how is this considered hiding methods?

[Gor Gyolchanyan]

Can someone please tell me why the following code gives these 
errors?

Error: class main.BirdZoo use of main.VertebrateZoo.take(Animal 
animal_) hidden by BirdZoo is deprecated

Error: class main.ParrotZoo use of main.VertebrateZoo.take(Animal 
animal_) hidden by ParrotZoo is deprecated

/// The code:

        class Animal { }
        class Vertebrate { }
        class Bird: Animal { }
        class Parrot: Bird { }
        
        class VertebrateZoo
        {
                void take(Animal animal_)
                {
                        if(auto vertebrate = cast(Vertebrate)animal_)
                                take(vertebrate);
                }
                
                abstract void take(Vertebrate vertebrate_);
        }
        
        class BirdZoo: VertebrateZoo
        {
                override void take(Vertebrate vertebrate_)
                {
                        if(auto bird = cast(Bird)vertebrate_)
                                take(bird);
                }
                
                abstract void take(Bird bird_);
        }
        
        class ParrotZoo: BirdZoo
        {
                override void take(Bird bird_)
                {
                        if(auto parrot = cast(Parrot)bird_)
                                take(parrot);
                }
                
                abstract void take(Parrot parrot_);
        }