(1) The relationship between habitat, chick growth, fledging size and fitness of breeders was studied in two populations of carrion crows, Corvus corone corone L., one living in an urban and another in an agricultural environment in south-western Switzerland. The logistic equation was used to model weight gain and tarsus growth, and the growth constant (k) and the asymptote (a) computed, using an iterative least square fitting technique. The chicks in the two habitats are compared with respect to the parameters a and k of the logistic equation. The Darwinian fitness is evaluated for each habitat. (2) Chicks in the urban habitat gain weight slower, take longer to reach fledging weight and are significantly lighter at fledging than the chicks in the agricultural habitat. Thus, for the weight curves, the chicks in the urban habitat show significantly lower values for both parameters a and k. (3) Tarsus growth is slower for chicks in the urban habitat, but in contrast to weight gain, growth of tarsus is not prolonged. For tarsus growth the parameter k is identical in the two habitats, but urban chicks show significantly lower values for the parameter a. Tarsus length is fixed by the age of fledging. Chicks in the urban habitat have shorter tarsi at fledging. (4) Growth of wing is slower in the urban habitat, but, since wing length is incomplete at fledging, no curves were fitted. (5) Tarsus length of territory-holding adults was measured in both habitats and a critical minimum size for territory acquisition empirically established. Of all fledglings raised in the urban habitat, 79% fall below this critical size and will therefore be unable to acquire a territory and thus be excluded from breeding, whereas only 24% of fledglings raised in the agricultural habitat will be excluded. (6) Successful parents in the agricultural habitat fledge, on average, 2.7 chicks per year, parents in the urban habitat 1.5 chicks only. 36% of all territory holders in the agricultural habitat fledge young, 39% in the urban habitat. Since a much higher percentage of fledged chicks reach the critical body size in the agricultural habitat, these parents reach a Darwinian fitness five times higher than the parents in the urban habitat.