The Auk 112(2):510-511, 1995
Carnegie Museum of Natural History, 4400 Forbes Avenue,
Pittsburgh, Pennsylvania 15213, USA
An immature male wood-warbler netted north of
Ocean City, Maryland, on 17 September 1965 was
described by Short and Robbins (1967), and identified
by them as "an apparent hybrid Northern Water-
thrush (Seiurus noveboracensis) x Blackpoll Warbler
(Dendroica striata)." I have examined this specimen
(U.S. National Museum no. 481595) and agree that
one of the parents was undoubtedly a Northern Wa-
terthrush. However, I believe that the characters dis-
played by the hybrid agree more with a hypothesis
of parentage by a Cape May Warbler (Dendroica tigrina)
rather than a Blackpoll Warbler.
Short and Robbins (1967) briefly considered two
species of Dendroica other than D. striata as possible
parents of the hybrid, namely the Palm Warbler (D.
palmarum) and Cape May Warbler. They stated that
the hybrid "resembles an immature Cape May War-
bier in breast streaking and breast color, but the hy-
brid's larger size, differently shaped bill, lack of neck
markings, and absence of any indication of a yellow
rump patch seem to rule out that species as one of
the parents." I see no reason to invoke the size of the
hybrid as an indication of the Dendroica parentage;
although the Blackpoll Warbler is indeed larger than
the Cape May Warbler, there is no reason not to at-
tribute the large size of the hybrid to the waterthrush
parent. I would consider the bill shape of an inter-
generic hybrid to be unpredictable, as nothing is
known about the heritability of bill characters. As for
the rump patch, there is no assurance that any such
character would necessarily be inherited in a hybrid
and, in fact, in many Cape May Warblers in first basic
plumage the rump patch is not yellow, but a yellow-
green only slightly brighter than the back color.
In all plumages, Cape May Warblers have at least
a hint of a yellow or yellowish area just posterior to
the ear coverts (well illustrated in plate 6 of Curson
et al. 1994). This is presumably the area of the bird
to which Short and Robbins (1967) referred in stating
that the hybrid lacked "neck markings," but in fact
there is a distinct yellowish area at the sides of the
neck in the hybrid specimen, contrary to the state-
ment by Short and Robbins. I regard this as one of
the arguments in favor of the Dendroica parent having
been D. tigrina.
Other characters favoring D. tigrina over D. striata
are as follows. The upper tail coverts have vague but
obvious dark centers, positioned like the black feather
centers of D. tigrina, but absent or rare in D. striata.
The crown markings resemble those of D. tigrina; again,
these are rare in D. striata. The vague marks on the
back resemble the broader black marks of D. tigrina
rather than the linear (when present) back markings
of D. striata. The general somewhat orangeish color
of the bird seems more like an intermediate with the
bright yellow of D. tigrina rather than the definitely
greenish yellow of D. striata. Finally, Short and Rob-
bins (1967) themselves called attention to the resem-
blance of the hybrid to Cape May Warblers in breast
streaking, breast color, and spotting of the malar area
and sides of throat.
Short and Robbins (1967) included a long discus-
sion of white rectrix spots in wood-warblers, pointing
out that such spots are present in a small minority of
specimens of the genus Seiurus. As virtually all mem-
bers of Dendroica have such spots, it seems unneces-
sary to link the fact that the hybrid has small white
spots on the outer rectrices to the presence of these
in a few Northern Waterthrushes. The caption of their
figure 1, illustrating the patterns of the outer rectrices
of 12 species of parulid plus the hybrid, does not
specifically state that these were drawn from males
in first basic plumage. The tail spots in Dendroica are
variable in size and pattern, depending on both age
and sex (smallest in immature females) and also in-
dividually variable, as mentioned in connection with
Blackpoll Warblers by Short and Robbins (1967:540).
In examining specimens of Cape May Warblers taken
at random from the large series in Carnegie Museum
of Natural History, I found that definitively-plum-
aged males had significantly more white on their out-
er rectrices than shown in the example for this species
in the figure in Short and Robbins (1967). Males in
first basic plumage had less white, but in none was
the shape of the basal edge of the white spot as shown
in the figure. I judge the tail spots of the hybrid to
be irrelevant to a consideration of its parentage.
Short and Robbins (1967) pointed out that the
Blackpoll Warbler is widely sympatric with the
Northern Waterthrush, but the same is true of the
Cape May Warbler. I believe that the weight of the
evidence favors Dendroica tigrina rather than D. striata
as a parent of USNM 481595.
LITERATURE CITED
CURSON, J., D. QUINN, AIqD D. BEADIE. 1994. Warblers
of the Americas. Houghton Mifflin, Boston.
SHORT, L. L., JR., AND C. S. ROBBINS. 1967. An inter-
generic hybrid wood warbler (Seiurus x Den-
droica). Auk 84:534-543.
Received 7 November 1994, accepted 5 February 1995.