Cerulean Warbler
Cerulean Warbler is one of the great gems in the family Parulidae. It
breeds in eastern hardwood forest and is quite local and rare in its
habitat requirements. It winters in the Andes of Colombia and is at
risk at both ends of its range. Along with Golden-winged Warbler, this
species has shown serious declines and is one of the warblers with the
greatest conservation concern.
Ceruleans have a fascinating migration, crossing the Gulf in
spring making landfall mostly in the eastern Gulf in mid-April. Most
seem not to make landfall on the coast at all, and the above animation
shows that they just "magically" appear on the breeding grounds.
Increasingly it is thought that warblers like Cerulean may do more of
their migration in non-stop hops, jumping directly from Central America
to breeding grounds in the Appalachians. For birders on the Gulf Coast,
spotting a Cerulean is a real treat, and that fact along with the
animation above give some support to the theory of a longer non-stop
flight. Watch the fall migration in this species--they just fade away.
Ceruleans are early migrants, rarely seen in September, and are among
the toughest fall migrants to detect. It may be that their departure is
in another non-stop flight and with the birds being silent on southward
passage, the STEM map doesn't even show the extremely low probability
of finding one in fall migration.
This is not one of the very best animations and anyone familiar
with the distribution of the species will spot some problems. The
summer distribution shows lows of "bleed" on Coastal Plain areas where
they don't occur. They essentially never occur in northern
Maine. As is usually the case with STEM results that are of lower
quality, the species has a very low predicted occurrence rate of 0.002
to 0.006. An ongoing research topic will be to learn how to improve
these models for rarer species. Will increased data volume solve the
issue for us? Must we have more eBird surveys in northern Maine to
"prove" to the models that Ceruleans do not occur there? As future
iterations of these maps become available, we hope to answer those
issues and provide even more accurate maps.
