Tuesday, January 4, 2011

Tracking the Saw-whet

Our fall monitoring project has expanded to have a new component- radio telemetry and tracking. I am helping a CSU graduate student Julie Shaw, with her studies to determine winter roost sites of the saw-whet. One of our questions derived from the fall monitoring was, "where do the birds go in the winter after migrating through the Reserve?" We knew that some stayed

on the Reserve because we recaptured a few, a couple of weeks to
months later.

But now, because we have installed tiny radio transmitters on the owls (3 grams total, less than 3% of the birds body weight-see picture above that includes radio and harness material), we are able to track them to their actual locations! Julie will collect 2 years of data and then publish her results, brand new information for our region- and wonderful to better understand the ecology of our population of owls! So far we have found owls roosting on the ground like this bird,

some a few feet off the ground, and many way up in a tree- up to 85 feet, so all we see is a feathery ball, like in the picture (the bird is within the red circle).

We always like to get a good look if possible to check the condition of them and make sure their harness is fitting well. The harness will come off in about 3 months- the same time as the life of the radio battery. Most of the birds sit in good cover to protect themselves from diurnal predators like Cooper's Hawks. We got a really nice look at this bird who has had her transmitter on for 8 weeks.

Julie has been great about creating maps of the bird's locations, like this one. Here you can see a map with 4 different roost locations of one bird who was banded at the Reserve and then moved
down into Bidwell Park.

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