Wikipedia: The Mallard is 56–65 cm long, has a wingspan of 81–98 cm, and weighs 0.9–1.2kg. The breeding male is unmistakable, with a green head, black rear end and a yellowish orange (can also contain some red) bill tipped with black (as opposed to the dark brown bill in females). The female Mallard is light brown, like most female dabbling ducks. However, both the female and male Mallards have distinct purple speculum edged with white, prominent in flight or at rest (though temporarily shedded during the annual summer molt). In non-breeding (eclipse) plumage the drake becomes drab, looking more like the female, but still distinguishable by its yellow bill and reddish breast.
The Mallard inhabits most wetlands, including parks, small ponds and rivers, and usually feeds by dabbling for plant food or grazing; there are reports of it eating frogs. It usually nests on a river bank, but not always near water. It is highly gregarious outside of the breeding season and will form large flocks, which are known as a sord.
Mallards form pairs only until the female lays eggs, at which time she is left by the male. The clutch is 8–13 eggs, which are incubated for 27–28 days to hatching with 50–60 days to fledging. The ducklings are precocial, and can swim and feed themselves on insects as soon as they hatch, although they stay near the female for protection.
Mallards also have rates of male-male sexual activity that are unusually high for birds. In some cases, as many as 19% of pairs in a Mallard population are male-male homosexual. (!)
When they pair off with mating partners, often one or several drakes will end up "left out". This group will sometimes target an isolated female duck — chasing, pestering and pecking at her until she weakens (a phenomenon referred to by researchers as rape flight), at which point each male will take turns copulating with the female. Male Mallards will also occasionally chase other males in the same way. (In one documented case, a male Mallard copulated with another male he was chasing after it had been killed when it flew into a glass window.
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As for the leaf in the windshield wiper, it has great metaphorical significance only to me, and I have been sworn to secrecy. I'll say only that it concerns my relationship with a woman.