Some population surveys are conducted during the spring and autumn migrations, such as the Mid-continent Sandhill Crane Survey and the Fall Inventory of Mid-continent White-fronted geese.
Mid-Continent Sandhill Crane Survey
Nearly the entire population of cranes gathers in Nebraska’s Platte River Valley during spring migration. A pilot-biologist and observer count birds along established transect lines. Aerial photography of a sub-sample of crane flocks is used to quantify errors and develop correction factors to obtain a more accurate population estimate. A Status and Harvests of Sandhill Cranes report is produced each year.
White-fronted Goose Survey
Another example of a migration survey is the Fall Inventory of Mid-Continent White-Fronted Geese that is conducted every September in the Canadian prairie, where the population gathers during the southward autumn migration.