RELATIONS TO ANIMATE ENVIRONMENT 115 



nature, birds must have played no inappreciable part in keeping 

 in check the prodigious fecundity of gregarious fishes, both fresh 

 and salt water ; and blundering -efforts made to-day by certain 

 ill-informed would-be legislators to keep down fish-eating birds, 

 on the ground that they lessen our food supply, fail of their 

 purpose. For should they succeed in appreciably reducing the 

 numbers of these birds, they will but give a fresh impetus to the 

 shoals of predaceous fishes which would profit by the increased 

 abundance, and over these they have no control whatever. 



The Secretary-bird, the New-World Vultures, and certain 

 species of Kingfishers may serve as examples of birds which 

 contribute more or less effectually to keep in check the undue 

 increase of reptiles. 



The Secretary-bird {Serpentarius reptilivorus) of S. Africa, 

 from its fondness for poisonous snakes, has during the last few 

 years been carefully protected by law. Standing nearly four 

 feet in height and of powerful build, this remarkable bird — an 

 aberrant member of the Hawk tribe — displays no small skill 

 and caution in attacking its venomous prey, shielding itself by 

 means of the wings, and kicking violently with both feet until 

 its victim is vanquished. The " Turkey-buzzard" of the Genus 

 Cathartes — more commonly known as the Turkey-buzzard or 

 Turkey-vulture — like the Secretary-bird is an aberrant member 

 of the Accipitres. By preference a Carrion-feeder, this bird, 

 however, confers yet other benefits by its fondness for the eggs 

 of the alligator. In this it displays great cunning, watching 

 the process of deposition, and pouncing down upon the prize so 

 soon as the unsuspecting reptile has taken to the water. 



We have been considering birds in relation to their animate 

 environment only in so far as they directly influence this, in 

 so far as they may be regarded as affecting the balance of 

 organisms other than birds. But we may turn now to another 

 aspect of the picture, or rather, to the complementary picture, 

 which shows us how this animate environment reacts upon the 

 birds. 



This reaction appears to obtain only between the birds and 

 their animal environment, and different groups of birds on one 

 another. And instances of this phase of bird-life will only be 

 cited where this reaction is exhibited in what may be called a 

 measurable quantity. 



