The Incubation Period of the Clapper Rail
The Incubation Period of the Clapper Rail-In her review of incubation periods of North American birds, Nice (Condor, 56, 1954:182-183) pointed out the present inadequate knowledge of the incubation period of the Clapper Rail (RalZus Eongirostris). I have two observations on incubation period of this rail on San Pablo salt marsh, Richmond, Contra Costa County, California. In 1951 a clutch of 9 eggs was completed on April 17 and the last egg hatched on May 10; in 1953 a clutch of 8 eggs was completed on March 28 and the last egg hatched on April 20. In both clutches the incubation period was therefore 23 days. The period of hatching was somewhat less than 24 hours for both clutches. Thus, in view of the fact that hatching can take as long as 48 hours in Clapper Rails of the Atlantic coast (Nice, op. cit.:183), some records of 24-day incubation periods may well be expected.-RICHARD F. JOHNSON, Museum of Vertebrate Zoology, Berkeley, California, December 12, 1955.