THE VERMILION PARROT by David Rains Wallace (Sierra Club Books: $18; 224 pp.). If, without resorting to stimulants, you can buy the idea of a 5-foot-tall English-speaking parrot crashing around in the wilds of Mexico with a naturalist and a female spy, you are halfway home. Wallace's second "eco-thriller" ("The Turquoise Dragon" was the first) gives new meaning to the phrase off the wall. Why is the National Aeronautics and Space Administration trying to cover up the loss of a load of human-sized parrots (actually, hybrid 70-million-year-old dinosaurs that it found in space)? Who is trying to smuggle giant condors into Mexico? What foreign government does the mysterious Jill represent? Wallace has some pithy things to say about the environment, but it's unclear what message the reader is meant to get about this noisy, overbearing, 5-foot parrot-dinosaur and her just-hatched babies.