Thursday, January 22, 2015

NSWO Banding

Happy New Year!

I haven't been out birding too much since the start of the new year, so I figured I would catch up on a few posts that have been laying stagnant for a while due to my hectic fall term!  I am surprised that I did not once post about our Owl Banding at Trent U, so I figured it's better late then never!  I published a recent article in the Peterborough Field Naturalists newsletter "The Orchid" on our owl banding, so if anyone is reading from there, a lot of this info will sound familiar!

Since 1999, Dr. Erica Nol has been conducting an annual banding project at Trent University’s James McLean Oliver Ecological Centre near Nogie’s Creek (or Bobcaygeon).  Each day of the week throughout October a bander-in-charge and a group of visitors go to the property to see what they might catch throughout the night. The project has been run soley based on volunteers and donations made by visitors.

Northern Saw-whet Owls (Aegolius acadicus) are the species of owls that we primarily focus on catching and banding.  They are a nocturnal birds that migrate through the Peterborough area every fall, with numbers peaking throughout October.  Northern Saw-whet Owls (NSWO) are robin sized and have large, bright yellow eyes.  They are one of my personal favourites because each individual seems to have their own personality and just burst with attitude.  NSWOs primarily feed on small rodents, however they have trouble hunting in deep snow that leads them to migrate from the boreal forest to areas of lower snowfall.   

Northern Saw-whet Owls are attracted to their territorial calls during the fall and we take  advantage of this for banding.  Three 12m X 2.6m mist nets are set up in a triangular pattern in a wooded area of the property.  An audio lure broadcasts the territorial call, filling the woods with “too-too-too-too” from 8pm until midnight with net checks every 30 minutes.  Each captured bird is removed from the nets and placed into a cloth bag before being brought into the banding station for processing.

Each owl is banded (with a unique 9-digit code), weighed, and the wing chord is measured.  We examine the moulting pattern within the flight feathers of the owl’s wings to determine an age. Alternatively, we can determine age with a small black light. The black light will pick up on traces of pigment left in the feathers showing a pinkish colour (it feels very much like CSI!).  Young birds will have all new feathers, meaning that under black-light all the feathers will have a pink tone to them.  As a bird ages and feathers become older, they will be white under the light.  After second year birds will be a mismatch of pink and white as wing feathers will be a both old and new, being replaced as need be.

This fall, owls were caught and banded on 27 days with a total of 147 NSWOs passing through the station.  Seven of these owls were recaptured birds from previous nights, years or from other stations. 

Hatch year owls (HY, born this season) made up 76% of the owls that were captured this year. Second year owls (SY, born last year) accounted for 8% of the age distribution. After second year owls (ASY, born 2 years ago or more) made up 22%.  1% of owls were not aged or sexed.


Table 1: Age and Sex of NSWO banded at the Oliver Center during fall 2014
HY (f, m, u)
SY (f, m, u)
ASY (f, m, u)
Unknown
Total (f, m, u)
112 (77, 16, 19)
12 (9, 1, 2)
22 (18, 1, 3)
1 (1 f)
147 (105, 18, 24)

The majority of birds were female (71%), followed by unknown sex (16%), and then very few males (13%).  This may sound like a very large number of females, but it seems to be a trend following previous years’ data.  Studies have noted that females tend to migrate further than males. The same can also be said for hatch year owls compared to older owls.

Of the 7 birds that were recaptured, 3 were from other locations.  One owl was banded as an ASY in 2012 at the Prince Edward Point Bird Observatory (PEPBO) near Picton, Ontario and the second was banded at PEPBO as a SY in 2012.  The third recaptured owl was banded in 2012 as a HY in Port Rowan, Ontario. I always love getting birds that have been banded elsewhere because we get to see where they travel to and from, as well as how old they are.  It is also always exciting to have someone else catch a bird you have banded and receiving an email about it being found.

This fall, we shared this fun and unique opportunity with 119 different visitors in the Peterborough and surrounding area!  If you are going to be in the area and interested in joining us next fall (or I guess this fall now!) at the Oliver Centre, feel free to shoot me over an email and your name can be added to the mailing list (tiannaburke@trentu.ca).


Hope everyone is having a great winter so far!

Happy Naturing!