Researchers confirmed the birth the next day, dispatching a team from San Juan Island that encountered in the early morning as they exited Admiralty Inlet with the new baby.
The video, shot Thursday near Vachon Island in Washington state, shows the calf swimming next to the killer whale known as L77, who had previously been pregnant. He estimated the calf is several weeks old.
About 40 percent of newborn calves do not survive their first few years, Balcomb said.
Last summer, a calf born to the whale known as J35 died shortly after birth, and its mother carried the corpse around on her nose for 17 days, drawing global attention.
Scientists with the Center for Whale Research confirmed to Q13 News an orca calf was spotted alongside L77, its mother.
"We're trying to let the joy in and have the hope that this one will make it", Berta said.
WATCH: Footage from KING 5 shows a new calf swimming with the Southern Resident killer whales. The lifetime buildup of toxics is mostly offloaded into their firstborns.
Here is the baby picture with L124, the youngest living SRKW friskily following L25, the oldest living SRKW.
Balcomb said the newest youngster looks healthy.
ABOUT THIS SERIES In the weeks and months ahead, The Seattle Times' "Hostile Waters" series will continue to explore and expose the plight of the southern resident killer whales, among the most-enduring symbols of our region and most-endangered animals.
The biggest threat facing the orcas, scientists say, is declining stocks of chinook salmon.
The orca calf will be designated L124, signalling its connection to the L pod of southern resident killer whales, a clan comprised of three pods: J, K, and L. She continued her so-called "tour of grief" for 17 days.
Last month Washington Gov. Jay Inslee announced plans to help the population recover - including $1.1 billion in spending and a partial whale-watching ban.
The status of those pregnancies remains unknown.