If you are looking for birds that are good at swimming and fishing, then your answer is here "The Cormorants". Some refer to them as the ecosystem destroyer but they also signal that an ecosystem is doing well. From their Pose on trees, to their ability to swim and catch fishes both big and small just to satisfy their greed, Cormorants are just one type of bird that people have a lot to say about and no matter you or anyone else have to say, the bird is readily available almost everywhere on the planet.
This bird is a member of a family of 40 fish-eating species known as Phalacrocoracidae with a few members being Poikilocarbo, Urile, Microcarbo, phalacrocorax, Gulosus, and Nannopterum just to mention a few. So they are not the the only fish-eating bird so people should give them a break. These birds live in coastal regions since that is where they can have access to food easily so they can dive into the water and get a good tasty meal. If I were the one, I would build my home close to my food as well; (Rule 1 of survival).
This bird can go as deep as 40 meters in search for food but it isn't like the dive to search for it, they actually dive to go get their food because they search for their food either by looking from a tree or by swimming like a duck and when they see a prey, they dive very deep into the ocean for their delicious meal. Similar to Scuba divers, this bird have webbed feet which allows them to propel under water like they have fins.
Unlike many fish hunting birds, their feather or plumage isn't waxed or resistant to water, in fact this bird likes its feather getting wet so it can be able to dive very deep since it sinks easily. The bird then uses its beak to hold its fish till it reaches the top of the water after which it reaches for a tree or surface to dry its feathers.
These birds have different species and so they are found almost everywhere including Antarctica, and depending on whom you ask, they can be seen as a blessing or as a curse. Because this birds live in thousands of number at a time, their feeding on fish destroys the fish ecosystem and they can lead to the loss of numerous fishes, this isn't all, their perching on trees usually destroy tree canopies as a result of their population and nesting practices, also their feces also causes harm to vegetation as a result of its acidity.
For the fishing part of cormorants, this is still very debatable because they are not the only species that are competing for food in the water, other organisms including human also compete for food in the ocean so this can be debated over time but when it comes to their effect on trees and the soil, this is for sure real. Their nesting activities kill tree canopies as a result of their excretion covering the tree and preventing the tree from performing photosynthesis.
Their feces rain down a lot when they are nesting and this covers the leaves of the tree which prevents them from being able to photosynthesize as they ought to. Also, their nests are very big and heavy which overtime posses a lot of weight on the tree causing its branches to break. Also when their feces touches the ground and changes the soil chemistry thereby reducing the amount of nutrient the soil can absorb.
READ MORE
https://www.allaboutbirds.org/guide/Double-crested_Cormorant/overview
https://www.bto.org/understanding-birds/birdfacts/cormorant
https://ebird.org/species/grecor
https://www.rspb.org.uk/birds-and-wildlife/cormorant
https://icwdm.org/species/birds/cormorants/cormorant-biology/
https://icwdm.org/species/birds/cormorants/
https://www.researchgate.net/publication/270105065_Biology
https://link.springer.com/article/10.1007/s10021-015-9853-1
https://www.csusb.edu/biology/birds/view/535602
