The number of baby gray whales born along the US Pacific Coast has rebounded from record low levels, suggesting that pregnant females are thriving despite a warming Arctic feeding environment.

The number of calves that passed Point Piedras Blancas near San Luis Obispo jumped from 945 last year to 1,018 calves in 2006, National Oceanic and Atmospheric Administration researchers have commented. Fewer than 300 of the 3-month-olds were spotted in 2000 and 2001. The whales have traditionally migrated to summer feeding grounds in the northern Bering Sea, but have been forced farther north in recent years because warming air and water has reduced the population of its favored prey, the fatty amphipod.

In 1999, about 270 whales washed up dead or dying on the Pacific Coast, some severely malnourished. But the whales appear to have taken advantage of melted polar sea ice, discovering new routes to food farther north near Barrow, Alaska, and finding enough crustaceans in the mud to nourish pregnant females, scientists say.

"It's a reasonable level of reproduction, and the overall trend over the past five years is positive," said Wayne Perryman, a NOAA fisheries biologist in La Jolla.