01834naa a2200217 a 450000100080000000500110000800800410001910000210006024500720008126000090015352012650016265000150142765000100144265000160145265300110146865300180147965300180149770000200151570000170153577300640155217956431999-05-05       1978    bl ---       0--  u    #d1 aMAGNUSSON, W. E.  aA double-survey estimate of population size from incomplete counts.  c1978  aThe problem of estimating the size of a population from "total counts" known to be inaccurate has been approached from several directions (Table 1). The first 3 are applicable when the entities being counted cannot be distinguished individually, but each of these methods suffers from the requirement that the population is counted, albeit incompletely, on numerous occasions. The effort required is daunting. Caughley (1974) showed that only 2 counts were needed when entities could be identified individually such that the tallies of 2 equally skilled observers could be dissected into those seen by one or other observer and those seen by both. The method was illustrated by Eltringham's (1972) data on groups of elephants (Laxodonta africana) counted and mapped independently by 2 observers during a "complete count" from the air. This note extends that method by dispensing with the requirement that the probability of a given entity being seen by onde observer is the same as its being seen by the other. Hence the method is now generalised to allow for the 2 counts being made by different methods of survey. We will give an example of its use in which nests of the crocodile (Crocodylus porosus) are counted and mapped from the air and from the ground.  apopulation  aCenso  aPopulação  aCensus  aDouble-survey  aDupla amostra1 aCAUGHLEY, G. J.1 aGRIGG, G. C.  tJournal of Wildlife Managementgv.42, n.1, p.174-176, 1978.