Morphological Cues to Identifying Age Cohorts in Crows

Definitions:

Fledgling: fully flighted (or nearly so); age between ~5 weeks and 2 months (early June through ~mid-July, depending on hatch date). typical weight: ~275-325 grams

Early Juvenile: late summer of hatching year, after juvenile body feather molt.

Late Juvenile: Autumn-early winter of hatching year (little different from early juvenile).

Yearling: by convention, all birthdays are on January 1 (all of this year’s juveniles are considered to be one year old on January 1 of next year, etc). typical weights: ~340 380 gm.

Sub-adult (second & third year; typically non-breeding birds): Technically still yearlings until January 1, but following their yearling molt in August, these birds are physically indistinguishable from breeding adults.

Adults: Four years-and older (up to ~17 in rare cases) and typically weighing ~390-470 grams (1 pound = 453 gram). Experienced observers can distinguish them from sub-adults by specific behaviors during breeding season and diabolically annoying “cageyness” in all seasons.

Note: some of the following characteristics (esp. eye color in juveniles and mouth color and (to lesser degree) wing & tail feathers in yearlings) can vary significantly between individuals, but as a general guide they work well. Click on photos to enlarge them then close window to return to this page. Note these are large pictures and make take a long time to load!

**Mouth and Tongue

**This document is also being used by PAWS (and other re-hab.) volunteers who are trained to handle injured, sick or dead birds.  We do not expect that most other people who find dead birds will be examining them closely enough to check out the inside of their mouths!  If you choose to bag a freshly dead bird for disposal or testing (see instructions on King County website) and can conveniently get a good look at its mouth, great.  Otherwise you may cheerfully ignore this cue.

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Photo 1

Photo 2

Photo 3

Fledgling/early juvenile: mouth and tongue bright pink; minimal black at tips of beak and tongue; note pink skin at “corners” of mouth joining upper and lower beak

Late juvenile/yearling/nonbreeding sub-adult: mouth lining still substantially pink, but with substantial black at sides; and on tongue; note that moth corners now grayish. Pink/Black mix is quite variable between individuals 

Breeding adult: Mouth and tongue mostly to completely black; a little pink or gray will remain at base of tongue or very back of mouth even on older adults but black clearly dominates after yearling molt.


Eyes, Body Feathers, and Beak “Hinge” Skin
[click on photos to enlarge, then close window to return here]

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Photo 4

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Photo 6

Fledgling: eyes baby blue, body feathers flat/charcoal black (not glossy—note contrast with wing feathers and compare photos 13 and 14), ears lightly feathered; pink skin at corner of mouth (beak “hinge”) is prominent.

Early juvenile: Eyes gradually darkening but typically not yet the dark brown of adults (photo 6); newly molted body feathers virtually identical to adult; full feathering at base of beak and ears, but distinctive pinkish beak hinge skin still visible, beak relatively thin

Late juvenile—adult: eyes dark brown, beak hinge skin black and minimal; in adults, esp. males like this one, beak is relatively thick and powerful. Breeding females will also have a bare "brood patch" on their abdomens until the August molt.

Wing and Tail Feathering

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Photo 7

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Photo 9

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Photo 12

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Photo 13

Photo 14

Tail:

Wings:

Photos 13 & 14: Note clearly visible fledgling beak hinge and contrast head, chest and back feathering between fledgling (photo 13) and adult (photo 14).

P.S.: Re photo 13—Don’t try this at home!