Fri-D: How to Talk About Age in Birds

[Yellow-rumped Warbler, Cape May, NJ October 21, 2012. Click to enlarge all photos. First winter. Also correct: first fall, first basic, first cycle, hatch year (HY), formative, and immature.]

Roger Tory Peterson once said something to the effect of "... it is important to know the names of birds because we are then able to speak properly about them." Amen, and this goes for the names of bird plumages and bird ages. At the end of this post you will find a chart of the ways one might speak properly about bird plumages and ages. I believe this is often made more complicated than it needs to be, in part because each field guide makes up its own rules. I like and generally follow what the Sibley guides do; I particularly like that David also tells you what months you generally see a given plumage. Let's start with a concrete example: the oh-so-familiar Yellow-rumped Warbler.

[This would be a picture of a juvenile Yellow-rumped Warbler, except I don't have one, because like other songbirds Yellow-rumped Warblers dump their juvenal plumage early (the plumage is juvenal, the bird is a juvenile, one more unnecessary complication). Songbirds molt into their first winter plumage rapidly and often are secretive while they're doing it. Since Yellow-rumpeds don't breed where I do most of my birding, other than a precious few in Sussex and Passaic Counties, NJ, you'll have to look juvie Yellow-rumped up. By the way, when I say "dump," I mean molt, i.e. drop feathers and replace them with new ones. The only other way birds can change the appearance of their feathers (other than accidental staining) is through wear, which some do on purpose, like European Starlings or meadowlarks.]



[First winter Yellow-rumped Warbler, November in Cape May. Since it's fall, you can call it first fall if you want, but it's the same feathers they'll have until spring. Sometimes I don't feel sure whether a given bird is a first winter or drab adult winter.]

[Adult winter Yellow-rumped Warbler. Brighter yellow splotches below, more cleanly marked than first winter, I see many I'm not really sure of the age on.]

[Adult breeding Yellow-rumped Warbler. April, Cape May. This plumage is attained by a head and body molt in late winter and spring, we'll be seeing these in a few weeks. As noted in the chart below, in the field it's often impossible to tell first breeding/summer from adult breeding in the field. I actually think this is a first breeding, because the tail feathers look more pointed than truncated and the flight feathers look a little too worn, but this is tricky even in the hand.]

Next Fri-D we'll have some fun with gulls . . .

Plumage Terms for Birds
© Donald Peter Freiday

Don’s Favorite Term	Approximate Age (varies greatly by species; big birds generally take longer)	Humphrey-Parkes	Cycle	Banding
Nestling (still in the nest, may be naked, downy, partially feathered, or fully feathered)	0-14 weeks		1st cycle once it’s got some real feathers	HY (Hatch Year)
Fledgling (can fly, wears normal feathers, cared for by parents)	2-18 weeks		1st cycle	HY
Juvenile (fully feathered, usually independent)	2 weeks- 4 ½  months	Juvenile	1st cycle	HY
1st winter (you can say 1st fall if it’s fall, but it’s the same feathers as it will have in winter)	2 weeks – 9 months	1st basic	1st cycle	HY Formative plumage; After January 1, AHY (After HY) or SY (Second Year) if you can tell
1st summer or, for many, adult breeding (1st summers often cannot be told from adults in the field, usually can tell in the hand by feather wear, molt limits, feather shape)	4-12 months	1st alternate	1st cycle	SY or AHY
Adult winter	12-19 months	Definitive basic	2nd cycle	SY or AHY; after January 1, TY (3rd year) if you can tell, or ASY or AHY
Adult breeding Repeat adult plumages in future,	19-24 months	Definitive alternate	2nd cycle	TY or ASY or AHY
BUT SOME SPECIES	TAKE	LONGER	THAN	TWO YEARS TO ADULTHOOD