Female sparrowhawks can weigh twice as much as their mates
In most mammals the male is the bigger sex. Sparrowhawks flip that. A female can be a quarter larger than her partner and up to twice as heavy, one of the widest gaps between the sexes in any bird. The pair even hunt different prey: he takes tits and sparrows, she takes thrushes and starlings.
The Eurasian sparrowhawk is a small woodland hawk with short, broad wings and a long tail, built for weaving between trees at speed. Adult males are slate or bluish grey above with fine orange barring below; females and young birds are brown. Its pale belly and dark back are countershading, which breaks up its outline, and its horizontal barring is typical of forest raptors. It flies with a distinctive flap, flap, glide.
Everything about it is tuned to catching birds. The small bill is used for plucking and tearing, not killing. The legs and toes are long, and the middle toe has a bump underneath that lets it close without a gap, improving the grip. Females can tackle prey of 500 grams or more. In Britain, birds further north are larger, with wing length increasing slightly for each degree of latitude. Cuckoos seem to exploit its fearsome look: their barred bellies resemble a sparrowhawk's, and small birds hesitate to approach them.
It nests in a twig platform up to 60 centimetres across. The female lays four or five eggs and stays heavy while the male feeds her; the chicks hatch after about 33 days. Only 34 percent of young survive their first year, and a typical lifespan is four years. After the Second World War the population crashed as organochlorine seed treatments accumulated in its prey, killing some hawks outright and leaving others laying eggs with shells that cracked. Once the chemicals were banned it recovered, and it is now among Europe's commonest birds of prey, with roughly 1.5 million worldwide in 2009.
Pigeon fanciers and gamekeepers have long resented it, yet studies of racing pigeon deaths blamed sparrowhawks for less than 1 percent. Falconers have flown it since at least the 16th century, finding it hard to train but brave. Its Latin name recalls Nisus, a Greek king turned into a sparrowhawk.
Source: Eurasian sparrowhawk
