how aggressive do they get during mating season?

In my experience, females are only aggressive when incubating eggs, sometimes with goslings as well. Toulouse are much more docile geese than most, in general, so it shouldn't be that bad. A female won't suddenly get grumpy and aggressive when spring hits; it's only if she has babies that she might be, but then she might not if she's a gentle breed. The males may get aggressive during breeding season with or without goslings/eggs because they get quite significant hormonal changes and will be protective of their mates.

 

My female goose gets aggressive when I walked near her nest. She would "chase" me and try to bite my legs until I was far enough away. She would ignore me completely unless I got within ten feet or so of that nest. Now that she's broody she "fluffs" at me, but doesn't do much but protest a little when I pick her up and take her in the house (she's sitting on sterile eggs anyway). She's never attempted to bite me when I reach in there for her. But I've heard more stories of geese biting getting aggressive when they have a nest than not.

 

I have four adult females. Two of them, who are around two years old, have never been aggressive, even when sitting on their nests or even when I removed goslings from the nest. The other two do not get aggressive during the breeding season but they both get moody when sitting on the nest. I have to wear big tall rubber boots when they are sitting on nests in the spring when I have to get near them because they bite at my legs and feet. My toulouse is a gander and is a little over a year old. He has never offered to be aggressive up to this point but he is still young. My two year old gander wasn't aggressive either at that age but he sure is now and he's around 2 years old. He's rough stuff all year round now but particularly in the spring.