It's no Jacuzzi, but a dirty bird's never choosey. And if you provide warm water in your birdbath on cold mornings, you'll turn it into the neighborhood hot tub. Who, you may ask, except for The Polar Bear Club, would go skinny-dipping on a snowy day? Well, how would you like to go all winter without a bath? Like all aviators, the cardinal must regularly clean and preen his flying machine. But how can he dry himself without a towel? Maybe freeze-dry?