Bullock’s Orioles have a black throat
and a narrow black line through the eye. Notice that this
species has only one large white wingbar.
Wikimedia Commons photo
It is said that
“Whatever happened to the Northern Oriole?”
the lady asked me. “It is right here on page 304 of my bird
book, but I can’t find it in your bird guide.” I asked in what
year was her guide published. Looking in the front of the book,
she replied “1983.”
“Ah, that explains it” I said. “My book
was published in 1999. The Northern Oriole only existed from
1983 to 1998.”
Of course, that doesn’t really explain how
a bird can come and go in the bird books, does it? No, the
Northern Oriole didn’t become extinct. It was the victim of
Splitters are ornithologists who find
evidence that a particular species of bird should rightfully be
split into two separate species. That was what happened to the
Northern Oriole in 1998. It was split into the Baltimore Oriole
and the Bullock’s Oriole. The other name was officially
Baltimore Orioles breed in the open,
deciduous woodlands common to the northeast. They arrive on
their breeding grounds around the 10th of May and immediately
start to sing their lovely whistled song. Soon, they begin to
build remarkable hanging, pouch-like nests. Usually the female
alone makes the nest which she does by pushing plant fibers
through a network of woven strands. Her slender pointed beak
goes through rather like a sewing machine making a stitch. When
she pulls her beak back out she grabs a different fiber, thus
interlocking the strands. Over and over she does this.
Finally, when the nest resembles an elongated wad, she gets in
and pushes and shoves until a pocket is formed. Although well
hidden in large trees like American elms, the durable nests can
be seen when the trees have lost their leaves in the fall.
The Baltimore Oriole's head is completely
black and he has two wingbars. The front bar is orange and the
back one is narrow and white.
Wikimedia Commons photo.
Bullock’s Orioles, on the other hand, live
in much more arid environments. They are common breeders in the
western half of the U.S., including South Texas. Bullock’s
Orioles seek out mature mesquites for their nest sites. And in
Bee County they often choose mature live oaks. Their rather
unmusical song sounds something like “Chop, chop, chop.
Eee-ee-bird.” The male Bullock’s helps the female build the
nest. In one account, the male was on the outside of the
developing pouch and the female on the inside. He would poke
his bill through the wall and hand a fiber to the female who
would in turn push it back through in a different location. The
result was a rather beautiful, smoothly-woven, pendant nest.
It seems like these two orioles were
different enough to be two species, doesn’t it? They don’t look
much alike. So, what had happened in 1983 to have combined
them into the new species, the Northern Oriole?
Evidence had been accumulating for years
that where the two orioles had an overlap in range, i.e. where
east meets west, they would interbreed and successfully raise
hybrid young. This suggested that the two species were not true
species, but simply races of the same species. The “lumpers”,
another camp of ornithologists, argued that the two orioles
should be lumped together as a single species. The Northern
Oriole was born!
Perhaps because of this lumping,
birdwatchers began to really take good looks at the Northern
Oriole and its two subspecies. Scientists did further
research. Geneticists studied their DNA. Field biologists
noted that yes, the two subspecies did interbreed in a few
localities in Oklahoma and Kansas, but this hybridization was
not widespread. Plus, Baltimore and Bullock’s Orioles are
really very different in plumage, song, and habitat. The
hybridization came to be viewed more as a fluke. The
reproductive isolating mechanisms (behaviors, songs, and choice
of habitat that kept the two orioles from interbreeding) were
breaking down in only a few rare instances.
The final piece of evidence came in 1995.
A study of the DNA of the whole blackbird family showed that
Bullock’s and Baltimore Orioles were not closely related after
all! The splitters convinced the members of the American
Ornithologists’ Union to officially divide the Northern Oriole
back into two individual species. When The A. O. U. Check-list
of North American Birds, seventh edition, came out in 1998 we
again had Baltimore Orioles and Bullock’s Orioles.
Did you notice that I said blackbird
family? Yes, orioles are really blackbirds that happen to have
colors other than black in their plumages. If you could dress a
plain blackbird, or a grackle, in a tiny orange muscle shirt, he
would resemble an oriole!
Like blackbirds, orioles do sometimes
sample fruit. This can get them on the wrong side of a farmer
or orchard manager. But studies show that only 21% of the diet
is vegetable matter. The rest is insects, and a lot of the
insects consumed are true pests. The orioles feast on webworms,
grasshoppers, boll-weevils, and stink-bugs, to name a few. As
one writer puts it “only a short-sighted churl or ignorant fool
would begrudge (an oriole) the few green peas or berries it may
help itself to while in season. It fully earns all it takes… by
the immense amount of good it does in the destruction of noxious
The orioles’ penchant for fruit has given
birdwatchers the idea of feeding them. You can mount half an
orange on a platform, or use a nectar feeder. The nectar is the
same as hummingbird juice (one part sugar to four parts water),
but the holes in the feeder are larger to accommodate the larger
bills of orioles. It is fun to watch the Bullock’s Orioles sip
nectar and realize that for 15 years they were only a
The eighth edition of the A.O.U. Check-list
is due out in 2013. I wonder what surprises the lumpers and
splitters will have for us this time?