Sensitive resettable odometer aids roadside census of red-winged blackbirds

A sensitive resettable odometer reading to 0.01 mile facilitated censusing breeding male redwinged blackbirds (Agelaius phoeniceus) from a vehicle. Territorial males along roadsides were 'marked' with recorded mileage readings rather than with landmarks of the types employed by Hewitt for censuses based on the Lincoln index principle. Sensitive odometers that can be reset have many potential uses in wildlife investigations.