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Chester River


Field Research Station

Northern Saw-whet Owl Monitoring

In the Fall of 2007 we learned a Northern Saw-whet Owl irruption was expected in the eastern United States. An irruption is a periodic movement of a species, generally due to food supplies or habitat availability. In years with great breeding success, there are too many Saw-whets to live off the resources available in the north and so large numbers of the owls migrate south in search of a place with adequate prey to spend the winter. A little research led us to Project Owlnet, a network of North American owl banders focusing on Saw-whet Owls. From this group we learned the protocols used to monitor Saw-whet migration.

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A small number of nets are run at night during late October and November and we play a standardized audio lure to attract owls. During Saw-whet Owl banding we have captured Eastern Screech Owls, and we have heard (but not yet caught) Barred Owls and Great Horned Owls in the woods.

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Owl feathers contain a pigment called porphyrin which glows in ultraviolet light. This pigment fades over time so the brightness of the pink glow can be used to age feathers and the bird, with pinkest being newest. The owl shown has a mix of young and old feathers.

Our Northern Saw-whet banding project contributes data to a continent-wide study of owl migration and distribution. These data can be pooled to help monitor population trends across North America.

You can track the number of Saw-whet Owls banded each fall by checking out the recent banding data.