Point Reyes Bird Observatory, Observer 108
Eucalyptus specialists "down under"
are larger and better equipped than North American species to forage in
|By Rich Stallcup
||All drawings by Kieth Hansen. Copyright 1997.|
|Jeez! What a tree! It's late December in northern
California, but the list of birds foraging in the blossoms makes us feel
like we're in Manzanillo. In addition to many individuals of our regular
winterers - 20 Anna's Hummingbirds, 20 Audubons and 3 Orange-crowned warblers,
10 Ruby-crowned Kinglets, and a few starlings - there are two kinds of
orioles, a Palm and a Nashville warbler, a Warbling Vireo, and a Summer
Tanager! It's a Christmas Bird Count compiler's dream: six rare species,
all in one tree.
But... hmmm... something isn't natural here.
On the ground beneath the tree, we find a dead Ruby-crowned Kinglet, its facial feathers matted flat from black, tar-like pitch. Through a hand lens I can see that its nostrils are sealed shut. This little bird has suffocated as a result of its attraction to an exotic plant. I wonder out loud if the same fate becomes all the black-faced insectivores we see foraging in flowering eucalyptus. Years ago I found a dead hummingbird with black tar covering its bill and wondered why. It was in a cemetery in Oakland - under eucalyptus trees.
Several species of eucalyptus trees were imported to North America from
Down Under in the 1800s, for timber, windbreaks, and ornamentation. Eucalyptus
globulus, the blue gum, is native to Tasmania and has become the most common
large "euc" in California. During our winter (October to March),
many of them produce abundant flowers, which in turn attract insects that
invite these special sorts of birds. Without the presence of the trees,
many of these birds would migrate, as they should, into the American tropics.
They are what they eat
Birds have evolved body types, especially bill shapes and lengths, in
accordance with their environment, their feeding strategies, and the plants
in which they forage. Honeyeaters and other species of eucalyptus specialists
indigenous to Tasmania and Australia have long, curved bills: they can
probe the flowers without involving their feathers or nostrils. Leaf-gleaners
like North American kinglets, vireos, and wood warblers, have short straight
bills. To seek insects or nectar within eucalypus blossoms, they must insert
much of their heads, thus glopping up their faces. There are no native
North American plants that invite this type of harm.
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