A land manager's guide to conserving habitat for forest birds in ...

Cerulean Warbler Dendroica cerulea
Female Cerulean Warbler —
Photo: Greg Lavaty
Identification
(11.5 centimetres)
The Cerulean Warbler
breeds in mature, deciduous
forests in association with
tall, large diameter trees.
Males are sky blue above
and white below with a thin
blue-black necklace and
dark streaked sides. Females
are drab blue-green above,
whitish below with a pale
yellowish eyebrow. Both
sexes have two prominent
white wing bars and white
tail spots.
Conservation Status
This area-sensitive species is
of great conservation concern
because of its small range and
population size. It has
declined an alarming
70 percent throughout its
range since 1966 (four
percent per year), due to loss
and fragmentation of mature
forest habitat, and loss of
appropriate vegetation
structure and composition. The Cerulean Warbler is listed as a
species of Special Concern in Canada and the United States.
Breeding Biology
The Cerulean Warbler’s breeding range extends from the centraleast
United States north to southern Ontario and extreme
southern Quebec. It has a very patchy distribution within this
range, breeding in uplands or wet bottomlands in mature or oldgrowth
deciduous forest. Ceruleans have specific preferences for
large, tall trees, open understorey, and a structurally diverse
canopy with multiple vegetation layers. They typically build
shallow woven cup nests, far out on a horizontal branch in the
upper canopy. Females lay four grayish, greenish, or creamywhite
eggs that are spotted or blotched with reddish and greyish
brown. Only one brood is raised per season.
Diet
The Cerulean Warbler is insectivorous, typically foraging high in
the canopy, hopping along small branches gleaning insects from
leaves and twigs. Its diet is comprised mainly of caterpillars,
spiders, bees, wasps, and weevils.
Management Guidelines
The Cerulean Warbler has become a symbol of healthy, mature
deciduous forests. It is rather intolerant of intensive habitat
disturbances, but does breed successfully in sites managed for
maple syrup, and will tolerate selection and shelterwood harvests.
Ceruleans benefit from the protection of old-growth or wilderness
areas and management efforts that focus on the production of high
quality timber, because they rely on tall, large diameter, full canopy
trees. These practices allow for longer rotations, uneven-aged
structure, vertical diversity, and tall canopies, while high-grading,
diameter-limit cuts and even-aged systems that remove most or all
the largest trees are unsuitable. Carefully applied group selection
cuts may be a good tool, since Ceruleans not only associate with
small canopy gaps and internal openings, they select for midtolerant
trees like oak and hickory.
How to Find
Slap on your hiking boots and grab a good pair of binoculars if
you want to find this tiny forest interior bird that spends most of
its time in the
canopy of mature
stands. Listen for
its distinctive
rapid highpitched
buzzy
“zee zee zee
zizizizi eeet” song
that rises
at the end.
Did you know?
Male Cerulean Warbler feeding nestlings —
Photo: L. Walkinshaw/VIREO
• The Cerulean Warbler migrates farther and sooner than other
warbler species, arriving at breeding grounds up to two weeks
earlier and returning to wintering grounds as early as August.
• Over 60 percent of Cerulean wintering habitat in the South
American Andes has been converted to crop land largely for sungrown
coffee and coca.
• The female Cerulean Warbler is known to drop vertically from the
side of the nest with wings closed, only opening them when she
is several metres below the nest, a behaviour known as bungeedropping.
• When renesting after a failed nest, females often uses spider
web from the old nest to start construction on the new nest.
Fresh lining is gathered for the new nest, but spider web may be
too valuable and time-consuming to waste.
Bird Species Accounts 125