Whether this is normal behavior totally depends on the swan species and more importantly the individual swan. Yes, swans can be extremely territorial and protective of their habitat, nests and young. With that said, some swans can go from Dr. Jekyll to Mr. Hyde when the testosterone levels increase during mating and nesting season. Some swans will be Mr. Hyde no matter what while others will only change during the mating season. Then, some swans will not care no matter who or what invades their territory.

The biggest issue is the amount of resources and the competition for those resources such as food, shelter from inclement weather and predators, adequate nesting sites, etc. If the swans feel like they are competing for resources, they just like geese or other wildlife will fight for those resources and remove the competition, even if it means that something is chased, severely injured or even killed. This is nature.

We don't want to insinuate that swans are the bad guys on the pond. If you take a goose in an area with very limited resources and ducks invade the goose's territory, the goose will react in the same way as the swan toward the ducks, think of a hiearchy as the larger animal will be at the top of the hiearchy and the smaller animal at the lower end. Each will fight and defend for their territorial rights with the smaller animal ususally being unsuccessful in the fight thus being chased, injured or killed.

All wildlife have been known to chase, severely injure and even kill competitors and their young. Usually, the young accidently get caught in between an adult fight and pay the price. This is probably what occurred in your instance. The young gosling left the protection of its parents and crossed into the swan's territory accidently and the larger adult bird grabbed the young bird or the young bird got caught in the middle of an adult fight and was easily caught.

Conversely, we have seen swans and their cygnets absolutely terrorized by geese. We have seen male Trumpeter Swans (40 lbs) tuck tail and swim so fast that they look like they are walking on water when fleeing in the opposite direction from geese So, again, it totally depends on the individual swan. We hope this helps. The Regal Swan