A practical guide to bird watching in Sonoma County, California

(Unless otherwise indicated, all phone numbers are in the 707 area code)


Primary extension or primary projection

Primary extension or primary projection is a trait useful in distinguishing some groups of very similar birds. Primary extension is the distance from the end of the primaries in the folded wing of a bird to the end of the longest secondaries or tertials. It is often used by local birders particularly in arguing about whether a given bird is a Western Wood-Pewee (Contopus sordidulus) or a Willow Flycatcher (Empidonax traillii ). Useful in identifying some of the gulls as well. A long primary extension can make a bird's tail seem short. A short primary extension can have the opposite effect.


© Colin Talcroft, 2009, 2010, 2011, 2012.

Unless noted, all photos by the author. If you would like to use one of my images, please ask for permission for non-commercial use with proper credit or commercial use with proper compensation.


Long primary extension: Western Wood-Pewee, Spring Lake, Santa Rosa, September 17, 2012

Short primary extension: Willow Flycatcher, Spring Lake, Santa Rosa, September 17, 2012