I had never known this was a thing either. I always see the geese on the ground.

I did a little more digging and it is unusual for geese to nest in trees, it’s not rare. They either like tree cavities or existing raptor nests. Nobody seems to really like the geese doing this. This owl is very not happy, and also I can upon a few people that tried to set up nests for more in danger birds like osprey, only to have some overly plentiful goose come and steal the spot.

Found another little photo series on Flickr showing another great views of a CG/GHO fight. Here’s the best one for anyone that doesnt want to follow the link.

It doesn’t sound like they will eat the chicks, just “evict” them.