Canada Geese goslings are often orphaned when they fall behind or something startles the parent geese and they take off.
The parent geese are good parents, but they can’t count so if they get to wherever they are going and are missing a gosling or two, they usually don’t notice. Luckily, geese families are very indiscriminate and will raise orphans. They have such a strong parenting instinct that when they hear a gosling cry, their instinct is to protect that gosling – whether or not it’s theirs.
Here at WRC we take advantage of the fact that geese can’t count. When a healthy Canada Goose gosling comes in, we find a goose family with goslings of the same size and introduce the orphan to them. Sometimes it can be difficult since the parents are trying to protect the goslings, but if we’re patient and give the parents time, they’ll adopt the orphan. Here’s a video showing the process.
Note that this does not work with mallards. They will actually attack ducklings trying to join their family that are not theirs.