Sir: I hate to disillusion Colin Dunn (letter, 23 February) but the 3:1 ratio of males to females in the mallard population of the Barbican has been the norm throughout the 15 years I have worked there.
In spring, the young drake's fancy turns to gang-rape; the outnumbered females are dive-bombed by one drake after another. Afterwards the duck becomes a typical unsupported single mother. Unlike most other male birds, the mallard drake plays no part in the process of building the nest, incubating the eggs or feeding the nesting duck.
Between 1983 and 1988, when ducks regularly nested on the balcony outside my office window, there were generally one or more eggs in each clutch unhatched. This may be because the duck has to leave the nest to get water and food for herself, and if she makes the mistake of nesting on a seventh- storey concrete ledge she has to fly some distance. Sometimes she seems to have trouble finding her way back, and the eggs are deserted altogether.
According to naturalists, the surplus males are usual in the British mallard population in town and country, and the only reason the residents and workers of the Barbican notice it more is because human and bird live at close quarters there.
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