The White-crowned Sparrow [Zonotrichia leucophrys] is one of the sleekest looking sparrows. Like many sparrow species, it is understudied and has a number of subspecies that may be true species.
Because male White-crowned Sparrows learn the songs they grew up with and do not travel far from where they were raised, song dialects frequently form. Males on the edge of two dialects may be bilingual and able to sing both dialects. – Cornell Lab of Ornithology’s All About Birds