Life and death of a glamorous predator

A NOTE from the British Trust for Ornithology (the ‘BTO’) says that a sparrowhawk, ringed by me, has been found in Malahide.

The find is a bit of a surprise. Even catching a hawk is a special event, let alone getting a ring back. In 25 years of ringing I have handled only half a dozen sparrowhawks.

They are caught very rarely, usually as a result of their Pearl Harbour-style hunting technique, a sudden surprise attack from the air. A hawk will perch in a tree, or wheel about high in the air watching for small birds in bushes or on the ground. Spotting a potential victim, the hawk drops down almost to ground level.

Then, sweeping fast and low, hedge-hopping over obstacles like a Dam-buster’s bomber, it strikes its target. Sometimes the victim sees the hawk coming and an aerial chase ensues; sparrowhawks are superb aerial acrobats.

Mist-nets are almost invisible. They resemble giant spider’s webs stretched between poles. Birds failing to see them get caught. Sparrowhawks, with their superior eyesight, should be able to spot the trap but, in the excitement of the chase, some fail to heed the danger. I’ve caught hawks with birds in their talons. Perhaps the victim was already in the net and the hawk went in to get it, trapping itself in the process, or the two were caught together in flight.

Catching a hawk is a thrilling experience. The bird struggles to free itself from the net and many escape before you reach them. Nor is handling hawks a task for the faint-hearted; these are tough customers. The long needle-sharp talons sink into your flesh but, with the adrenaline flowing in the bloodstream, you hardly feel the pain.

It’s said that soldiers in battle can lose limbs and yet feel nothing; sparrowhawk catching is a bit like that. The hawk, once extracted from the net and its lethal talons prised from the hands, is put into a cotton bag. Both bird and ringer now have a chance to calm down.

Selecting the correct ring is not always straightforward. Female sparrowhawks are larger than males. They take a bigger ring, so you must be sure of the bird’s sex before proceeding. The sex of a young hawk can be difficult to determine; males and females look alike. The only reliable way to tell them apart is to measure the lengths of wing, leg and bill.

With mature adult birds telling the sexes apart is not a problem. Females are grey-brown on the back and have horizontal brown bars across the pale breast. Males are much more glamorous; blue-grey on the back with bright reddish barring in front. In parts of England the male is known as the ‘blue hawk’. Falconers refer to males as ‘muskets’. The gun was named after the hawk, not the other way round.

But whether it’s a male or a female, an adult or a juvenile, holding a sparrowhawk in your hand is a thrilling experience. The bright lemon-yellow eyes with their shiny black pupils are stunning. Old male hawks are said to have orange-red eyes, but I have not been lucky enough to catch one of these veterans. That females are bigger than males may seem odd, but actually it isn’t. It’s the bias among mammals and birds towards having larger males that’s strange. From the physical standpoint, reproduction is almost entirely a female function; all the male does is kick-start the process. An egg with its yolk, albumen and membranes is thousands of times heavier than a sperm and requires much more resources on the part of a would-be parent to produce it.

Pregnancy in mammals and incubation in birds require huge expenditures of energy for the expectant mother. That females should be larger seems logical and among spiders, baleen whales and birds of prey, they are. Why most other animals don’t follow suit is a puzzle. There is a bonus in having different sizes; competition between the sexes in the search for food is reduced. Male sparrowhawks, for example, hunt mostly sparrow-sized birds, whereas females prefer starlings or thrush-sized ones. Birds as big as pheasants are taken occasionally.

Catching a sparrowhawk may be a stroke of luck, but the odds against a ringed one subsequently coming to light are very low indeed. Between 1909 and 2005, 44,916 sparrowhawks were ringed in Britain and Ireland. Only 4,311 were found subsequently.

The time between ringing and the finding of the Malahide hawk was just under five years. As the bird was an adult when ringed, it must have reached at least the age of seven. Not many hawks survive as long as this one. Only about 30% of chicks leaving the nest are alive a year later, and the life-expectancy from then on is about a year and a half. The oldest hawk ever recorded by the BTO was ringed in Hampshire in July 1982 and found, 48km away, in Leamington in September 1999, 17 years later. The Malahide bird was not a great traveller; it died only 2km from where it was ringed. Our hawks seem to lead rather sedentary lives.

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