318 
ness on the basal parts of the feathers on the sides of the neck just behind the ears. This 
slight tinge sometimes shows in life when the bird turns its head, but with the bird in the 
hand the feathers must be separated to show it. 
Field Mark s. Adults and juvenile males are distinctive. Juvenile females may be 
recognized by the peculiar, fine, dim striping of breast against a slightly buffy, light olive- 
grey ground or by the concealed yellow spot on sides of the neck as described above. 
Nesting. On low branches in small trees in pastures or woodlands in partly pensile 
nest of twigs and grasses fastened together with spider-web and lined with horsehair. 
Distribution. Eastern North America. In Canada, west regularly to Manitoba, 
occasionally to central Saskatchewan. Has been taken as far north as Mackenzie valley. 
652. Yellow Warbler, summer yellow-bird. Dendroica aestiva. L, 5-10. Plate 
LXIX A. Male: bright yellow, greening slightly on back, with fine rufous stripes across 
breast and along flanks. Females and juveniles are similar but duller and without breast 
stripes, and in some specimens almost more generally green than yellow. 
Distinctions. Practically the only all-yellow Warbler. Some specimens of Orange- 
crowned, Nashville, Wilson’s, or other Warblers may approach occasional Yellow Warblers 
in colour, but none of them have the inner webs of the tail feathers distinctly yellow as 
has this species. 
Field Marks. The even and uniform bright yellow of spring birds is unmistakable- 
Some females are more green than yellow, but the green-edged wings and yellow tail, lack 
of colour contrasts, size, and actions of the bird are easily recognized. 
Nesting. In an upright crotch n bushes and small trees in nest of fine fibres and a 
large amount of plant down, lined with plant down and sometimes long hairs. 
The Yellow Warbler is one of the few species that sometimes refuses to incubate 
Cowbirds eggs. Instead of throwing out the intruding egg, however, it builds a new 
nest over the old one, burying it and its entire contents, including often some of its own 
eggs, in the foundation of the new structure, in which another set of eggs is deposited. 
Distribution. North and South America. In Canada, across the Dominion north 
to the limit of trees. 
SUBSPECIES. Two races are recognized in Canada. The Eastern Yellow Warbler 
Dendroica aestiva aestiva west to the Pacific slope. On the west coast the Alaska Yellow 
Warbler Dendroica aestiva rubiginosa is the accredited form. It is slightly more olive 
on the back and the breast stripes may be slightly fewer and less decided, but the distinctions 
are so fine that it is difficult to delimit the ranges of the two. 
This is the commonest breeding Warbler in southern Canada. It 
shares with the Goldfinch the popular name of Wild Canary, but the lack 
of black anywhere will determine it at a glance. It is found in shrubby 
localities in open country or along stream or marsh edges. It is a common 
visitor to the garden and its cheery little song is very pleasing. In the 
autumn the Yellow Warbler is one of the first species to leave. 
654. Black- throated Blue Warbler. Dendroica caerulescens. L, 5-28. Male: 
deep blue above from crown to tail-coverts; below, white; cheeks, throat, foreneck, and 
flanks black (Figure 288). Female dull, dark, ohve 
all above, lightening on throat, breast, and abdomen 
to dull olivaceous-cream. White spot at base of 
primaries in all plumages. 
Distinctions. The male, so descriptively named 
and strongly marked, is very distinctive. The female, 
however, especially in autumn, is more difficult to 
distinguish; it may resemble either the juvenile of the 
Tennessee, the autumn Black-poll, or the Bay-breast. 
The streaked back and wing-bars, however, of the two 
last are absent. It is darker and more greyish green 
than the Tennessee above and more buffy below. An 
indistinct and partly concealed white or light spot at 
the base of the primaries is always diagnostic of 
females of this species. 
Field Marks. The male is distinctive. The 
female in any plumage can usually be recognized 
from all other evenly coloured dull green Warblers by the sometimes very faint light spot at 
the base of the primaries, which shows more conspicuously in life than might be expected. 
Figure 288 
Black-throated Blue Warbler (male); 
natural size. 
