Gray whales are now found only in the North Pacific along the west coast of North America and along the coast of eastern Asia. Each fall, the North American whales migrate south to Baja California, in Mexico, most of them starting in November or December. They winter mainly along the west coast of Baja California, where calves are born in lagoons and bays from early January to mid-February. The northbound migration generally begins in mid-February and continues through May, with cows and newborn calves migrating northward primarily between March and June. Most of the North American whales spend the summer feeding in the northern Bering and Chukchi Seas. However, some are observed in the summer, feeding in waters off of Southeast Alaska, British Columbia, Washington, Oregon, and California. Photo-identification studies of this "Pacific coast feeding aggregation" indicate that they move widely within and between areas on the Pacific coast, are not always observed in the same area each year, and may have several year gaps between resightings. Newborn gray whale calves are about 5 m in length and as adults can grow up to 14.1 m and can weigh over 35 tons.