42 THE STORY OF THE BIRDS 



some otherwise homogenous groups of birds is 

 most remarkable, and significantly proves with 

 what ease this organ may become modified to 

 meet certain conditions of life. Two of the most 

 striking examples of this are furnished by the 

 Charadriidae or Wading Birds, and the Trochilidae 

 or Humming-Birds. In the former group we 

 have hard chisel-shaped beaks in the Oyster- 

 catchers, sharp and slender ones in the Phala- 

 ropes, Stilts, and Avocets (in the latter upturned), 

 long and sensitive in the Snipes, arched in the 

 Curlews, heart-shaped or spatulate at the end 

 in the Spoonbilled Sandpiper, and absolutely 

 turned towards the right in that singular form 

 the Wrybill. Little less variable is the modi- 

 fication in the bill of the Humming-Birds, and 

 which can only be described as astonishing. Its 

 abnormal maximum length is reached in the 

 genus Docimastes, in which it is longer than the 

 bird, including the head and tail ; whilst its 

 abnormal minimum length attains in the genus 

 Rhamphomicron, in the smallest species of which 

 it is only a quarter of an inch. We find in this 

 family every gradation, from a perfectly straight 

 bill to one so curved or arched as to describe 

 almost one third of a circle, appropriately termed 

 Sickle Bills ; whilst in other species it is strongly 



