Design of Backpack for Nanotags on Saw-whet Owls

Tagging
1

I am looking for any advice or experience putting nanotags on small owls. Some projects have put the tags with a leg harness with elastic but the tag failure rate seems high; i.e. the owls may have cut the tags off. The nanotags that I plan to use should have a potential life of two years.

I have put satellite transmitters on larger raptors using Teflon webbing in a backpack configuration with great success.

Has anyone used Teflon webbing or Spectra on small owls? What size was used? How did you attach the nanotag to the webbing?

Any advice will be greatly appreciated.

The members of the Beaverhill Bird Observatory in central Alberta, Canada have donated funds for 50 nanotags to be deployed this autumn.

Cheers
Geoff Holroyd, PhD
Chair, Beaverhill Bird Observatory
Research Scientist (retired) Canadian Wildlife Service

2

We used Teflon backpacks on NSWOs in 2009 with geolocators. I share your concerns about potential tag loss using Stretch Magic or similar single-strand unsheathed elastic, though some folks apparently have had good retention using leg-loops on saw-whets with the more traditional elastic beading cord that is a multi-strand elastic core in a nylon sheath. However, we also noted with concern the recent paper by Biles et al. (J. Raptor Research 2023, "Tracking device attachment methods for American Kestrels: Backpack versus leg-loop harnesses”) that found substantially lower annual return rates for American kestrels tagged using leg-loops vs. backpacks. We’ll be doing a large (250+ tag) saw-whet project starting next year in the Northeast and are leaning toward Spectra backpack harnesses.

Scott Weidensaul
Milton NH