page 05 9. Leucism is the lack of melanin (dark) pigments in all or part of the skin, hair, or feathers. It is found in many animal species, and in birds it results in the partial or complete absence of melanin in one or more feathers. The figures show data from a study of leucism in a population of red‑necked nightjars conducted in a national park in Spain from 2016–2020. Nightjars are considered adults when they are two years old and over. Figure 1 Year Number leucistic Total number Frequency (%) Males Females Males Females Males Females 2016 2 2 64 107 3.13 1.87 2017 2 4 74 98 2.70 4.08 2018 2 0 75 108 2.67 0.00 2019 3 3 78 72 3.85 4.19 2020 0 5 43 88 0.00 5.68 Figure 2 numbers above bars are the number of leucistic birds in each age category and sample sizes in brackets bird age (years) frequency of leucism (%) 40 35 30 25 20 15 10 5 0 0 1 2 3 4 5 6 7 8 0 (508)1 (101) 4 (35) 3 (17) 3 (8) 2 (17) 1 (10) 0 (4) 0 (5) Which of the following conclusions about leucism in nightjars cannot be drawn from the data shown? A Leucism occurs at similar frequencies overall in males and females. B The frequency of leucism is low in older birds because leucistic individuals have a greater risk of predation. C The frequency of leucism shows considerable annual variation. D The frequency of leucism increases markedly from the juvenile to the adult stage. [Turn over