Some info from canadagoose.org: Canada geese (and swans) mate for life. Mated pairs not only raise and protect their young together, but also look out for one another over the course of their lives. One mate will stay by the other's side if injured or dying, even if the rest of the flock is moving on. They are extremely devoted to one another.
And further description of the mating / courtship adapted from preservewildlife.org. These steps can be seen in the photo story below (although I've added a few captions on the photos too - hover over or click to expand and read):
During mating season, couples will go off together and be alone. ... The displays that the males perform range from the Head-Up-Tail-Up (male throws his head back and jerks with his tail feathers erect) to the Grunt (male rears out of the water and slowly sinks back down while making a loud grunting sound). Both the male and accepting female then continues the courtship by performing other displays separately or in unison. Mating occurs in the spring on the water and at night time (that’s why they aren’t seen mating).
Copulation begins with both sexes bobbing their heads up and down and touching their bills to the water horizontally with their necks extended. As the female extends her neck and her wings flattened out, the male “joins” her (while in the water). The female is usually partially submerged or completed submerged (with only head out of water) while copulation takes place. The male stands on her back. After copulation the female bathes while the male faces her and then he bathes.
Technical details: Sony a850 with Sigma 50-500mm (Bigma) lens.