There are a lot of juveniles roaming our neighborhood yards. And, not just basketball & lacrosse pickup games. Birds too.
Juvenile birds are individuals that have molted to their first real plumage, but not their adult plumage.
Fledglings are juveniles. When they transition officially to juvenile status is, the best I can tell, a judgement call. I’m making the call for the birds below based on their plumage and being out on their own foraging, even if under the watchful eye of their parents.
To make Summer and Fall identification fun, some male juveniles have a plumage similar or identical to females.
Immature individuals have molted to their from their 1st real plumage to their 2nd or 3rd or 4th or more plumages before fully reaching their adult plumage. Gulls are examples of species that take 4-5 years to reach full adulthood plumage. Gulls are notoriously difficult except for full-on adults in breeding plumage.
Immature Bald Eagles are brown & tans and at a distance easily confused with hawks.
The bluebird juveniles are interesting. Juveniles from the first brood of the season will occasionally help out with parenting of the second brood.
Brown Thrashers in our yard are very interesting. This is anecdotal, but my observations have me thinking that they stay together as a family longer and learn from a lot from parental oversight. They also learn from the tried and true trial and error.