156 NEW YORK ZOOLOGICAL SOCIETY. 



among birds. These creatures, handicapped by a vocal language 

 very inferior to our own, and faces, for the most part sheathed, 

 like those of insects in expressionless masks of horn, yet are 

 able by movements of their feathers, limbs, and other portions 

 of the body, to express a wide range of emotions, and to clearly 

 communicate even delicate shades of meaning. 



Interrupting, for a moment, the mention of these finer quali- 

 ties wdiich show the high mental position of birds, it is desirable 

 to emphasize a factor common to all animals, but which in birds 

 is very important, and developed to a remarkable degree — that 

 of extreme individiiality. It is to this plasticity or wide varia- 

 tion on the already high level of knowledge or "platform of 

 determination," as Baldwin happily terms it, that gives to birds 

 the numerous chances for new accidental opp07'tunities, as we 

 may call them — stepping-stones on the road of deduction, to 

 some new and higher expression of psychic power. Every-day 

 accidents in the search for food may be instantly seized upon 

 by the quick perception of birds and turned to good account. 



Birds had early learned to take clams or muscles in their beaks 

 or claws at low tide, and carry them out of the reach of the 

 water, so that at the death of the mollusk the relaxation of the 

 adductor muscle would permit the shell to spring open and afford 

 easy access to the inmate. Probably it needed only the accidental 

 dropping of a few shells on the hard rocks, and a taste of the 

 appetizing morsels within, to fix the habit which, by imitation, 

 has spread so widely amongjairds at the present day. To how 

 trivial an accident might the beginnings, the psychic anlaga, of 

 many modern cosmopolitan traits of birds be traced if we could 

 but read the past clearly ! 



Play and courtship — while they go hand-in-hand, so to speak 

 — afford opportunity for the vast resources of variation to be 

 abundantly expressed. Groos. in his admirable "Spiele der 

 Thicrc," has given five separate classes under the head of court- 

 ship : 



1. Love plays among young animals. 



2. Courtship by arts of movement. 



3. Courtship by display of unusual or beautiful colors and 

 forms. 



4. Courtship by means of noises and tones. 



5. Coquetry in the female. 



In the Zoological Park each spring, and indeed during almost 

 every month of the year, many examples of these courtships and 

 plays can be observed. The dances of cranes and eagles, the 



