van Balen J.H., van Noordwijk A.J. & Visser J. (1987) Lifetime reproductive success and recruitment in two Great Tit populations. ARDEA 75 (1): 1-11

A study was made of lifetime reproductive success (LRS) of parent Great Tits, defined as the number of offspring recruited as breeding birds in the same population. LRS consists of five components: lifespan (LS), number of clutches per year (CY), number of eggs laid per clutch (EC), number of fledglings per egg laid (FE), and number of recruits per fledgling (RF). All components were calculated over the entire reproductive life of a parent. A method of partitioning of variance was applied to measure the relative importance of the components in explaining the variance in LRS. It appeared that RF was by far the most important component, followed by LS. The major role of RF was found in various analyses of subsets of the data, representing different conditions, such as years with and years without a good crop of beechmast, and years with or without an extra supply of seed food. The two study areas, Hoge Veluwe and the island of Vlieland, differ in degree of isolation and, consequently, in the extent of immigration and emigration. Values for RF and LRS are highest on Vlieland. The breeding population in Hoge Veluwe consists for 58% of immigrants. About half of the females (Hoge Veluwe 57%, Vlieland 42%) do not produce any recruits in their life, and 50% of the recruits are produced by only 11% of the females. This illustrates that some females are much more successful than the others. Most of the recruits of a parent are produced in the first reproductive year. Since the level of RF is determined to a large extent by the availability of beech mast, which varies enormously between years, the LRS is maximal for parents that start to breed in a year just before a large beech crop. Part of the differences in LRS between parents is probably caused by individual differences in quality. In the discussion, an attempt is made to relate the observed values of RF and LRS, based on local recaptures, to the real survival and recruitment figures that include settlement outside the area of birth.