Geese on the move

Geese, probably Canada geese, on their way northward. 

One of the really thrilling sounds of the season is that of geese on the move.While working out in the garden the other day, I heard them off in the distance. They flew over me before I actually spotted them - lots of them., way up there. There are about ninety geese in this chevron. This photograph was made on February 29, 2016.

Geese

I don't have an image or a sound recording for this, but one of the big excitements of the season is taking place daily now: when I walk Biscuit in the morning we see and hear formations of geese heading north. This is a moving, even thrilling, thing to experience.  I used the pronoun "we" deliberately in that first sentence: Biscuit will look up into the sky and watch as the geese pass. The group we saw this morning easily numbered over one hundred geese.

I've always assumed that these birds respond to the changing day length rather than to temperature: is that true?