Once a bird is captured, the species is determined and certain data on each individual is recorded.
Data collected includes species, date captured, age, measurement of the wing chord, and gender if it can be determined. Age determination can be difficult, as can gender. Age categories include hatch year (HY), after hatch year (AHY), second year (SY) and after second year (ASY). AHY is used for birds that don't have marked plumage changes after they molt into their adult feathers. SY is used in species like American goldfinches, where the feathers at the bend of the wing are paler in the second year than in subsequent years. ASY is used for birds like purple finch males, that don't get their purple coloring until after their second year.
Gender can also be difficult to tell depending on the species so there are three categories: M, F, and U (for undetermined). In spring it's sometimes possible to determine the gender of birds such as chickadees by looking for a brood patch. The female's brood patch is a very extensive bald spot on the breast that can be detected by blowing lightly on the feathers. The male's is less extensive and not as bald. So we were able to determine gender at this banding by brood patch, where the chickadees banded at the end of March were all listed as U.
Band is chosen according to size for each species, and the number is recorded before it's attached to the bird. Sometimes it's hard to make out the numbers:
We have a leucistic purple finch in the area. He's quite distinctive. Leucism is a condition in some birds often referred to erroneously as 'partial albinism'. The birds aren't true albinos, but do have a defective pigment metabolism. 'Mr. Pink' was caught and banded on Tuesday, and our identification as a purple finch was confirmed after some discussion and examination by the banding crew.