PIC: Robert Pattinson Nuzzles Kristen Stewart's Neck

Credit: Todd G/Splash News Online; Dimitrios Kambouris/WireImage.com

Kristen Stewart and Robert Pattinson usually refrain from PDA, but Thursday on the Montreal set of her new movie, a photographer caught them having a cozy moment.

During a break from shooting the 2011 Jack Kerouac adventure/drama On The Road, Pattinson, 24, nuzzled Stewart's neck.

Us Weekly recently reported that the two -- who will soon begin shooting the two-part Breaking Dawn -- have been living together most of the summer in L.A.

Don't expect them to talk about their romance.

Even when daytime diva Oprah Winfrey asked them in May if they were an item, Pattinson replied like he always does -- with a joke.

"Kristen's pregnant," he said. Stewart, 20, then added, "He really loves to shock people because he thinks it's funny. No, we've actually had this conversation. He's having the baby."