(Dendroica coronata). The distinctive note of Mourning Warbler, by com¬ 
parison, is a sharp "spic", remarkably similar to the chip note of the 
Indigo Bunting (Passerina cyanea). Some field guides (Dunn and Garrett 
1997) describe the call note of Mourning Warbler as "flat To our ear it 
is the note of MacGillivray's that is flat, with Mourning being sharp. In 
any event, Mourning sounds like an Indigo Bunting, Macgillivray's like 
a yellowthroat or hoarse Yellow-rumped Warbler. These differences in 
voice are consistent, and in our opinion, diagnostic. 
The throat and upper chest area (the area enclosed by the hood) on our 
bird were grayish white, without any hint of yellow, and diffusely 
streaked with dusky but not black. Finally, the eye crescents on the Staten 
Island bird were bold, white, and together encircled about 2/3 of the cir¬ 
cumference of the eye. Mourning Warblers, by contrast, have much nar¬ 
rower, off-white eye-rings that tend to encircle a larger proportion of the 
circumference of the eye. 
IDENTIFICATION AND AGING 
To check the validity of field characters cited by various authors as 
diagnostic in separating MacGillivray's from Mourning Warblers, we 
examined specimens in the AMNH. We selected 50 specimens of 
MacGillivray's Warblers and 39 specimens of Mourning Warblers col¬ 
lected between 15 Aug and 31 Jan. We omitted adult males from our 
selection, using the reasoning that our bird could not have been an adult 
male on the basis of plumage characters. Adult males in fall and winter 
are similar to adult males in spring and summer (Dunn and Garrett 
1997). We measured the wing chord and tail length of all specimens, in 
order to use the difference in length of these two structures as a basis for 
assigning each specimen to one or another species (Lanyon and Bull 
1967; Pyle 1998). Then we assessed, for each specimen that could be 
unambiguously assigned to one or the other species on the basis of mea¬ 
surements, whether the distinctiveness of the above mentioned field 
characters held true. 
For MacGillivray's Warblers, we found that three out of fifty speci¬ 
mens had some yellow on the throat, but none of these three had as 
bright or extensive yellow as did the average Mourning Warbler. Twenty 
of the 39 Mourning Warblers that we examined had wing-minus-tail 
measurements within the range of overlap between the two species, and 
seven of the twenty had wing-minus-tail measurements well outside the 
range of Mourning (wing-minus-tail of less than 5 mm) and within the 
The Kingbird 2000 March; 50(1) 
4 
