The peregrine falcon is undoubtedly one of Ireland’s most impressive birds. A large, powerful falcon it is considered by many to be the ultimate bird-of-prey, diving in a spectacular, vertical stoop to strike its quarry – other birds – in mid air. The peregrine is thought to reach speeds of up to 180 mph as it plummets earthward, though it usually levels off slightly and slows before striking its prey with outstretched talons. The razor-sharp claw of the hind-toe delivers the killing blow with the leg partially flexed on impact. Stricken prey is often allowed to drop to the ground before the raptor circles back to collect its prize.
In the summer months peregrines can be seen around the coastal cliffs, mountain crags and inland quarries on which they breed. In winter they frequent favourite hunting grounds like moorland, marshes and estuaries, where pandemonium amongst other birds often heralds the approach of these supreme aerial hunters.
The peregrine is around 45cm (17½ inches) long with a robust build. Adults are a dark, blue-grey above and white below. The breast is barred with black – with the much larger female showing more prominent barring than the male. Peregrines have a distinctive moustache of dark plumage either side of the face that stands out against the pale breast and cheeks. Juveniles have browner plumage than the adults, a less prominent moustache and have vertical streaks rather than horizontal bars below. Flight is generally a series of rapid wing-beats followed by a prolonged glide. The bird also spends long periods perched, shoulders hunched, ever watchful.
Peregrine populations were severely affected by the widespread use of organochlorine pesticides like DDT during the 1950’s and 60’s. At the time these pesticides were commonly added to seeds. While these seeds contained a relatively low quantity of pesticide the chemicals became concentrated in the tissues of pigeons and other birds, which ate the treated seeds in large numbers. Peregrines would then eat numerous contaminated birds, resulting in a further concentration of the pesticide in the falcons. While not always lethal to the adult birds, these high concentrations of pesticide would render them sterile or caused them to lay very brittle eggs that shattered under the weight of the female as she tried to incubate them. Peregrine numbers plummeted to dangerously low levels.
Since the 1970’s a ban on these pesticides has allowed peregrine populations to slowly recover across much of their northern European range, including here in Ireland, where we now have an estimated 265 breeding pairs in the Republic and a further 100 pairs in the North. Peregrines rear a single brood of chicks each year. Between April and June the female lays three to four buff-coloured eggs with red speckles on the nest site or eyrie, typically a rocky ledge on a steep cliff-face. Incubation takes around twenty-eight days and the young birds fledge between thirty-five and forty-two days after hatching.
During the winter months peregrine numbers increase considerably as birds from further north in their range visit Ireland, following their migratory prey species south. For many people the winter months offer the best chance of spotting a peregrine as the birds patrol the skies over estuaries, mud flats and coastal waterways around the country.