The feeding habits of living birds are diverse, including fishing experts such as Osprey. Interestingly, as early as the Cretaceous about 90 million years ago, there was also a "fish killer" called fish and birds. The reason why paleontologists call it fish and bird is obviously that this ancient bird similar to the size of seagull ate fish for a living. Fish and birds are famous extinct ancient birds in Cretaceous.
As early as the end of the 19th century, its fossils had been discovered by paleontologists. Because the fossils were found in the marine strata of North America, it is speculated that fish and birds mainly move along the coast. They have strong wings and developed sternum, so they should have high flying ability. In addition, they have long mouths and sharp and curved teeth in their mouths. Moreover, their fossils are usually preserved with a large number of fish fossils. Therefore, it is speculated that the main food of fish and birds is marine fish.
Living in the late Cretaceous in North America, about 80 million years ago, dusk birds, like today's penguins, fish by diving. Paleontologists discovered this large diving bird about 1.5 meters long at the end of the 19th century. Fossil evidence shows that dusk birds still retain a lot of teeth in their mouths, have leafy fins on their feet, and their wings have been very degraded. It is obvious that they have lost the ability to fly, but their hind limbs are developed. They are probably birds that dive in shallow waters and mainly prey on fish.
Fish and evening birds are not the oldest fish eating birds. In the early Cretaceous strata in China, about 120 million years ago, Chinese paleontologists have found several fossils of ancient birds that eat fish. They provide more conclusive evidence that ancient birds ate fish. The most famous one is named swallow bird. It is smaller than fish and birds, but it also has strong flying ability and very developed teeth. According to the skeletal characteristics of swallow birds' feet, it can be inferred that they mainly live by the lake. What's more interesting is that some swallow bird fossil specimens still have undigested fish remains in their stomach, and one specimen also shows swallow birds swallowing fish.
In the early stage of bird evolution, fish eating birds also represent the most advanced species, perhaps because the high energy obtained by fish helps them fly better, and finally evolved into living birds step by step.