McGILL BIRD OBSERVATORY

OWL MIGRATION MONITORING PROGRAM 2011

McGill Bird Observatory began experimenting with Northern Saw-whet Owl monitoring in the fall of 2004, which resulted in 17 saw-whets banded, plus an Eastern Screech-Owl as an unexpected bonus.  Similar totals were banded in 2005 (17) and 2007 (15), with 2006 and 2008 skipped due to a shortage of experienced owl banders.  In 2009, the program was relaunched at a different location within MBO and effort was expanded, resulting in a dramatic improvement in results - 76 saw-whets and 2 screech-owls banded.  Based on this success, MBO applied for funding to support full coverage of the 2010 fall migration period, and thanks to a research grant from Bird Protection Quebec, operations were expanded from September 25 to November 13, during which 125 saw-whets and 2 screech-owls were banded.  Based on that success, we followed a similar approach in 2011 and ended up with an even higher count of saw-whets - see the details below.


One of over 200 Northern Saw-whet Owls processed at MBO this fall; unlike most that we banded during nocturnal operations, this was one of a few that got caught in the early morning as part of our Fall Migration Monitoring Program
.
(Photo by Simon Duval)

Banders-in-charge:  Bob Barnhurst, Simon Duval

  

2004
2005
2007
2009
2010
2011
TOTAL

# birds (and species) banded

18 (2)
17 (1)
15 (1)
78 (2)
124 (2)
199 (1)
451 (2)

# birds (and species) repeat

--
--
--
5 (1)
5 (1)
2 (1)
12 (1)

# birds (and species) foreign

1 (1)
--
--
2 (1)
2 (1)
9 (1)
14 (1)

# species observed

not
counted
not
counted
not
counted
5+2
4+8
not
counted
5+8

# nights banding

11
8
11
28
35
38
131

# net hours

208.8
224.7
293.6
698.0
1323.6
2588.3
5337.0

# birds banded / 100 net hours

8.6
7.6
5.1
11.2
9.4
7.7
8.5

Note: table includes only nocturnal banding (owls); species observed represent owls+others

Like in 2010, our approach this fall was to have nightly coverage (weather permitting) over a core six-week period from September 26 to November 6, supplemented with a few additional nights under good conditions until mid-November.  We again operated seven nets - five of them dedicated 60-mm mesh owl nets and two of them 30 mm passerine nets that served double duty with our fall migration monitoring program.  As usual, we broadcast an audiolure to draw the owls in, following the standard protocol shared by most saw-whet researchers.  The key difference compared to last year is that the banders, especially Bob, were determined to make the most of a short season and often continued much longer into the night.  As a result, we set several records this fall, although our capture rate was actually below average compared to previous years.

As usual, few owls were moving yet at the end of September. On our first night, the only owl we caught was one banded at MBO last October, perhaps a local resident; over the rest of the first week only two new owls were banded (although three nights of rain had an influence on the results too).  Things took a sharp turn for the better the following week, with 45 new owls (and our first two foreign recaptures of the season) over the nights of October 4 and 5, and a record high total of 75 new owls for the week.  Our third week also began well, with 14 more new owls and two more foreign birds, but then we had three shutouts in a row, followed by two nights lost to wind and a lone owl on the final night. Migration picked up again in the fourth week, with a single-night record of 30 new owls (and two more foreign recoveries) on the night of October 22, and another 34 new owls and two foreign birds over the other six nights.  Migration tapered off after that, with 30 more new owls and our ninth (and final) foreign recapture in week 5, and 9 more new owls in week 6, consistent with the decline we've typically seen as the calendar turns to November.  Between November 7 and 15, a few more nights of effort brought us to 199 new saw-whets for the season, and a total of 451 over our six seasons of owl monitoring to date.

As of the end of the season, we know the origins of 8 of the 9 foreign-banded birds we recaptured this fall.  Six of them were banded last fall, while the other two were from 2009.  Three of the owls were banded at Prince Edward Point Bird Observatory on the north shore of Lake Ontario, and one of the others was also an Ontario bird, but from Thunder Cape Bird Observatory on the north shore of Lake Superior, roughly 1200 km from MBO.  The other owls were from the northeast US, two of them from Pennsylvania, and one each from Massachusetts and Virginia.  Interestingly, we had a previous recapture of a saw-whet from the same Virginia banding station back in 2009.   We look forward to learning where the ninth owl was banded.

Compared to last year, we had somewhat better weather overall, losing only 7 nights during the main season, compared to 12 in 2010.  However, these nights were clustered in two periods (three of four nights between September 29 and October 2, and four of six nights between October 14 and 19), and the second in particular has traditionally been a busy period at MBO, so we wonder what effect that might have had on numbers.  It is also worth noting that on some additional nights the weather was initially poor and would have resulted in cancellation last year, but this year we sometimes waited and started later.  As always, we collected data on effort and weather conditions, which will allow us to compare results across years despite variability in coverage.

This year just under half (48%) of the saw-whets banded were hatch-year birds, compared to 70% last year and 76% in 2009; the decline in the proportion of hatch-year individuals (an indicator of productivity) appears to be loosely correlated with our hourly capture rate.  The proportion of second-year birds was higher than usual this year (40%), compared to 20% last year and 9% in 2009.  The frequency of older birds has remained more constant (12% this year, compared to 10% last year and 15% in 2009).  Females dominated the captures as usual, with 81% this year, versus 7% males and 12% unknown, based on intermediate size and weight.

As always, the success of our program was due to the human element - our dedicated banders, and a full complement of volunteers on most nights throughout the season.  We look forward to resuming our owl work in September 2012; to help us with the costs of the program, please consider adopting one of this year's owls.  You will receive a personalized 8.5" x 11" certificate, including a photo of your owl and details such as its age, sex, weight, and date banded - and we will notify you if the owl is subsequently reported elsewhere.  Click here for details on how to request an adoption.  

 

2002- The Migration Research Foundation Inc.