Biologists are concerned about a North Atlantic right whale and its 3-week-old calf seen swimming in the waters of Cape Cod Bay. Specialists said it is highly unusual to see the endangered whales off the coast of Massachusetts at this time of year. Charles ‘‘Stormy’’ Mayo of the Provincetown Center for Coastal Studies said he is worried about their ability to survive colder waters. The mother and calf were first sighted Jan. 12. Typically, right whales give birth in warmer waters off Georgia and Florida and arrive in Cape Cod Bay with their young in the spring.