Checklist S116686244
Sharing links
Totals
Observations
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Number observed: 8
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Number observed: 1
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Number observed: 4
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Number observed: 2
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Number observed: 1
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Number observed: 1
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Number observed: 2
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Number observed: 3
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Number observed: 2
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Number observed: 1
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Number observed: 3
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Number observed: 3
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Number observed: 1
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Number observed: 2
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Number observed: 2
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Number observed: 1
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Number observed: 3
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Number observed: 10
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Number observed: 3
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Number observed: 6
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Number observed: 6
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Number observed: 25
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Number observed: 35
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Number observed: 2
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Number observed: 1
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Number observed: 2
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Number observed: 3
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Number observed: 1
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Number observed: 10
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Number observed: 12
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Number observed: 1
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Number observed: 2
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Number observed: 3
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Number observed: 8
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Number observed: 2
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Number observed: 5
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Number observed: 4
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Number observed: 8
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Number observed: 1
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Number observed: 6
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Number observed: 10
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Number observed: 2
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Number observed: 5
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Number observed: 8
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Number observed: 4
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Lawrence's Warbler (hybrid)
Number observed: 1Details
Black mask and black bib. All yellow below. White wingbars. Popped up only briefly, but wonderful to see, particularly given this hybrid is much rarer outside of spring and early summer in Massachusetts, though some of that could be due to lower detection probability given that many spring and early summer birds are presumably located by song. Only some very poor photos.
Media
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Number observed: 3
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Number observed: 2
Details
Very exciting to see these two birds (and the Northern Parula) given that they represent a different class of migrants—“molt migrants”—meaning they have left their breeding grounds to undergo their pre-basic (i.e., post-breeding) molt of their flight feathers in a different location. To my knowledge, Tennessee Warblers do not breed much farther south than northern parts of New York/Vermont/New Hampshire. These two birds were well into their pre-basic molt. Both were molting their primaries and tail feathers. This is visible in the photos as a gap between the primaries where one or two of the feathers can be seen growing in. It also makes for a large “step” in the order of the primary tips. The molt is symmetric (rather than adventitious) since the gaps were present on both sides of the birds, meaning this was not an accidental loss of feathers. In addition, both birds were molting most of their tail feathers. Appears there is a fair amount of head, body, and covert molt going on as well. Molt migration is common and well-studied in some species groups (e.g., ducks), but a recent paper (Pyle et al., 2018) highlighted that there is likely much more of this molt migration happening in eastern land birds, which were previously thought to molt mostly on the breeding grounds. This sighting fits in nicely with their general findings. In most species, the molt of flight feathers and active migration typically don’t happen at the same time because growing feathers and migrating are both energy intensive processes, and gaps in the flight feathers impacts flight performance. However, apparently some species, including some wood warblers may molt feathers continuously in migration (Tonra and Reudink, 2018). It would be interesting to know which is the case for these birds.
We often think of birds like these prior to the end of August as “early migrants,” but perhaps it is better to say these birds are right on time for the phase of the annual cycle they’re going through (pre-basic molt). Always inspires me and builds a sentiment of respect to learn how complex and interesting these birds' lives are.
Here are some other nice molt migrant sightings of Tennessee Warblers and Northern Parulas undergoing flight feather molt in Western Mass in August, including another Tennessee that Larry Therrien found in Ware just a few days ago:
https://ebird.org/view/checklist/S59218816
https://ebird.org/view/checklist/S58764440
https://ebird.org/checklist/S116551518
Pyle, Peter, James F. Saracco, and David F. DeSante. 2018. “Evidence of Widespread Movements from Breeding to Molting Grounds by North American Landbirds.” The Auk 135 (3): 506–20. https://doi.org/10.1642/AUK-17-201.1.
Tonra, Christopher M., and Matthew W. Reudink. 2018. “Expanding the Traditional Definition of Molt-Migration.” The Auk 135 (4): 1123–32. https://doi.org/10.1642/AUK-17-187.1.Media
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Number observed: 4
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Number observed: 4
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Number observed: 1
Details
A male. Symmetric molt in the tail feathers suggests a molt migrant but I didn’t get very good looks or pictures of the wings. Looks like head, body, and covert molt as well. Likely a second bird in the area.
Media
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Number observed: 1
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Number observed: 4
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Number observed: 2
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Number observed: 1
Details
Long wings with white spots. Erratic flight. On the early side.