The poet, Ogden Nash, humorously wrote about how difficult it is to identify birds in his poem “Up From The Egg.” He mentions that even after finally being able to identify a bird it changes its plumage writing…”then it goes and changes its plumage, which plunges you back to ignorant ‘gloomage’…” This is true but what he doesn’t say is that juvenile birds take weeks, months and sometimes even a year to molt to adult plumage. I have shown in previous posts that some birds such as longspurs wear the tips of their feathers, not a true molt, resulting in a fresh and brightly colored breeding plumage whereas some birds suspend their molts until reaching their wintering grounds. These birds show a combination of adult and juvenile feathers if caught at the banding station.
Above is one of the most common migrant birds of the Chico, Chipping Sparrow. In the fall many of the Chipping Sparrows caught and banded are juveniles and their plumage is different than it is when they become adults. At the left is an adult Chipping Sparrow as it looks in April and May. On the right is a juvenile bird as it appears in September and October. Making the identification even more difficult is the Chipping Sparrow genus, Spizella, has three other members passing through the Chico at varying ages and some of the juvenile birds are very difficult to identify. Beginning birders sometimes ignore looking at sparrows and some may just call them LBJs, little brown jobs.