Thursday, September 10, 2015

Fall Passerine Migration Commences in the Lake Erie Marsh Region

The Navarre Migration Banding Station began the daily 2015 fall season on August 17th. From then until Labor Day weekend, 22 species of Warbler were captured, which is quite good for this early in the migration. August and Early September represent the return south of migrant Yellow (YEWA) and Prothonotary Warblers (PROW), Baltimore Orioles (BAOR), and Flycatchers as well as the staging locally raised birds of these species.

The August warblers included Ovenbird (OVEN), Northern Waterthrush (NOWA), Golden-wing (GWWA), Black-and-White (BAWW), Prothonotary, Tennessee (TEWA), Nashville (NAWA), Connecticut (CONW), Mourning (MOWA), Common Yellowthroat (COYE), American Redstart (AMRE), Cape May (CMWA), Magnolia (MAWA), Bay-breasted (BBWA), Blackburnian (BLBW), Yellow, Chestnut-sided (CSWA), Blackpoll (BLPW), Black-throated Blue (BTBW), Western Palm (WPWA), Canada (CAWA), and Wilson's (WIWA) warblers.

Connecticut Warbler
As we begin September, Blackpoll Warblers and Swainson's Thrushes are picking up in numbers. Warbler diversity will be increasing as we traverse September.

An advantage to birds in the hand is the ability to gather demographics on species captured. This permits the determination the age of all birds and the sex of many. However, birds still sporting some of the juvenile plumage, such as these Song Sparrows (SOSP), could have their age determined in the field as well. The juvenile and basic plumage of the chest and face of these two separate Hatching Year (HY) bird and After Hatching Year bird (AHY). The loose feathers of the HY bird are noticeable with no real central chest spot in juvenile plumage. 
AHY Song Sparrow (left) and HY Song Sparrow (right)

AHY Song Sparrow (left) note spotted breast.
HY Song Sparrow (right) with loose, yellowish/tan juvenile feathers
Bill coloration is another way to determine age for many species at this time of year. Here are two female Baltimore Orioles (BAOR). Note the lower mandible is all slate gray in the AHY bird and pink or lighter in coloration for the HY bird. This would not be quite as noticeable in the field.
HY Baltimore Oriole
Note the pinkish lower mandible

AHY Baltimore Oriole
Note the slate-colored lower mandible.
In Empidonax flycatchers, HY birds have olive to buffy edged wingbars. But this Eastern Wood Pewee (EAWP) (which is not an Empidonax) also carries the same colored wing bars, a clear indication of a HY bird. 
Eastern Wood Pewee
Note the lack of a distinct eye ring and the bi-colored beak unlike Empidonax flycatchers
which have obvious eye rings. (Eastern Phoebe has an all dark beak.)
Hatching-year Eastern Wood Pewee
Note buffy olive-edged wing bars. 
Sitting with an open mouth, a typical behavior of flycatchers in the hand, allows the opportunity to observe the bright mouth lining.
Back of Eastern Wood Pewee
Note the buffy-edged upper tail coverts as well as buffy wing bars which is definitive of a HY bird.
Confusing as some of the fall warblers may be, getting to know slight differences is important to becoming a better observer. These two birds are often mistaken for one another. However, they are of different sizes and very different throat coloration.
Here are two quiz birds that often trip birders up in the field. They look similar (especially in the field), but note the size difference, and the difference in the coloration of the throat.

Mourning Warbler (left) and Common Yellowthroat (right)
Again, note the size difference. 
Hatching-year Common Yellowthroat
 Note the strong yellow throat. Up close it may look like a lighter colored eye ring but from a distance that will disappear or be less apparent.
Mourning Warbler
Larger than the COYE, the split eye ring may look similar on some fall COYEs.
Note the throat and chest of this MOWA are gray. The throat on a COYE is yellow.
Fall Warblers can be a bit daunting, but with time and repetition observing the field marks you can figure them out (at  least most of them).
Good luck!
Free Public Songbird Banding Demonstration at the Observatory on Saturday September 26th at 10:00 AM.

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