Since some birds do have their full adult plumage by their first winter, they will likely be given an Adult annotation. This bird is the same age, but just hasn’t developed adult plumage yet, so is recognized as a youngster…
An “immature” option has been requested for birds but has not been implemented (discussion here: Let’s Talk Annotations).
Barring the addition of that option, “juvenile” is the most appropriate term in my opinion. Though many observers choose to leave annotations blank when the ideal terminology is not an option.
Just to clarify, these two individuals are not the same age. The first link is a Second-Year bird (it was born in Spring/Summer 2022, so is in its second calendar year of life and holds a formative plumage). The second link is an After Second-Year bird (meaning it was born in Spring/Summer 2021 or earlier and holds definitive adult plumage).
The way I interpreted this was the OP was not claiming the individuals in the two observations were the same age. They were saying that a hypothetical individual of a species that molts directly into their definitive (adult) plumage during their post-juvenile molt (e.g., Horned Lark) would be annotated as an adult in their first winter, while species that have a distinct, post-juvenile but pre-definitive (immature) plumage (e.g., White-crowned Sparrow) would be a “youngster” despite the two birds being the same age.
Thank you for the clarification, but I am not sure I understand. I thought I did point out that they are different ages. It seems as if you are saying the same thing I did. I called the first bird a First Winter bird and the second an adult based on plumage.
Exactly! Thank you for explaining. I don’t have the experience or knowledge to express my thoughts in the way that you did. You are an excellent interpreter of informal Citizen gibberish to formal Scientific language.
One option is to use an observation field rather than an annotation. Bird Plumage allows you to distinguish between four categories: natal, juvenile, subadult (immature), basic (adult non-breeding), and alternate (breeding) plumages.