Since 2008, the Hummer/Bird Banding Research Collaborative has been studying the Northern Saw-whet Owl as a contributor to the Project Owlnet study. This is a continent-wide study which includes Canada. Until this study began in 1997, no one realized Saw-whet Owls migrated south of the northernmost states of the U.S. in large numbers.
By the autumn of 2013, HBRC will have three Saw-whet Owl studies operating five nights a week from dusk until about midnight from mid-October thru mid-December.
Each station is operated by a federally licensed bird bander and several volunteers.
The banders use a line of 12 meter fine, soft mist nets stretched through the woods, with a digital recording of the male saw-whet’s “toot” call playing at high volume near the nets. Passing owls are attracted by the call and caught in the nets, which are checked regularly through the night.
Once captured, each saw-whet is fitted with a lightweight, numbered aluminum leg band issued by the federal Bird Banding Lab. The owl is then aged, sexed, weighed and other information about their biology is recorded, all of which help us learn more about these secretive birds. Sometimes a feather is taken for DNA research, or to help disease specialists studying the spread of ailments like West Nile virus or Lyme disease.
Then the owl is released – and if it is ever captured again by another researcher, or found dead by the general public, the serial number on its band will help us learn more about the movements, lifespan and ecology of these owls. Each year, many of the owls captured by the HBRC banders have already been banded by other researchers, and many of the owls we band are subsequently reported.
Where are the Males?
One of the biggest mysteries about saw-whet owl migration is the scarcity of male saw-whets, which make up approximately 6 percent of the owls captured. So where are the males?
One possibility is that the audiolure the team uses – the tooting call of a male saw-whet – is simply more attractive to female owls, even though autumn is not the breeding season. But researchers in other areas, who used nets but no audiolure, also reported that they caught more females than males. It appears the lure is only part of the story.
One possibility is that adult male saw-whets stay on their breeding grounds year-round, leaving migration to females and young owls. If so, this would be a very unusual migration strategy among raptors, but there is some evidence for it. Almost all the males captured at the center’s banding stations are first-year owls, too young to breed – out of nearly 4,500 owls banded since 1997, only 40 have been adult males.
By marking a wild bird with a numbered leg band, scientists can uncover many of the remaining mysteries about their lives – where they travel, whether they return to the same places each summer and winter, whether they choose the same mates, and how long they live, among many other things.
Project Owlnet is a collaborative undertaking involving nearly 120 owl research stations across the U.S. and Canada, all working to better understand the movements and ecology of saw-whets and other migratory owls.
Owlnet was founded by David Brinker of Maryland’s Department of Natural Resources, and is coordinated by Brinker, Steve Huy of Maryland and NSCNA saw-whet project leader Scott Weidensaul.
The Owlnet website provides standard methodologies, techniques and approaches for scientists interested in conducting migration research, as well as an active listserve to allow participants to share their results, data and information on band recoveries.