontario Ministry of Natural Resources (OMNR)
tells me that the abundant meadow vole population last summer in the
Hudson Bay Lowlands has almost certainly crashed. OMNR biologists did
not see meadow voles in October and early November in areas where
they were abundant in August. Newton (2006) states that microtine
crashes often happen quickly following high populations.

Owls: The high small mammal populations last summer in central and
northern Ontario meant that most owls had an excellent breeding
season with abundant prey to feed growing young. Note that most
northern forest owls are rarely if ever affected by cold temperatures
and deep snow unless they are starving. Small mammal populations
(mainly voles) drive their breeding, abundance and movements.

Northern Saw-whet Owl: A red-backed vole (preferred prey in Ontario)
and deer mouse crash likely account for the very large flight this
fall with hundreds recorded at banding stations.

Boreal Owl: I'm not aware of any Boreal Owl sightings this fall in
Ontario, but the heavy flight of Saw-whets and low vole numbers
suggest some may come south. Boreal Owls can take larger prey than
Saw-whets such as Northern Flying Squirrels. Two Boreal Owls have
been banded so far this fall at L'Observatoire d'oiseaux de Tadoussac
northeast of Quebec City on the north shore of the St. Lawrence
River. The observatory is situated along the migratory route of the
Boreal Owl. This cyclic owl often moves only short distances so it is
best monitored by northern observatories.

Great Gray Owl: One was seen on 19 November near Peterborough in
central Ontario and another possible recent sighting in Muskoka. The
crash of meadow voles (preferred prey in Ontario) in northern Ontario
may cause more to show up farther south. However, Great Grays have
the uncanny ability to find areas with high vole densities. They stop
moving when they find abundant voles.

Barred Owl: They are moving, with several reports along north shore
of Lake Ontario, away from their normal habitats. This movement is
likely linked to a crash of red-backed voles, deer mice and other
small mammals in the Great Lakes - St. Lawrence Forest and southern
Boreal Forest.

Northern Shrike: The big southward movement this fall is probably
resulted from the meadow vole crash in the boreal forest. Although
Northern Shrikes eat small birds; they are mainly a vole specialist
in winter. Birds are a buffer and form a greater proportion of
Northern Shrike prey when voles are scarce.

Boreal Chickadee: Indicators of a small movement include Bob
Knudsen's report yesterday from Sault Ste. Marie to Ontbirds, a flock
of 13 seen recently by Erwin Meissner near Massey west of Sudbury,
and a report from Stephen O'Donnell of more sightings than usual near
Sundridge north of Huntsville. A few may get as far south as Lake
Ontario. Boreal Chickadees prefer thick conifers especially spruce.
Listen for their husky calls among flocks of Black-cappeds, which had
a significant southward movement this fall.

Common and Hoary Redpolls - Subspecies: This year's big flight is
providing an opportunity to study two subspecies of the Common
Redpoll and perhaps two subspecies of Hoary Redpoll. Check link below
to Tommy Thompson Park Bird Research Station in Toronto
http://www.ttpbrs.ca/ This site has recent photos of two subspecies
of the Common Redpoll (flammea and rostrata) and photos of a Hoary
Redpoll (subspecies exilipes). They call the rostrata subspecies the
"Greenland" subspecies of the Common Redpoll, but the common name
used in most of the literature for rostrata is "Greater" Common
Redpoll. The name Greenland Redpoll was normally restricted to the
nominate subspecies hornemanni of the Hoary Redpoll. Sibley (2000)
adds to the confusion by using Greenland for the northern subspecies
of both Common and Hoary Redpolls. I suggest not using Greenland
Redpoll because it is now used for the subspecies both species. In
fact, both rostrata Common Redpoll and nominate hornemanni Hoary
Redpoll have extensive breeding ranges in Canada so why even mention
Greenland, which is misleading.

The "Southern" Common Redpoll (flammea) is the commonest redpoll in
southern Canada. It breeds as close as northern Ontario. The
"Greater" Common Redpoll (rostrata) breeds on Baffin Island and
Greenland. The "Greater" Common Redpoll is normally a winter visitor
in small numbers. Rick Poulin (reported by Pittaway 1992)) banded
hundreds of redpolls in the 1980s near Ottawa and found "Greater"
Common Redpolls more common than Hoarys during some winters.

The "Southern" Hoary Redpoll (exilipes) breeds in the low Arctic
south to extreme northern Ontario. It is the usual Hoary seen in
southern Canada in winter. "Hornemann's" Hoary Redpoll is the rarest
redpoll in southern Canada. It breeds in high Arctic Canada and
Greenland. Classic adult males are very large and overall much whiter
with less streaking on the sides, and immaculate undertail coverts.
Adult males have less pink with some having a mere trace of a pink
suffusion on the breast. Not all redpolls will be identifiable to
subspecies or even species, but most individuals can be distinguished
with considerable confidence.

Acknowledgements: I thank the following for keeping me informed: Ken
Abraham (OMNR), Michel Gosselin (Canadian Museum of Nature), Jean
Iron (Toronto), Erwin Meissner (Massey, Sudbury District), Marty
Obbard (OMNR), Stephen O'Donnell (Sundridge, Parry Sound District),
Don Sutherland (OMNR), Ron Tozer (Algonquin Park), Mike Turner
(Haliburton Highlands) and Kirk Zufelt (Sault Ste. Marie, ON).

Literature Cited and Websites:

Newton, Ian. 2006. Advances in the study of irruptive migration.
Ardea 94(3): 433-460. This is the most informative paper on irruptive
species by a winter finch and raptor expert.

Pittaway, R. 1992. Recognizable Forms: Redpolls. Ontario Birds 10(3): 108-114.
Sibley, D.A. 2000. The Sibley Guide to Birds. Alfred A. Knopf, New York.
Tommy Thompson Park Bird Research Station, Toronto, Ontario. Website
http://www.ttpbrs.ca/
Winter Finch Forecast 2007-2008. Archived at
http://www.ofo.ca/reports%20and%20articles/winterfinches.php

Ron Pittaway
Minden & Toronto ON
jeaniron@sympatico.ca


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-----------------------------------------------------------------------------
Blake Maybank
maybank@ns.sympatico.ca

Editor, "Nova Scotia Birds"

author, "Birding Sites of Nova Scotia"
http://maybank.tripod.com/BSNS.htm

144 Bayview Drive
White's Lake, Nova Scotia,
B3T 1Z1, Canada

(902) 852-2077  
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Hi NatureNS;<br><br>
The following message p