Humpback whales return to the Stellwagen Bank Sanctuary from the Caribbean, including the Silver Bank Humpback Whale Sanctuary in the Dominican Republic. The humpbacks feed on the large numbers of sand lance that congregate on Stellwagen Bank.
Hammerhead sharks and spotted eagle rays continue to school at the Flower Garden Banks National Marine Sanctuary.
Larger numbers of humpback whales begin to leave the warm waters of the Hawaiian Island Humpback Whale Sanctuary for their summer feeding grounds in Alaska. Others may remain through June before making their long journey north.
Shorebird migration through Bowerman Basin NWR takes place in late April and early May; hawk migration begins at Cape Flattery; sea otter pupping through early spring, Olympic Coast Sanctuary.
Gray whales and calves pass through Cordell Bank Marine Sanctuary on their migration north.
Juvenile rockfish settle from the water column onto Cordell Bank throughout April and May.
During early spring, island wildflowers such as the Giant Coreopsis (Coreopsis gigantea) are in full bloom (March through early April).
Pacific harbor seal (Phoca vitulina) pupping season on San Miguel Island (February through May).
Gray whales (Eschrichtius robustus) migrate north through Channel Islands National Marine Sanctuary from calving grounds in Baja California, Mexico to Alaskan feeding grounds (Mid-February through May).
Peak egg-laying season for California brown pelicans (Pelecanus occidentalis californicus) on Anacapa and Santa Barbara Islands (March and April).
Brant geese (Branta bernicla) stop to rest and feed in the Channel Islands region on their annual migration between Mexico and Alaska (March through May).
Xantus's murrelets (Synthiboramphus hypoleucus) breed and nest on the Channel Islands (March through July).
Double-Crested cormorants (Phalacrocorax auritus) begin nesting on the Channel Islands.
Red-Necked phalaropes (Phalaropus lobatus) can be seen in the Santa Barbara Channel in the spring (April and May) and fall (August through October).
Peak spawning season for Grunion (Leuresthes tenuis) on southern California beaches. Grunion leave the water at night to spawn on the beach in the spring and summer months two to six nights after the full and new moons. Spawning begins after high tide and continues for several hours (late March through early June).
Island Fox (Urocyon littoralis) pups are born in early spring on the Channel Islands (March and April).