Beginning each spring and continuing until the temperatures really start to climb in the summer, thousands of bats migrate to the so-called "Phoenix Bat Cave" near the Arizona Biltmore. The "cave" is actually a Maricopa County Flood Control ditch, but it has the proper temperatures and protection for these tiny flying creatures. During bat season, visitors to the cave (which is marked by a plaque from the Arizona Department of Game & Fish) can see dozens of bats flying out at dusk, hunting insects. There are two types of bats who make their home here: the western pipistrelle, which is the smaller of the two groups and the first to fly out of the cave in the evenings in fluttery flight patterns, and the Mexican free-tailed bat, which is a female colony that comes to the cave to birth and raise their young (the highest number are believed to be in the cave in July and August). Accessing the cave requires parking near 40th Street and Camelback, then walking along the north side of the Arizona Canal for about half a mile. The entrance to the cave is behind Phoenix Country Day School, north of the canal.