C L A S S I C A L O P E N - P O P U L AT I O N M O D E L S 45 The estimate of population sizes then follows and is the same as that de- rived earlier in equation 3.4, namely ^ Mn ^ ^ ^ N i = U i + M i = i i m i Note that in this formulation the population sizes and birth numbers do not appear in the likelihood directly and are derived parameters. The Cormack-Jolly-Seber Model In some cases all components of the likelihood are combined in the gen- eral JS model as we just described. However, in other cases the CJS model may be used alone to estimate survival and capture probabilities (Cormack 1964). This CJS model requires information on only the re- captures of the marked animals, and that the marked animals be repre- sentative of the population. In some cases the marking process may use a totally different method of capture than the recapture process, as with mark­resight studies. See, for example, Pollock et al. (1990, p. 51) for a description of a mark­resight study on Canada geese. The dependence,