Distance and bearing were calculated using equations in Cowardin (1977), where:
Note: if Southern Hemisphere, set latitude to negative
if Eastern Hemisphere, set longitude to negative
if P > 180, then set P = P – 180
Distance (D) between banding and encounter in
degrees was calculated as:
The bearing (C) was calculated as:
Encounters fitting into the categories marked with a D below were considered "direct" recoveries, whereas all others were considered "indirect."
Note that direct recoveries include birds assumed to be dead (including those with "unknown" present condition) plus all birds encountered at the site of banding within 90 days.