Birchard advanced with an 8-5 win over New Brunswick's Jessica Daigle on Wednesday that improved her record to 8-0.
"It's a great feeling, and hopefully we can keep winning tomorrow and get to that first spot," said Birchard, referring to the first-place bye to Sunday's championship final.
"It's definitely nice to get that rest and to not have to play that extra game. It's good to have the time off to relax because this week is very long and tiring."
The top three teams after the championship round robins conclude on Friday will qualify for the playoffs. The first-place teams in both genders will move into the final, while the second- and third-place teams will meet in the semifinals.
Birchard entered the Canadian juniors as one of the favourites after winning a silver medal at last year's championships in Napanee, Ont.
"I think there's always been confidence there. I think it's increased a little bit now that we've been doing so well in the round r,obin," she said. "Right now, I think we're feeling pretty good."
Meanwhile, two other teams — B.C.'s Corynn Brown and Ontario's Jamie Sinclair — clinched at least playoff tiebreaker berths with victories on Wednesday night to increase their records to 7-1.
B.C. defeated Nova Scotia's Mary Myketyn-Driscoll 8-2, while Ontario was an 8-7 victor over Saskatchewan's Jessica Hanson.
Yukon's Sarah Koltun is the only other team with a shot at the playoffs. She kept her hopes alive of reaching a tiebreaker with a 13-2 win over Quebec's Sarah Dumais to improve her record to 5-3.
In men's play, Nova Scotia's Stuart Thompson beat B.C.'s Tyler Klymchuk 6-4 and can clinch a berth to Saturday's final by winning its final two games.
"It's not fun for us as players to have nailbiters, but I guess the parents must like it," said Thompson. "It was nice to be up one coming home, but we needed to make a beauty. It couldn't have worked out better. It's unbelievable that we came away with a win from that one."
Nova Scotia improved to 7-1, and will play the only other 7-1 team, skipped by Alberta's Thomas Scoffin on Thursday before closing out against Ontario's Aaron Squires (6-2).
Alberta kept pace with a 7-4 win over Quebec's Felix Asselin. In the other championship round play, Manitoba's Matt Dunstone made a stunning quadruple takeout with his last rock of the game to score three and beat Ontario 8-6, and Saskatchewan's Brady Scharback turned back New Brunswick's Josh Barry 6-5.
The six teams in each gender that didn't qualify for the championship round are playing a seeding round robin to determine final rankings for next year's Canadian Juniors in Liverpool, N.S.
In men's seeding-pool play, Newfoundland and Labrador's Adam Boland beat Nunavut's David Kakuktinniq 17-0. In women's seeding games, Alberta's Karynn Flory toppled Carina McKay-Saturnino of the Northwest Territories 12-3 while Northern Ontario's Tirzah Keffer was a 17-1 winner over Nunavut's Sadie Pinksen.