Avian Predator Peregrine Falcons

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The brown and gold head of a male Coqui Francolin tilted upwards as we aimed our telephoto lenses. 'Keah, keah' came the wail above our heads, diverting us from this tantalizing opportunity, and a Peregrine Falcon swooped over the mountain acacia woodland before landing on a dead tree some 15 metres away. We failed again with the lenses as the falcon dropped off the branch a moment later, sailing in front of the huge sandstone cliff of the Chizarira escarpment. 'Keah, keah' she wailed again, and then 'eechip, eechip, eechip chip' was heard from the male as he delivered a plucked bird in mid air. She took it in her claws and flew along the cliff and around a buttress. We lost that opportunity as well, unable to mark exactly where she had gone.

Arthur Dunkley and I were surveying and monitoring falcon breeding in the Sebungwe region of Zimbabwe in 1986. Below us lay the Zambezi Valley, dry deciduous woodland with patches of mopane forest and baobabs. Access to the area was on foot, mainly along ancient elephant trails. The huge pachyderms still wandered extensively throughout a region that is the current destination of many subsistence farmers. The eradication of the tsetse fly by the spraying of DDT has accelerated this immigration over the past ten years, and the recent completion of a tar road through Gokwe has speeded it up even more.

Our particular concern at the time was the rare Taita Falcon, especially as two Taita nests found in 1984, only two kilometres apart, appeared to have failed then and over successive seasons. Wherever there have been Taitas, Peregrine Falcons have been found alongside them at higher densities. We suspected that the recent spraying of DDT was a key problem in the failed breeding attempts, but had no hard data to support this. The river systems of Chizarira drain into Lake Kariba, about 60 kilometres away, and some eggs collected from African Fish Eagles along the lake shore and from African Goshawks in the woodlands nearby had significant levels of DDT and its metabolite DDE. Already shells were thinning, but the ultimate test is productivity: are the adults producing young?

We were at Sebungwe to find out. Well positioned on the buttress, we spotted the next food delivery about an hour later, and the falcon took another plucked bird into the huge sandstone face, landing at the edge of a slit about halfway down. Two downy white chicks were tucked at the back of the well-shaded recess and soon they were being fed small pieces of meat ripped from the carcass by the adult and proffered gently in her beak to the eager youngsters. Four years later, a single egg was removed from this pair, as part of a nationwide survey on the impact of DDT on the Peregrine Falcon. The pair successfully raised a single chick from the two eggs remaining, but analysis of the sample indicated seriously high levels of DDT and DDE, significantly higher than for any of the 12 other sites surveyed in the country. Although the highest levels of contamination were found in the Zambezi Valley, the productivity of Peregrine Falcons there has not yet shown a meaningful decline.

In Zimbabwe, Peregrines can be found virtually anywhere, from First Street in the city of Harare to Victoria Falls. However, they are most abundant in well-wooded parts of the Zambezi Valley, where 37 per cent of 136 nest sites have been found along escarpments, gorges and inselbergs. Here they sometimes outnumber the Lanner Falcon 10 to one, whereas on the granite shield of the highveld and middleveld the Lanner is usually more common, especially in degraded areas where woodland has been cleared for cultivation, making conditions infinitely more favourable for the generalist.

Of the two species, the Lanner has a more catholic diet, which includes rodents and reptiles as well as birds, since its lower wing loading allows it to hunt effectively on the ground. By contrast, the Peregrine is a specialist with a high wing loading, feeding almost exclusively on birds taken on the wing; it rarely takes quarry on the ground. Furthermore, Lanners often breed on koppies and small clustered boulders of granite called tors, which are avoided by Peregrines. However, both species compete for nesting sites on large domed inselbergs.
The optimum breeding areas for Peregrines in Zimbabwe are cliff sites in well-wooded country within striking range of river systems, where they are more successful than Lanners. In this dry habitat their avian prey is forced to fly over the canopy to water, and the river systems also offer natural corridors over which some species fly. A falcon relying on high-speed attack, the Peregrine can intercept such prey over the top of the canopy more effectively than the Lanner can, and its much bigger feet with a long middle toe, adapted for clutching prey in the air, give it an additional advantage over its rival.

The Lanner is probably constrained by closed canopy woodland, which reduces its opportunities to take ground prey, but it makes better use of more open habitats where avian prey is scarcer. Indeed, it is in open areas that the Lanner has developed a predilection for young poultry, common in degraded communal lands where kraals are frequent. In the Matobo Hills Lanners are more common in the communal lands than in the neighbouring national park! A few subsistence farmers have learned to trap problem Lanners, using falconry techniques such as nets. Once I received an immature Lanner from the Matobo Hills area caught in this way.

