Sunday, August 29, 2010

Fall Migration Highlights for the Week of August 23-29th

Posted by Julie Shieldcastle, Navarre Songbird Migration Station Supervisor:
The first week of Migration Songbird Monitoring produced a few exciting highlights for the week. These included our first Yellow-billed Cuckoo for the year. We heard them occasionally during spring and summer but none were slow enough to get into the nets to be banded. Another highlight was the 18 warbler species captured in the first week! These included: Tennessee, Nashville, Chestnut-sided, Magnolia, Black-throated Blue, Black-throated Green, Bay-breasted, Blackpoll, Black-and-white, American Redstart, Prothonotary, Ovenbird, Northern Waterthrush, Connecticut, Mourning, Common Yellowthroat, Wilson’s, and Canada. It's worth noting that there has not been a Yellow Warbler (YWAR) seen or heard on the research site since mid-August. It appears that the resident YWARs have left the area.

Here are some pictures of a few early migrating warblers just in case you do not have a chance to get out and enjoy them:

Wilson's Warbler (WIWA)

Chestnut-sided Warbler (CSWA)

A weak front came through on Thursday and turned the winds to the NW which produced a small movement of birds on Friday and Saturday. The coming week looks to be good after Thursday when another front is slated to come through and temps are to drop to the low 80’s.

We were able to set up the five beach nets in addition to the main migration station nets this week. As usual, the beach nets caught higher numbers of Warbling Vireos (WAVI) than the nets inside the dike at the main station. Twelve out of the 14 WAVIs captured were caught in the five beach nets versus two in the 23 inside nets. This is a species that appears to be favoring habitats immediately along the lake shore instead of the larger older ridge habitat just a few yards inside the dike.

Warbling Vireo
Another highlight Saturday was capturing two Connecticut Warblers (CONW).

One was an adult male with its gray head and distinctive eye ring that really does stand out and go “Boing!" The other is a hatching year bird of unknown sex with a distinctive eye ring that looks similar to what a female CONW eye ring looks like. Hatching year birds generally can't be sexed with certainty. Even so, these are gorgeous birds no matter what their plumage!

Since Saturday was an exceptional day for warblers, I thought it would be great to take a group photo of eye ring warblers. The only one I wanted that was missing was the Chestnut-sided. Look at the photo of the CSWA above and you'll understand why it would have fit into the group photo. Can you identify all the eye ring birds? (Answer below).

Three other favorite birds of the week I would like to share are these:

Tennessee Warbler

Just look at the green on this bird! The TEWA is the only warbler I know that has this chartreuse green coloring. Note the white undertail coverts which distinguishes TEWA from its cousin the Orange-crowned Warbler (OCWA), which has yellow undertail coverts.

This bird was a perfect example of an adult female Black-throated Green Warbler (BTNW).

Here is the male warbler that remains black, blue, and white in every plumage, the Black-throated Blue Warbler.
Isn't he a handsome bird?! This particular bird is a hatching-year with his green-edged primary coverts.
Otherwise he looks like an adult male in coloration.

Enjoy the early fall migrating birds. There are still some Baltimore Orioles (BAOR) singing as well as flycatchers and you may catch a glimpse of the last of the golden Prothonotary Warblers before they head south!

Answer to the eye ring bird quiz: From left to right: Magnolia Warbler (MAWA), Nashville Warbler (NAWA), Ovenbird (OVEN), and Connecticut Warbler (CONW).

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.

Tuesday, August 3, 2010

Connecticut Warbler in Ohio - In July

Posted by Mark Shieldcastle, BSBO Research Director: The more we study birds the more we realize we have a lot to learn. There is so much more out there than what we see in our “normal field of view”. Binoculars and field guides revolutionized our knowledge of birds but maybe no other tool has done more than the act of capture and marking birds. Banding has taken ornithology to heights that could not be reached without this simple but powerful technique. Case in point, the special visitor to the Navarre Banding Station on 25 July.
Each summer, following the exhaustive spring migration study, BSBO researchers begin breeding bird banding projects. These studies, part of the Monitoring Avian Productivity and Survivorship (MAPS) program begin in early June and continue into early August with field work once in each 10 day period. In Navarre, to coincide with this operation, we also operate the main migration station simultaneously after the 1st of July. It was here we had our surprise guest in the nets. One of three birds captured in the first round was an adult female Connecticut Warbler (CONW).

