Thursday, August 19, 2010

Summer Fledgling Photo Album

The Observatory's Monitoring Avian Productivity and Survivorship M.A.P.S. projects for this year have come to a close. From this summer's host of birds banded, we thought it would be of interest to show some examples of juvenile plumaged birds. Some species can be identified outright because of their closeness in appearance to adults of their species while others are not as obvious. Sparrows in particular can test your mind.

Take this hatching year (HY) Song Sparrow (SOSP) with the extra spots/streaks on its breast. HY Song Sparrows look much different than the familiar adults where the streaks come together in the middle to form the distinct breast spot field mark best known with this species.

Juvenile feathers differ in quality and are often identified as "loosely textured," as in those on the breast of the SOSP above. Juvenile feathers have the barbs on their shaft arranged farther apart creating the loosely textured appearance.

Hatching Year (HY) Grasshopper Sparrow (GRSP)
Note the loosely textured breast feathers.
Below you can see one of the best field characteristics of a GRSP: its flat head. Aren't the colors on this bird beautiful?! This individual was captured in the wooded marshes of our Navarre Marsh research station, not exactly the grassland habitat typical for this species, so you cannot always predict what habitat a bird may use.

Take a look at this confusing hatching year Chipping Sparrow (CHSP)
HY "Chippers" have a streaked breast, much different than the completely
plain breast of the adult.
By the time October rolls around, this bird will have lost the streaks on the breast and will resemble the winter plumaged adults.

Hatching Year Eastern Towhee (EATO)
Note the typical juvenile sparrow spots or streaks. However, there are other characteristics defining this bird as a hatching year bird. Eye color on this bird is a muddy red, where an adult EATO's eyes would be ruby red. This bird also has a visible yellow gape where the upper and lower mandible (bill) come together on the skull. Yellow gape is not a single good determining factor in concluding a hatching year bird as there are some species which continue to have a
yellowish gape as an adult.

This hatching year Marsh Wren (MAWR) will undergo
two molts before next spring.
Replacing many of its feathers twice is an expensive energy endeavor, but this is what evolution has designed in order to maintain its feathers in the rough wetland habitats. Most birds only undergo a partial molt in late winter, replacing their body and contour feathers but not their flight feathers. You can see the juvenile feather structure and the presence of a gape on the bird above. However, wrens usually keep this fleshy gape throughout their lives.

The back of this HY Marsh Wren (MAWR) lacks the
characteristic dark triangle of the adult.
It is too dark in coloration to be a Sedge Wren (SEWR) and this bird shows
the faint eyebrow that MAWR exhibits.

Take a look at this Blue Jay (BLJA) with the same loosely textured
juvenile feathers and fleshy gape.

Some birds, like this Eastern Wood-Pewee (EAWP), are not as obviously different
in their juvenile plumage from the adults.
Note the buffy coloration of the wing bars indicating a HY. Pewees and Empidonax flycatchers possess this HY characteristic in fall.

Body molt in birds occurs in feather tracts that occur longitudinally down their breast and back. It is apparent here on this molting HY Northern Cardinal (NOCA).

You can determine the sex of a NOCA once this molt begins. Note also the dark bill coloration which assists in determining it as a HY bird.

This HY Yellow Warbler (YWAR) is molting but still shows the whitish downy feathers down the center of its breast from its juvenile plumage.

Eye color, spotted breasts, loosely textured feathers, over accentuated gape, and lighter or darker bill coloration are good indicators of HY birds.

Here are a few for you to identify!

Well, how did you do? If you answered: Gray Catbird (GRCA), Brown Thrasher (BRTH), and American Robin (AMRO), then you know your youngsters!

There is no quiet time for the bird bander. With summer breeding bird surveys safely in the books, we will be starting fall migration soon. This will be an important fall as we watch for potential population ramifications following last spring's low bird numbers. BSBO will keep you informed of migration from every perspective. Follow us here on the Bander's Blog, on the BSBO research pages, and on Kenn Kaufman's Birding the Crane Creek - Magee Birding, for all the latest information on fall migration.

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