The Peregrine is well known for its occupation of cities, with breeding reported also from Nairobi and Cape Town. When a pair monitored by the Zimbabwe Falconers' Club (ZFC) in Harare lost two of their eggs, two captive-bred young were placed in the nest. Publicity surrounding this action led to some useful public involvement, as both fledglings had problems when they left the nest. It is not unusual for newly fledged young to experience difficulties, as streets in the central business district are like canyons. If the fledglings plummet down to street level, there are few hiding places for them, and traffic is a hazard. Adults trying to feed youngsters on the ground are also placed at risk. In Bulawayo, an immature female was recovered injured on a street, waterlogged and in egg lethargy. She laid an egg in captivity a few days later. The following year another immature female bred in the city, producing a clutch of three eggs which were eventually found broken.

Peregrines which have made their home in cities sometimes collide with buildings whilst hunting their prey, and I have had the opportunity to study four such individuals from Harare. A male was stunned and broke his maxilla after colliding with a plate-glass window at the Monomotapa Hotel. A female, stunned when she flew into a plate-glass door at the veterinary research laboratory, was treated and then trained successfully for falconry. She was subsequently used in captive breeding and had produced 30 young by the time she died at the age of 15 years. An adult female from a known breeding site in the city died after striking a plate-glass window. She was soon replaced, indicating a healthy population around the city. The fourth victim was an immature female found dead inside the headquarters of Founders Building Society. The employees, noticing a broken window with the shattered glass inside the office, suspected that the building had been broken into. Instead they found the body of the Peregrine, which had managed to smash through plate glass eight millimetres thick! It is almost certain that it struck the window during a high-speed chase after prey.

Another hazard of urban life for Peregrines is being shot at, as they sometimes are when they attack pigeons at lofts. I was sent the carcass of an immature male Siberian Peregrine that had been peppered with bird shot at the Borrowdale racecourse in Harare. This was only the third specimen of the species for Zimbabwe: in 1960 a museum collector took an adult male (chasing a Hadeda Ibis) near Birchenough Bridge, and in 1981 a falconer was given an immature male that had been rescued from the protective net screen over a radar mast at Thornhill Air Base.

Records of prey items taken by Peregrines in Zimbabwe include 79 species of birds. By number, the largest proportion, 39 per cent, were doves and pigeons, while rollers, hoopoes and hornbills made up nine per cent, starlings also nine per cent, swifts five per cent, and small seed-eaters 11 per cent. Birds as large as an adult Helmeted Guineafowl have been reported, but the most unusual prey item was an unidentified bream, recovered from a pellet in a nest which had three young! Insect-eating bats are also a great attraction for the Peregrine, especially as both the bats and the falcons are active during crepuscular hours. As little evidence of these small bats remains at feeding points (other than from pellets), the significance of this prey may be underestimated.

Brightly coloured birds such as rollers are an obvious target for the Peregrine, but flocks of Red-billed Queleas are also a great attraction, and queleas can figure significantly in its diet. Hunting large flocks requires a deliberate strategy, whereby the Peregrine stoops at, but not through, the mass of birds, trying to split some away as clear and unprotected targets. Several attempts are usually necessary, as the prey tries to bunch together.

Peregrines are renowned for their stoop, which they can start from a height of 300 metres or more. It seems that few prey species are able to detect them at this height, and once, bullet-like, the falcon is on its way, it is often too late for its quarry to escape, even if it has spotted its attacker. In level-pursuit chases too, Peregrines are fearsome hunters, generating a great turn of speed which they can maintain for relatively long distances. Some pursuits continue high into the sky in what falconers term 'ringing flight'. I watched enthralled one afternoon as an adult male engaged a Crowned Plover, locking on like a missile. The slower-flying plover used its superior agility to great effect, evading each strike as it mounted to some 150 metres before descending in a series of elastic stoops and throw-outs, the Peregrine just too fast and headlong to match it as they eventually planed over the bushy surface and out of sight. The falcon can be out-manoeuvred by other prey species too. I have watched a trained Peregrine fly itself to exhaustion in pursuit of an African Hoopoe, a particularly slow-flying bird which more than makes up for its apparent disadvantage by its ability to stall and flit above the speedy falcon. A fieldworker described a similar result when a pair of adult Peregrines in the wild pursued an African Hoopoe in tandem.

