[Ontbirds]Boreal Birds - Ontario Updates

[Jean Iron]

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 at sympatico.ca