Duo

THE Bullock's oriole and the equally beautiful Baltimore have been reclassified by the AOU (American Ornithologists' Union) and lumped together under the drab name of Northern orioles. I prefer to side with Thomas Howell, president of the AOU, who said, ''When I take my students at UCLA into the field and we see a Bullock's oriole, that's how I identify it.''

These orioles, particularly the Baltimore, are very special to me. One Baltimore, with its opulent colors of black and orange worn by Lord Baltimore, for whom this species was named, became a partner of mine, and I want to keep that name.

At the time, I was ''baby-sitting'' an aged woman, and my walk up the hill to her home passed a row of tall, sprawling elm trees on my grandfather's place. It made an excellent nesting spot for these birds, and several pendulous nests already hung from the very tips of the swaying tree branches, safe there from snakes, blue jays, or other predators.

One oriole had a rather individual way of singing. He would whistle two notes , the first a plain single note, the second following it with a bit of downward trill. I was delighted to discover I could imitate this. When he promptly whistled two more notes, one plain and the second even more trilled, I could whistle these also. From there I could not follow.

As I walked up in the morning and back again in the late afternoon, the bird would whistle those first-note series, which I would answer; then he would joyously sing the rest of his song alone. Soon, he was my escort in both directions. Reaching the end of the tall trees where our open lawns began, he would fly back. I, of course, was enchanted!

Then the blow fell. We were moving. It was less than what would be a city block away but too far to expect my Baltimore oriole to follow. We moved. I mourned.

Then, one early morning that next spring, I took a pan filled with corn out to the hens. On my way back I heard an oriole singing two notes. It paused. I held my breath - it couldn't be! Tremulously, I whistled the two distinctive notes. Immediately came back the next two, which I also whistled; then the oriole finished his song with a flourish.

Fortunately, I had already fed the hens, for I threw the now empty pan high in the air and hollered, ''Yippee!'' I guess my oriole was used to my exuberant ways, for he sang with me again before flitting back toward his home elm trees and nest-building.

He would be busy for a time now, and so were we as we readied the lower acres for a vegetable garden. The land was easy to harrow. Later, my small daughter, whose eye was as true as her singing voice, was on the tractor plowing arrow-straight rows across the garden.

Suddenly, from the top of the lone maple came a loud, mellow whistle. I promptly answered, and when the song was over I was surprised to see my Baltimore oriole flit above us across the open field to the tall tree beyond. He followed us often, back and forth, as we plowed and planted. For two seasons my oriole stayed near and we enjoyed our visits together.

Today, when the myrtle warblers migrate through Florida, I reluctantly say ''yellow-rumped warblers'' according to the AOU checklist, although I refuse to rename our Florida gallinules ''moorhens,'' but no one will ever hear me call the beautiful Bullock and Baltimore orioles by the pros ic name of Northern orioles.