1914 J Wetmore, Development of the Stomach in Euphonias. 459 



In ray work in the field I soon learned that the Euphonias fed 

 eagerly on mistletoe-berries of the genus Phoradendron, clumps of 

 which were locally common in tree growth. This habit was well 

 kown to the Porto Ricans and has been reported from various 

 islands in the Lesser Antilles where these birds are known as " mis- 

 tletoe birds." From their restless activity in the tree tops I was led 

 to believe that they were feeding on insects as well but in the critical 

 examination of the stomachs, seeds of three species of Phoradendron 

 and one other of an allied Loranthaceous genus were encountered 

 alone with absolutely no trace of animal matter. The globular 

 berries of these mistletoes have a moderately tough skin contain- 

 ing a seed surrounded by a yellowish-green transparent fluid, 

 gelatinous in appearance and exceedingly viscid. In feeding the 

 Euphonias break this outer skin with their bills and swallow the 

 single seed surrounded by its adhesive pulp. The seeds pass 

 through the intestinal canal wholly undigested and the whole mass is 

 excreted in apparently the same condition as when it was swallowed, 

 as the ffeces are amorphous and exhibit practically none of the 

 white nitrogenous renal matter commonly noticed in other birds. 



Though the adhesive pulp surounding the seed is apparently 

 unchanged by the processes of digestion yet we know that some 

 part is taken from it. A large per cent of it is composed of viscin — 

 or as it is popularly called bird lime — and several gums, and these 

 act as a vehicle for various salts of potash, lime and magnesia, vege- 

 table acids and oxide of iron a highly tonic purgative combination. 



Arabine present in the gums is readily dissolved, furnishing grape 

 sugar, other nutritive matter is contained and with the various 

 salts, of the highest importance to the body, is readily assimilated. 

 Thus mistletoe apparently furnishes a highly nourishing food from 

 which the nutritious elements are easily separated by the digestive 

 juices without preliminary grinding and trituration. A consider- 

 able amount of bassorin which is contained in the bird-lime is 

 insoluble in ordinary fluids while in water it becomes viscous which 

 accounts for the lack of change in appearance of the food in passing 

 through the alimentary canal. In captivity this bird thrives on a 

 diet of over-ripe banana, a food which, Hke the mistletoe berries, 

 can be assimilated readily without mechanical comminution. 

 In a wild state however it eats only the mistletoe berries. 



