Adapted from Jim Conrad's online book A Birding Trip through Mexico, This excerpt from "Above Xoconostle" in San Luis Potosí state

Arriving in Xoconostle on a Sunday morning an hour after dawn, frost still whitens a few grassblades and loose chicken feathers on the ground. As the bus pulls away and I strap on the backpack, diminutive María López, an old woman keeping warm with a red shawl wrapped over her head and across most of her face in Moslem style, stands not far away looking at me. She operates a tiny roadside hole-in-the-wall selling softdrinks and crackers. From her I buy a couple of days' worth of carbohydrates.

María cannot suppress her questions. At my mention of birds her dark eyes peeping through the slit in the red shawl flush with pleasure. She asks me to follow her into the tiny courtyard behind her shack.

Two small, wire birdcages hang on the unfinished boards constituting her house's walls. One cage holds three birds, the other four. On the cages' floors are split-open pricklypear fruits, xoconostles, their pulpy flesh scarlet and glistening. Also there's alpiste -- freshly cut clusters of pods of a turniplike plant, the pods gorged with B-B-size seeds, and sold in Mexican markets as the preferred food for caged birds. María tells me each bird's name and history, says that such birds are very common in the desert around Xoconostle, that they sing beautifully, and then she asks me by what name such birds are called in English.

I am confused. Instantly my credibility as a gringo bird-specialist flies out the window.

From the short, thick bill it's easy to see that this is a kind of finch, but the males are pale orange, and I can't recall having ever seen anything orange in Mexico. I explain my astonishment, and bring out my bird book to show María that it must be closely related to strawberry-red House Finches, which I know very well, but these orange birds...

María laughs like a child and says that of course everybody knows that before these birds are caught they are then strawberry red. It's just that once they're caged up, they turn orange, and nobody knows why.

I take leave of María and begin hiking upward and eastward. The low, sparse, mostly spiny, cactus-rich vegetation along the road is indeed home to innumerable strawberry-red, male House Finches who sing their pretty, twittering melodies even on this cold morning in late October. It's sad to think about these birds fading once they're taken from the wild. However, it's hard to be angry with María for caging them.

She takes the best care of them she can, even feeding them xoconostles, which I know the birds love. I know this because Sahagún, the Spanish priest who during the 1500's wrote the history of the Aztecs, relates that the Aztecs also kept House Finches in cages, calling them by the name of nochtótotl, which meant "birds of the cactus fruits."