37
 between rookeries in northcentral Florida and rookeries in

 south Florida during the same period indicated that

 conditions for raising young were enhanced by greater

 fJulctuation of the water table, causing greater

 -concentration of food. The probability of nesting failure

 with zero production in certain years was, however, also

 increased in areas where the water level fluctuation was

 the greatest.

 Table 2 gives the number of fledglings produced at the

Wood Stork rookery at Corkscrew Swamp Sanctuary for the

past 19 yrs. As the Corkscrew population represents

approximately one half the Wood Stork population in the

United States (J. Ogden, pers. comm.), this table provides

a good index of the variation in the size of the nation's

Wood Stork population over this period. As the table

shows, a high percentage of nests were successful in only 7

out of 19 yrs. In 7 other years out of the 19, no young

were produced, either because nesting was not attempted or

because all the nests were abandoned before the young were

old enough to support themselves. In the other 5 yrs only

a small portion of the population successfully raised

young.

 Kah1's (1964) observations, augmented by a comparison

of the fledgling production record at Corkscrew with the

weather record for the same period, suggest that successful

nesting for Wood Storks in this area depends on the

following factors: -..