324 RECREATIONS OF A NATURALIST 



phorescent particles. I have long entertained the 

 notion that the alleged luminosity of the breast 

 feathers of the heron is correlated with the so- 

 called "powder-down patches" which have been 

 described as existing not only in the European 

 and American Herons and Bitterns, but in the Night 

 Heron {Nycticorax), Sun-Bittern {Eurypyga), Boat- 

 bill {Cocklearius), Shoe-billed Stork {Balceniceps), 

 Kaku (Rhinochetus), and other marsh-loving birds 

 which are of crepuscular or nocturnal habits. These 

 powder-down patches — so called from the powder 

 which is produced by the pulverising of the barbs 

 of the feathers as fast as they develop — vary con- 

 siderably in the area of the tracts they cover, as 

 well as in their position.^ The Bitterns have two 

 pairs, the Herons three (one in front of the breast 

 and one on each side of the hips between the 

 hips and the tail), while the Boatbill — so called 

 from the singular shape of the upper mandible, 

 which resembles a boat, keel uppermost — has four 

 pairs. It is true they are found in some other 

 birds which do not fish at night, and are placed, 

 not on the ventral, but on the dorsal surface. In 

 this case they probably subserve some other 

 purpose, e.g., to enable the sexes to find each 

 other in the dark. 



As to the evidence that these curious tracts are 

 luminous at night — that is to say, that the powder- 

 down is phosphorescent — it must be admitted that 



1 Messrs Sheppard and Whitear, in their account of Norfolk 

 Birds (1824-1825), noticed that the feathers of the Heron are 

 "frequently loaded with a blue powder." In the American 

 species the powder is said to be yellow. 



