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<br />TABLE IV <br /> <br />AVERAGE WHOOPING CRANE HATCHING RATES AND DEATH RATES: 1938-1976 <br /> <br />Hatching Rate <br />Average Std. error <br /> <br />Death Rate <br />Average Std. error <br /> <br />1938-1947 0.206 0.029 0.169 0.053 <br />1948-1957 o . 163 0.037 O. 149 0.037 <br />1958-1967 0.154 0.027 0.103 0.018 <br />1968-1975 0.111 0.022 0.065 0.025 <br /> <br />Note: These rates are derived from the annual count of cranes conducted by <br />the FWS at Aransas NWR every winter, 1.n which the number of adult birds and <br />the number of newly hatched chicks are tabulated. (After one year, the young <br />cranes are indistinguishable from adults.) Obviously, this does not count all <br />chicks, but only those that survive the migration back from Wood Buffalo <br />National Park. <br />If Ct and Yt are respectively the total number of cranes and the <br />number of newly hatched chicks observed in year t, then t~e hatching rate is <br />de fi ned by <br /> <br />Hatching Rate <br /> <br />Yt <br />=- <br /> <br />Ct-1 <br /> <br />(1) <br /> <br />The number of deaths Dt during year t can be inferred from the population <br />data: <br /> <br />Dt = Yt (Ct - Ct-l). <br /> <br />(2) <br /> <br />The death rate is defined to be: <br /> <br />Death rate = D <br />t <br />C <br />t <br /> <br />(3) <br /> <br />44 <br />