1	Migration of Northern Saw-Whet Owls In Penna – 2006 or Waiting for Godot… Presented by Deborah Danila On December 21, 2006
2	2004 Migration (513 owls):
3	2006 Migration (202 owls):
4	How to explain the difference? Saw-Whets are both migratory and nomadic Show little faithfulness to nesting sites and select instead an area with a high vole population (same for wintering site?) NSWO are present year-round on their breeding range Many (not all) move south in Autumn (irruptive migrant) There is a large fluctuation in the number of individuals migrating each year: Our seasonal totals have ranged from 727 in 1999 to 23 in 1997 with a 10 year average of 366 Could be result of the degree of breeding success, but Many adults migrate, so breeding success alone cannot explain the irruptive nature of NSWO migration
5	Other Things to Consider: Migration may also be affected by variation in the degree of competition for seasonally available resources (food, habitat, perch sites) More owls (good breeding success) and/or fewer resources (fluctuation in population of prey species) NSWO are small-bodied, with high mass-specific metabolic costs They migrate using powered, flapping flight, and They don’t tend to build up huge fat reserves like long-distance migrants Must continue to hunt during migration which, as a result, may progress at a more leisurely pace There’s competition for resources at stopovers during migration, too
6	According to one study of the years 1994 to 2000, In Irruptive years (1995, 1999): A larger number of owls migrate Dominated by Hatch Year birds Body mass and body-condition indexes significantly lower for all owls, and particularly for immature owls – evidence of competition for the available resources Low-Recapture Rate: A smaller number of owls elect to stopover Population of prey species along the migration route can diminish quickly, and the owls in good condition move on sooner “…minimizing length of stopover to the extent that energetic condition allows.”
7	And, in Non-Irruptive Years: Dominated by Adult birds Recapture rates 3x higher Significantly higher for Adults in good condition Stopovers twice as long When there is less competition, more experienced adults in good condition seem better able to establish residency along the migration route, and Immature owls and those in poor condition must move on when they can.
8	So What happened this year? (A very anecdotal view) Early reports from the north suggested the owls were late, but coming in above-average numbers. Banding site along the St. Lawrence in Quebec captured 27 saw-whets in their first two weeks (after netting only 28 total all of last season) and reported their highest total count since 1999 (128). Ottawa set new record: 30 in one night WhiteFish Point Bird Observatory in Paradise, Michigan, reported a ‘Spectacular Season!’ with all-time high of 325 Saw-whets Minnesota bander, captured over 500 owls working on his own, including one night of almost 80. In parts of the upper Great Lakes, there is a tremendous amount of habitat to the north, and the funneling effect of the lakes, can channel the birds through certain areas. Linwood Springs,Wisconsin, reported an all-time high of 77 saw-whets on one night, breaking a decade-old record of 71 birds.
9	On the other hand… Things were ‘miserably slow in western Maryland’ SkyTop in NE Penna claimed ‘worst season ever’ There was A LOT of reading, and napping, and card-playing and general twiddling of fingers at Hidden Valley, PA On 11/3 West Chester NY had only 3 owls, compared to 26 last year at that same time Greene County Indiana had the “Slowest season so far” (18) WoodRiver NE, with a total of 11, reported ‘very poor capture rate’ Western VA reported only 61 for the season, less than half of total in past two years This year’s migration appears simply to have stopped for most of the saw-whets somewhere north of our banding sites Migration is essentially about finding food, and Perhaps mild weather, and high prey populations in the north kept the owls out of reach this year (several banders reported more birds with above-average weights)
10	What can we look forward to? According to the annual predictions of Ron Pittaway (of the Ontario Field Naturalists): “The widespread abundance of seeds, berries, nuts and fruits (mast) is providing a huge food supply for small mammals such as voles, so their numbers should be increasing. Most boreal forest owls (Northern Hawk Owl, Great Gray Owl, Boreal Owl) likely will stay close to breeding territories this winter. Increasing numbers of small mammals will increase owl breeding success next spring and summer.” BUT will they come south?? In the eternally optimistic view of Scott Weidensaul: “…his observation regarding vole populations bodes very, very well for next year, especially considering the large number of young saw-whets being reported at northern banding stations this season. A well-provisioned female saw-whet may lay up to 11 eggs, which means 2007 may be the kind of major invasion year we haven't seen since 1995 and '99. We'll keep our fingers crossed...”
11	"Whoo Am I?" Whoo Am I? Shadow in the trees. Wisp in the night. Clearly he sees, without any light. Chameleon by day. Killer by night. Stalking his prey, in the pale moonlight. By: Daryl Aspery “Migratory birds do, in the end, integrate and reflect environmental change on the broadest of scales. The sobering truth is that whether future generations can enjoy this truly remarkable phenomenon of nature will be more a measure of whether humanity will have achieved sustainable development than anything else.” - Dr. Thomas E. Lovejoy
12	References: Annual migration density and stopover patterns of Northern Saw-whet Owls (Aegolius acadicus) Auk,The, Oct 2002 by Whalen, David M, Watts, Bryan D Daily Email Updates from Scott Weidensaul Reports on SawWhetNet listserve Atlas of Bird Migration – Tracing the Great Journeys of the Worlds’ Birds – General Editor Jonathan Elphick Living On The Wind, Scott Weidensaul