The Song Sparrow is one of the most widespread and regionally variable birds in North America! It is also well known, and often a common bird in suburban areas, city parks etc. The variation in size and coloration is remarkable, from huge dark birds in the Aleutian Region of Alaska, to pale rusty colored birds in the Desert Southwest. Its distribution edges south to NW Mexico, and in particular down the Baja California Peninsula. However there are a series of subspecies found only on the Mexican Plateau, and these are entirely isolated from other Song Sparrow forms. These subspecies, zacapu, adusta, villai, and mexicana are large and have dark brown or black ventral markings, forming a necklace, and a clean, white throat. Recent molecular work suggests that the Sierra Madre Sparrow, currently in its own genus Xenospiza, is actually related to the Song Sparrow group. This makes some deal of sense based on visual similarities. Another open question is whether the isolated Mexican Song Sparrow populations are well differentiated either vocally or genetically from more northern birds. One thing about Song Sparrows is that in North America no matter how different they look, all are vocally clearly recognizable as Song Sparrows. This sparrow’s vocalizations are well studied. Each male has a repertoire of several songs. When a male is going head to head in an “heated territorial argument” the birds begin to match songs with each other, when singing at a low level of aggression adjacent males sing different song types.