WALTERS J (1988) Breeding data of the Magpie Pica pica. LIMOSA 61 (1): 33-40.

Eurasian Magpie Pica pica Breeding data of the Magpie were collected in two Dutch areas AWD and WHD (c. 25 km apart from each other) in the neighbourhood of Amsterdam in 1977-85. The results, obtained from lowly built nests only, are presented in the appendices 2 and 3, tab. 1-4, and figures 1-3. Breeding success was measured with a method based on Mayfield (1961) and Johnson (1979) (app. I). The daily survival rate of a brood p has a beta distribution according to f(p)=k x p' X (I_p)b, in which a is the numer of brood days under observation, b the number of broods failing in that period, and k a constant. The contribution of failing broods to a is taken to be 40% of the days between the last and the preceding inspection. In the above function the mode or maximum likelihood estimator is p=aj (a+b), the mean p=(a+l)j(a+b+2) and the variance s.d 2 =(a+I)(b+ I)j a+b+2)2(a+b+3) (Abramowitz & Stegun 1970). For the calculation of ? unit standard deviation the skewed beta distributions were normalized by the transformation p,=(l_pn)v, (Bart & Robson 1982). The best values for n appeared to be 2 or 3 for low values of a and b, and 6 or 7 for higher values of a and b. For successful broods the daily survival rate q for individual eggs or young was used to indicate partial losses.

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