At top speed, a needle-like bird beak, flared with chestnut
and horns of gold and followed by bright black-and-yellow tiger stripes,
hurtles towards its target. This is the view that many birds have of
the beautiful but aggressive male Cape May Warbler as it chases all
comers from a favorite tree. Birders usually gain a very different
view of this bird. Patient observers are well rewarded when they
glimpse a Cape May giving its simple sibilant song from the top
of tall tree
The Cape May Warbler is so named because it was first collected
at that world famous New Jersey migration site in 1811. However,
the species is most characteristic of the northern boreal forest,
from Maine to the Northwest Territories, in the summer and the woods,
gardens and plantations of the West Indies during the winter months.
It is better described by its Latin name tigrina reflecting the tiger
striped appearance of the adult male. The adult male retains this
plumage throughout the year, but the facial colors are partly obscured
by green feather edgings that wear as spring approaches. Females and
young are often dull olive brown and streaked with only a pale yellow
rump and a hint of the yellow neck patches to remind us they are indeed
Cape May Warblers.
During the brief summer breeding season, Cape May warblers are
patchily distributed in forest of spruce, fir or jack pine conifers
becoming particularly common at outbreaks of the spruce budworm. The
late Robert MacArthur, a pioneer of warbler ecology, demonstrated that
this species (along with a few others) increases its clutch size when
breeding during these outbreaks. When defending territories at these
outbreaks, male Cape May Warblers can be quite aggressive chasing larger
warblers, such as Yellow-rumped and Bay-breasted.
Cape May Warblers commonly feed on nectar or fruit during the
non-breeding season. Because of this dietary preference, they are
commonly found in gardens or shade coffee plantations, where flowering
plants are abundant. Cape May Warbler's have strikingly narrow bills for
inserting into flower corollas, or puncturing the sides of flowers to rob
nectar. In addition, it is reported that Cape May Warblers have
semi-tubular tongues which increases the efficiency of the uptake of
nectar through capillary action. This aggressive species is well known
for defending certain flowering plants from all other small birds. One
study reported that Cape May Warblers defended flowering mesquite from
other birds, mainly Northern Parulas, through long-distance chases every
10 or so minutes.
Data from the North American Breeding Bird Survey indicate that Cape
May Warblers have been declining since the late 1970s. Similar declines
have been reported for banding stations as well. The most likely
explanation is that the population is responding to declining numbers of
spruce budworms in eastern Canada (although outbreaks continue in western
Canada). Since budworm populations are cyclical, we can expect Cape May
Warbler numbers to increase in coming years. However, Cape May Warblers
prefer areas of boreal forest with tall timber. As logging continues full
force throughout the boreal forest, the loss of mature forest may
contribute to long-term declines. Additionally, Cape May Warblers are
particularly common in shade coffee plantations on the wintering grounds.
As these plantations are converted to shadeless plantations, winter
habitat may be lost as well.