Pastoral poetry focuses on an idealized notion of the rural landscape. This tradition started with Hesiod and we can still find traces of it in the work of Wendell Berry and Dylan Thomas.
The Canadian Geese migration is one of those amazing feats of the natural world. When you think about this, and then watch them fly in their V formation, it makes sense that poets would incorporate them into their verse. Mary Oliver and Wendell Berry are two poets who took note of these birds and incorporated it into verse.