This bird was in full molt and looking quite ragged. Extensive measurements were taken for verification of species, sex, and age, including an unmistakable brood patch. The brood patch was representative of those we are seeing on Yellow Warblers (YWAR) and Common Yellowthroats (COYE) at this time. Our Connecticut female appeared similar to those following young around or having recently left young.

To facilitate field recording of bird names, alpha codes were developed by the Bird Banding Laboratory for every bird species in North America; no two can be the same. For species with two parts to their name the general rule is to use the first two letters in each part of its name. However, the Connecticut Warbler represents one of the exceptions to this rule. Can you guess why? The answer will be revealed at the end of this post!

Bird showing symmetrical molt

CONW has a pointed wing with p9 (9th primary) longer than p6, while the rounded wing of a MOWA has p6 longer than p9 in most all birds.

Photo shows undertail coverts vs. tail length (useful in separating from MOWA)

What is the significance of this little visitor? For one, it is most likely the first of its kind ever recorded in Ohio during July. Second, with its breeding condition, could it have nested here? Third, is most perplexing, if not a breeder here, why so different than what is known of this species biology? Granted, how much is really known about the CONW? Maybe a little more than one might think.

The species is one of the latest spring migrating warblers with similar behavior in the fall: fall migration beginning in late August from its breeding grounds. Peak migration in Ohio is reported in the literature as mid-September to early-October with no reports earlier than the last week of August. Nesting is documented as June into July with fledging late July. The summer adult Pre-basic molt is reported to occur July to August PRIOR TO MIGRATION.

There are two different molt strategies employed by our warblers each summer. Most, like the CONW and the Magnolia Warbler (MAWA), complete the molt prior to starting migration while others like the Tennessee Warbler (TEWA) and Chestnut-sided Warbler (CSWA) start prior to migration but may continue as they migrate south.

So why is it here now, in July, when by all accounts it should be at the closest the very northern reaches of Lower Michigan? Let’s throw out some possible scenarios to consider:

1) It did in fact nest here in Navarre; or at least tried to. Was there also a male CONW that stayed? We did have individuals singing until the end of May. Or did it stay with a male Mourning Warbler (MOWA)? We have documented males of this species the past two years on territory throughout June. Was it injured or sick resulting in an abnormal migration? Still, that was one good brood patch. Did the Buttonbush swamp in Navarre fit the “bog nesting criteria needed”?

2) It did try to nest somewhere reasonably close, failed, and dispersed to the Lake Erie marshes prior to fall migration. This is being observed in a wide range of passerines such as orioles, phoebes, and maybe even the YWAR where we capture large numbers of young. It does appear this behavior is primarily of hatching year birds. There is no indication in the literature of such a “dispersal migration” in adult birds of this species. We had a similar situation a few years back with a Worm-eating Warbler (WEWA) female. We’re not thought to be part of breeding range for this species either. The big difference is the majority of the WEWA range is south of the marshes which would fit a northward post breeding movement that is documented in a wide range of species but not a pre-migration southward movement from a more northern breeder.

3) A third possibility is that this bird either represents a behavior we just don’t know about or one that defies all known literature and left not only a month early but also violates known biology of the molt sequence of the species.

Will we ever know the truth about this encounter? Maybe not. The only way to be as close to “sure” as we can hope to be is by catching the young as well. Only banding may shed light on this interesting feathered friend.

If you want to learn more on the role of banding over the past century+, join us at the Inland Bird Banding Association meeting we are hosting October 29-31. Learn more here: Black Swamp Bird Observatory

To answer the question regarding exceptions to the alpha code rule: COWA cannot be used for Connecticut Warbler (CONW) because of the Colima Warbler (COLW).

Curson, J., D. Quinn, and D. Beadle. 1994. Warblers of the Americas: an identification guide. Houghton Mifflin Co., New York.

Pitocchelli,J., J. Bouchie, and D. Jones. 1997. Connecticut Warbler (Oporornis agilis). In The Birds of North America, No. 320 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists’ Union, Washington, D.C.

Pyle, P. 1997. Identification Guide to North American Birds. Part I. Slate Creek Press. Bolinas, CA.