There's a baby boom going on among a clan of the world's most endangered killer whales.

Whale watchers off the British Columbia coast have sighted a fourth calf born since December to the group of Southern Resident Killer Whales that also frequent Washington State waters.

Naturalist Jeanne Hyde first spotted the latest addition while aboard a whale watching cruise. At first, she thought it was another orca born earlier in the year. Then she saw the dorsal fins of both calves break the surface at the same time.

The birth of ‘J52', as the newest arrival is called, increases the estimated number of wild mammals in the community of Southern Resident Killer Whales by three percent, to a total of 81.

It's been almost three years for the clan since a calf has survived to its first birthday, according to the Center for Whale Research. The survival rate is normally about 50 percent for any young orca. The latest string of births have allowed for cautious optimism, however, and even a bit of excitement.

The research community and whale watchers in the Pacific Northwest are keeping their collective fingers crossed that the endangered community has "finally turned the corner."

Photo Credit: Jeanne Hyde courtesy of Center for Whale Research (shows both calves' dorsal fins breaking the surface)