Waterholes, springs and cattle feedlots often attract enormous numbers of small birds and doves, and these in turn attract Peregrines. One Peregrine nest site is just 12 kilometres from a feedlot and either of the adults can be seen almost daily at this spot, which hosts thousands of doves. Some Peregrines, however, travel as far as 20 kilometres from their nests for food. This occurs in parts of the Save Valley, where the birds' breeding sites overlook an extensive belt of deforested land. Whilst camping on the banks of the Save River, I have observed several times a pair of Peregrines flying in from the mountains east of the river where there are known to be eyries, and on one occasion I witnessed a pair co-operatively hunt a Cape Turtle Dove before the female made the kill and took it into a dead tree to feed. In the same location one of my trained Peregrines was able to poach a Double-banded Sandgrouse from a wild Peregrine. The Save area has seen a decline in the Peregrine population over the past 20 years and some traditional nest sites now host Lanners.

In Zimbabwe Peregrines nest on cliffs, although there is a single record of tree-nesting near Masvingo. This is highly questionable, probably a result of confusion with the Lanner which often uses old stick nests in trees. High cliffs are favoured, but many nests have also been found on modest ones, where there is as little as 30 metres of vertical cliff face. In fact a few sites were virtual 'walk-ons', even in areas populated by baboons which are likely predators. One nest was located in an old antbear hole on an incline above a 100-metre cliff, where there were other, more traditional nesting sites. Another pair used an open ledge just half a metre below an easily traversed knife-edge ridge where an observer nearly stood on a chick. On a 30-metre-high cliff a pair nested in a small hole just below the top. As all of these sites fledged young, the Peregrines clearly relied on their cunning to escape detection. Sheltered ledges, especially cavities and caves, are preferred sites.

Eggs are usually laid from the end of July to early September. Two to four are laid in a scrape of dirt, or sometimes in an old stick nest that previously belonged to a Black Eagle or Black Stork. The female is particularly defensive of the site, making frenzied attacks on intruders (including human ones) when it has young. The chicks usually fledge towards the end of October and remain around the nesting area for a further six to eight weeks, but this can vary. Watching fledged young Peregrines frolic around the nest can be a wonderful experience, as I discovered early one December when, in the Zambezi Valley, I was treated to some expansive acrobatics from three juvenile Peregrines at their eyrie site. Exploiting the immense updrafts against the cliff during mid-afternoon, the youngsters were totally uninhibited as they swept above the cliff directly in front of me. Randomly they folded their wings and stooped some 300 metres towards the woodland below, then swung up in a tight arch, sitting on their tails.

On another occasion, while I was scrutinizing a Taita nest site in the Batoka Gorge below Victoria Falls, the wailing call of young falcons attracted my attention. A x20 spotting 'scope revealed four fledged birds around a ledge near the top of the cliff, but they were Peregrines! Just then an adult Taita was spotted flying across the gorge towards the young Peregrines, two of which engaged the diminutive Taita, chasing it around a huge columnar bluff. The Taita eventually went into its eyrie, just 300 metres from that of the Peregrine.

In the course of many years spent surveying and monitoring falcon populations in Zimbabwe's Zambezi Valley, I have often been entranced by the acrobatic and exciting flight of Peregrines. Sadly, with the loss of large areas of woodland in the region due to the influx of subsistence farmers into the Valley, it seems that Lanner Falcons may well continue to expand their range there at the expense of Peregrines and Taitas.

PEREGRINE FALCONS IN AFRICA
Five races of Peregrine Falcons occur in Africa: the nominate European Peregrine Falco peregrinus peregrinus is a vagrant to the Mediterranean region of North Africa; the Siberian Peregrine F. p. calidus migrates to East and southern Africa during the southern summer; the Barbary Falcon F. p. pelegrinoides, a desert race of North Africa, sometimes extends as far south as northern Kenya; the Mediterranean Peregrine F. p. brookei is resident in northern Kenya; and the African Peregrine F. p. minor is a resident of Africa south of the Sahara.

The African race is one of the smallest of the 19 subspecies, with males weighing about 500 grams and females about 750 grams. Relatively little has been published on it, and its status has been largely misunderstood. Recent work in Zimbabwe, Namibia, South Africa and East Africa, however, shows that the Peregrine is not especially rare. With the encouragement of the Department of National Parks and Wild Life Management (DNPWM), and support from The Peregrine Fund Inc. (USA), the Zimbabwe Falconers' Club (ZFC) has taken the lead in researching the status and ecology of the Peregrine in its area. Its study includes examining the impact of pesticides, and it has pioneered the captive breeding and release of the African race, with more than 70 releases to date.

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