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smittyone@cox.net

Terminology questions

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I had a HY female Common Yellowthroat and a AHY male Common Yellowthroat identified on here earlier today.  I'm confused over the terminology of Hatch Year and After Hatch Year..  Just as I still struggle with juvenile vs. immature birds, now I have this to contend with.  I "kind of" understand "First Summer" birds.  In that they won't be considered adults until their 2nd Summer (I think).  Take 1st Summer Orchard Orioles for example.  Wouldn't they still be considered immature?  Isn't a HY bird considered an immature bird?    

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@Tony Leukering will probably be able to give you an exact definition, but I think of it as this. A Hatch Year bird is a bird that has hatched this spring, and has not yet lived a full year. An AHY bird has lived a full year. As for the First Summer, AFS, juvenile and immature, I believe they have to do with molt cycles, which can be different for every species. 

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Despite what you just said, I believe it goes like this (subject to correction):

HY: Hatched in 2020.  (No one is so literal-minded that they won't understand how to apply this definition next year.)

AHY: Hatched in 2019 or earlier.  Birds become AHY on Jan. 1, sort of like racehorses.

 

Juvenile: In its first set of real feathers (not all down).

Immature: At least one non-juvenile feather has come in, but the bird is not in full adult plumage yet.  Some birds have a few years of immature plumages.

Adult: In a plumage that will be repeated more or less exactly next year (if the bird survives).

 

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I like the way my bird guide puts it:

"Juvenile birds (birds in juvenal plumage) are wearing their first true coat of feathers, the ones in which they usually fledge (leave the nest). Some young birds hold their juvenal plumage only a few weeks, while others such as true hawks, loons, and many other waterbirds hold their juvenal plumage into the winter, or even the following spring.

Most species replace their juvenal plumage in late summer or early fall with a partial molt into this plumage, usually while retaining the major, juvenal wing and tail feathers. All plumages between juvenal and adult are immature, an imprecise term. The sequence of immature plumages may continue for some years until adult plumage is attained. 

Birds are adult when their molts produce a stable cycle of identical (or definitive) plumages that repeats for the rest of their lives. Most adult birds have either one complete molt per year or one partial and one complete molt per year."

Source: National Geographic Complete Birds of North America (second edition)

Basically just elaborating on what @Jerry Friedman said.

 

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On 9/14/2020 at 10:47 PM, smittyone@cox.net said:

I had a HY female Common Yellowthroat and a AHY male Common Yellowthroat identified on here earlier today.  I'm confused over the terminology of Hatch Year and After Hatch Year..  Just as I still struggle with juvenile vs. immature birds, now I have this to contend with.  I "kind of" understand "First Summer" birds.  In that they won't be considered adults until their 2nd Summer (I think).  Take 1st Summer Orchard Orioles for example.  Wouldn't they still be considered immature?  Isn't a HY bird considered an immature bird?    

For most birds of most bird species in the northern hemisphere, the distinction of HY vs. AHY is simple. HY indicates any bird that was hatched in the calendar year being discussed, for whatever year is being referenced (usually, the current one). AHY indicates a bird hatched in a year prior to the current year, whether one year prior or 35 years prior. Once 1 January rolls around, the "ages" change. This system breaks down with crossbills and many southern-hemisphere-breeding species. It is possible in such species for individuals to hatch on 31 December and then change "age" the next day, making this age system -- which was designed for the US-Canada bird-banding system with the usual northern-hempisphere-centric viewpoint -- less than useful.

[Crossbills can be stimulated to breed by large food crops, but they are generally winter breeders. In times and places with truly massive food crops, juveniles only recently hatched can breed.]

The biggest problem that birders seem to have with ageing terminology is that, except for the HY/SY/TY/AHY system, bird ages are plumage-based, not calendar-based. There is nothing magical about 1 January. Except those bird banders that have to deal with the North American birding-banding system, I encourage birders to not use the calendar-year system and learn the modified Humprey-Parkes plumage-based ageing system, which divorces bird ages from the confounding effects of the calendar.

https://cobirds.org/Publications/ColoradoBirds/InTheScope/24.pdf

https://cobirds.org/Publications/ColoradoBirds/InTheScope/87.pdf

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