Northern Saw-whet Owl banding

The smallest owl in the eastern U.S. (about the size of a pop can), the Northern Saw-whet Owl (Aegolius acadicus) is highly migratory. In limited experiments with owl banding prior to 1999, the Rouge River Bird Observatory captured 15 saw-whet owls on campus. During several fall migrations (1999, 2000, 2002), RRBO dedicated some evenings to gauge the extent of saw-whet owl migration through our area.

Protocol

Passive mist netting (setting up lines of nets in areas where owls are thought to travel) is one way of capturing saw-whet owls. However, the use of an audio lure, a continuously looping tape of a saw-whet owl call, increases capture rates spectacularly.  Our set up consisted of two stations about .25 miles apart (0.4 km).  Each station has three 12-meter mist nets of 38 mm mesh arranged in a triangle or a “V”, with the audio lure placed in the center.  Weather permitting, we operated 3 nights a week from mid-October through mid-November from 8 PM to midnight.

Visit the Project Owlnet web site for more information on saw-whet banding, including how determining age and sex, general protocols, and other information.

Results

Below is a list of the owls banded during this project. The following paper was published on the results of the first two years of research:

Craves, J. A., and J. Schultz.  2000. Fall migration of Northern Saw-whet Owls at an inland, urban site: Univ. of Michigan-Dearborn, Wayne. Co. (pdf) Michigan Birds and Natural History 7:87-92.

Age and sex codes used below:
HY = hatching-year (juvenile); SY = second-year (born last calendar year); ASY = after second year (at least 2 years old); M = male; F = female; U = unknown age or sex

1999 banding results

October 24     3 hatching year (HY)
October 26     1 HY
October 29     1 HY plus a HY gray morph Eastern Screech-Owl
November 5     1 recap from October 24, 1 recap screech owl from May 1999
November 6     2 HY, 2 second-year (SY), one a female
November 7     3 HY, one a male,  one a female 1 SY-F
November 9     3 HY, one a male, one recap from Nov 7
November 11     one recap from Nov 9
November 12     4 HY, one a male
November 13     No owls captured; one heard
November 14     No owls captured
____________________
1999 totals:
2 E. Screech-owls (1 a recap)
20 N. Saw-whet Owls (plus 3 recaps) — HY=17, SY=3;  M=4, F=3, U=13
5.43 NSWO per 100 net hours

Fresh, uniform flight feathers indicate this is a hatching-year bird.

2000 banding results

October 8     No owls
October 10     No owls
October 13     1 SY-F, 1 SY-U
October 14     1 HY-F
October 16      No owls
October 17     No owls (rained out)
October 20      No owls
October 21     No owls
October 22     1 SY-F
October 27     No owls (wind)
October 29     Recap of a 10/13 bird
November 3     No owls
November 4     No owls
November 6     No owls
____________________
2000 totals:
4 N. Saw-whet Owls (plus 1 recap) — HY=1, SY=3; M=0, F=3, U=1
1.9 NSWO per 100 net-hours

2002 banding results

October 14     No owls
October 17     Rain
October 19     No owls
October 21     1 Eastern Screech-Owl (gray)
October 24     No owls
October 27     1 Northern Saw-whet Owl – HY-F
October 28     1 Eastern Screech-Owl (gray)
November 2     1 Eastern Screech-Owl (gray)
November 3     No owls
November 4     No owls
November 7     No banding – wind
November 9     Rain
November 13     No owls
November 17     1 Northern Saw-whet Owl – HY-F
November 23     1 Northern Saw-whet Owl – HY-U
November 24     No owls – closed early due to snow
November 25     Recap of Oct 28 Eastern Screech-Owl
November 27     No owls
____________________
2002 totals:
3 Eastern Screech-Owls
3 N. Saw-whet Owls — HY=3, SY=0; M=0, F=2, U=1
0.6 NSWO per 100 net-hours

Saw-whet owls are found nearly every year wintering on campus. This bird was present 28 Dec 2001 - 4 Jan 2002.

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