2019 Northeastern Naturalist Notes Vol. 26, No. 2
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N. Perlut
Latest Documented Fall record of Oporornis agilis (Connecticut
Warbler) in North America
Noah Perlut*
Abstract - On 11 November 2017, a male hatch-year Oporornis agilis (Connecticut Warbler) was
killed by a Felis catus (Domestic Cat) in Scarborough, Cumberland County, ME. This specimen,
housed in the University of New England ornithological collection, is the latest documented fall
record of this species in North America.
During fall migration, Oporornis agilis (Wilson) (Connecticut Warbler) migrate south
and east from their breeding grounds to the eastern coast of North America before flying
over open ocean to islands in the eastern Caribbean and then to South America (McKinnon
et al. 2017). On 11 November 2017, a male hatch-year Connecticut Warbler was killed by a
Felis catus (L.) (Domestic Cat) near Thomas Drive, Scarborough, Cumberland County, ME
(latitude 43.5589°N, longitude 70.3200°W). To my knowledge, this is the latest verified fall
record of Connecticut Warbler in mainland North America, and is notably later than other
records for the northeastern US. The latest bird-banding capture of Connecticut Warbler at
equal or greater latitude in North America is 15 October (Alpena, Michigan; USGS 2018).
Peak frequency of reports along the east coast of the US is 15 September, with nearly all
migrants occurring from late August to late October (eBird 2018a).
Previously, the latest record for Maine was a sight record with photographs from 12
October 2015 in York County (eBird 2018b). From north to south, latest reported sight records
or banding records (USGS 2018) for this species include: Ontario 19 October (USGS
2018), Nova Scotia 18 October (McLaren 2012), New Hampshire 13 October (Keith and
Fox 2013), Vermont 21 October (eBird 2018c), Massachusetts 26 October (Veit and Petersen
1993), Rhode Island 27 October (USGS 2018), Connecticut 31 October (Zeranski
and Baptist 1990), New York 30 October (Levine 1998), New Jersey 31 October (USGS
2018), Delaware 24 October (Hess et al. 2000), Maryland 7 November (Stewart and Robbins
1958), Virginia 29 October (USGS 2018), and Bermuda 3 November (eBird 2018d).
Connecticut Warbler vacates mainland North America during winter (Pitocchelli et al.
2012). Although Christmas Bird Counts spanning 15–31 December from 1967 to 2013 have
reported the species 14 times (National Audubon Society 2018), none of those observations
is documented by a photograph, preserved specimen, or measurements. A banding report
for 16 November at Vero Beach, FL (USGS 2018), may constitute a later fall record than the
Maine bird, although this record is also not documented by a photograph or measurements.
Connecticut Warbler is frequently misidentified, especially in fall when immatures and females
can be confused with both Geothlypis philadelphia (Wilson) (Mourning Warbler) and
G. trichas (L.) (Common Yellowthroat) and vice versa. In fact, I originally misidentified
this bird as a Mourning Warbler, until more detailed study of its plumage and morphology
identified it as a Connecticut Warbler. Therefore, verifiable evidence in the form of a photograph
or specimen is often necessary to document extra-limital records and extreme dates
of occurrence.
*University of New England, Department of Environmental Studies, 11 Hills Beach Road, Biddeford,
ME 04005; nperlut@une.edu.
Manuscript Editor: Jeremy Kirchman
Notes of the Northeastern Naturalist, Issue 26/2, 2019
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2019 Northeastern Naturalist Notes Vol. 26, No. 2
N. Perlut
I made the following morphological measurements, which allowed diagnostic identification,
from the Maine specimen: wing chord = 67.5 mm, flattened wing length = 68 mm,
length of p9–length of p6 = 5.5 mm, tail = 49 mm, tarsus = 20.71 mm, bill width = 2.90
mm, bill length = 8.08 mm, bill depth = 3.16 mm, mass = 13.8 g, spread wing = 160 mm,
and total body length = 130 mm. I sexed the bird as male (testes present), and aged it as a
hatch-year in formative plumage (juvenile rectrices pointed; incomplete skull ossification).
The wing chord exceeded the known maximum for Mourning Warbler, and the p9–p6 difference
was likewise longer than known for Mourning Warbler (Lanyon and Bull 1967,
Pitocchelli et al. 2012). The Maine specimen shows a bold, whitish-buff eye ring combined
with a brownish buff throat cut off sharply at the breast, characteristic of the Connecticut
Warbler. The Mourning Warbler has, at most, a thin eye ring that is narrowly broken both
anteriorly and posteriorly, a yellow wash to the chin and throat, and lacks a sharp border
between throat and breast. A narrow break in the eye ring posteriorly behind the eye often
occurs on immature Connecticut Warblers, as was the case for the Maine bird. Its dull yellow
underparts also differed from the bright yellow typical of the Mourning Warbler. The
specimen is housed in the Department of Environmental Studies ornithology collection
at the University of New England, Biddeford, ME (reference identification: UNE 057). I
encourage others to make careful observations and measurements of this species, where
possible, to provide a more detailed understanding of the location and timing of movement
by Connecticut Warblers. Finally, this record serves as a continuing call to mediate the
impacts of free-ranging Domestic Cats on birds (e.g., Loss et al. 2013), including relatively
rare species like the Connecticut Warbler.
Acknowledgments. This work was supported by the University of New England. Major
thanks to L. Bevier, for his thoughtful support. E. White took all morphological measurements;
L. Moser prepared the specimen for the museum collection. CBC Data is provided
by National Audubon Society and through the generous efforts of Bird Studies Canada and
countless volunteers across the western hemisphere.
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