ornithologist
He/she is an ornithologist.Someone that studies birds is called an ornithologist.An ornothologist
The name of a scientist that studies sports is called a sports scientist.
An ornithologist is a scientist that studies the branch of zoology that concerns birds. If he specialized in ducks he would be said to specialize in Anatidae (the family of birds which includes ducks)
An arachnologist
A scientist who studies crystals is known as a Crystallographer.
A scientist who studies animals is called a zoologist.
A scientist who studies animal life is a zoologist. There is no particular name for a scientist that specialises in platypuses.
The name for this type of scientist is a teuthologist
This answer is a entomologistA scientist who only studies fish is called an ichthyologist.
environmentalist
ecologist
Astronomer