A girl and boy piglet prove they are swine for all seasons as they savor the best that each of the 12 months has to offer. "Sing of a song of skiing,/ skiing in the snow./ Wax your skis/ and bend your knees/ and down the hill we go," writes Bunting (Smoky Night) for January, as McCully (Mirette on the High Wire) sends the bundled-up duo schussing through a crisp alpine landscape. In April, the pigs plant seeds ("Sing a song of gardening"); in July, they expertly hang 10 ("Sing a song of surfing") on a giant, cresting wave; and in November, they stuff themselves silly with a vegetarian repast of "Hash and mash,/ potato smash." Bunting's rhymes should fall gently on younger ears ("Pull the weeds/ and plant the seeds/ and watch the flowers grow"), and her writing picks up verve during the pigs' more energetic activities. McCully's watercolors are the real treat, however, especially those devoted to warmer months (never mind that she shows vegetables instead of flowers in that garden). Layers of delicate color capture sunlight dappling an emerald lawn, and the way a panoply of greens and blues seems to shimmer on the surface of a lake. Cheery, full-spread pictures alternate with beguiling sequences of vignettes, creating a perky visual rhythm not suggested by the relatively mild jacket art. Ages 3-6. (Sept.)