«THE PEREGRINE FALCON IN INNER LONDON AND FACTORS AFFECTING ITS EXISTENCE IN URBAN LONDON ——— DAVID JOHNSON Abstract Following the recovery of ...»
THE PEREGRINE FALCON IN INNER LONDON
AND FACTORS AFFECTING ITS EXISTENCE IN URBAN LONDON
Following the recovery of the Peregrine Falcon Falco peregrinus in south-east England
from the 1980s onwards, this species expanded its range westwards along the Thames
in the 1990s and it was only a matter of time before the Peregrine would breed in Inner London (the Inner London recording area of the LNHS). When I spoke to the late Derek Ratcliffe about Peregrines breeding in Central London he said, “They should flourish as they have all they need; tall buildings to nest on and a plentiful supply of food in the form of the Feral Pigeon.” Having been involved with Peregrine Falcons for over 30 years
- either flying or observing them - it was wonderful to see them in London in the late 1990s. This paper deals with the issues that arise for the Peregrine in the truly urban environment of Inner London from 2001-2014.
Breeding pairs The first pair of Peregrines to breed in the LNHS recording area (the ‘London Area’) was at Docklands in 1998. It was not long before a pair bred in Inner London at Battersea Adult male on his lookout perch at the Tate. (David Johnson) 190 LONDON BIRD REPORT NO. 79 Power Station, in 2001, where three young were successfully reared. Since that first breeding success Peregrines have gradually spread out, and in 2003 a second pair attempted to breed at a site near Regent’s Park. The eggs mysteriously disappeared that year, but in 2004 this pair successfully reared two young. It was intriguing to see that the off-duty bird liked perching on the tower of the Tate Modern, by the river, even though this was about three miles away. Territories in the early days were huge, as there were so few pairs that there was no competition for nest sites. In 2005, hopes for the Regent’s Park site were dashed when the birds did not return and there was no real indication as to where they might have gone. However, during a watch from the top of St Paul’s Cathedral, a Peregrine eventually appeared and was visible until it disappeared into a very promising looking crevice on a distant tall building.
Further investigation revealed that this was the chosen nest site and that the female had already laid two eggs on a flat, hard ledge. She soon deserted this site because the eggs rolled around so badly that she could not incubate them. Instead, she laid the remainder of the clutch on a pile of bailing rope and debris she found high up on a ledge on the Old Bailey. Incubation there went on for seven days until one of the birds’ talons got caught up in the ‘nest’ material and dragged it over the edge, where the eggs smashed. Incredibly, the very next day she was back at the Regent’s Park site, where she soon laid a second clutch and duly brought off three young, but this was the last year they bred at Regent’s Park. Since they seemed to prefer the Tate site, provision was made for the birds to make a proper scrape in the hope that they would breed successfully in 2006, and this is exactly what happened. The pair went on to rear 28 young in their 12 breeding seasons together from 2003 to 2014: a magnificent achievement.
Three years later a third pair occupied a site at Vauxhall and their first breeding success was in 2010, fledging four young. This pair spends the non-breeding season on the Houses of Parliament. A further pair became established at Charing Cross Hospital (Fulham) that year and they duly fledged three young in 2011. A pair was found breeding on the east side of the city in 2012 and a new pair bred in the west of the Inner London area in 2014, rearing three young. All these pairs have been faithful to their nest sites, which are becoming traditional.
At the time of writing there are seven pairs of Peregrines in Inner London, six breeding (as detailed above) and one non-breeding pair. These non-breeding birds are on territory in the western part of the area but have not yet found a nest site where, a) the owners want them on their building or b) ledges suitable for egg laying are available. Instead they
have laid on unsuitable surfaces such as window ledges and concrete paving slabs where there is not any material to make a shallow depression (scrape) to keep the eggs together.
If the eggs can roll around, the female cannot incubate them properly; she may incubate only one egg out of the three or four, and when there is a nest relief the male could, and does, incubate the ‘wrong’ egg, leaving the warm egg to go cold resulting in breeding failure.
In Inner London, Peregrines start incubation in March with the chicks fledging in early June. Juveniles disperse naturally, and there is no evidence of one being aggressively chased away. Occasionally a juvenile may still be hanging around in October/November but it will go before the next breeding season starts. The juveniles will usually disperse around August/beginning of September.
Sometimes individuals from one brood may drift into another pair’s territory and accidentally they can become adopted. When the juveniles become stronger and more confident on the wing, they fly further away from the nest site exploring the area around them. This is when they meet up with other exploring juvenile Peregrines and, as the juveniles all look the same, the adults of the territory they go to do not know that their family has increased. With the density of Peregrines in Inner London becoming greater and territories getting smaller, this will occur more often. This happened in June 2012 when the male juvenile from the Tate site went east and joined another family, and he occasionally came back to the Tate site with another juvenile Peregrine.
This will occur in June when the juveniles are fresh on the wing but, come July, new juveniles drifting into these areas will often get chased out of the territory by the resident juveniles who now see them as intruders.
Nest site complications The types of building in Inner London on which the Peregrines have chosen to breed are varied, and include power stations, office buildings, churches, hospitals and residential tower blocks. Experience has shown that, in order to ensure that the birds have a peaceful and successful breeding season, it is often essential to meet the owners of buildings, contractors, maintenance engineers and sometimes the Metropolitan Police Wildlife Crime Unit, to reach a clear understanding of what is needed.
As a Schedule 1 Species, the Peregrine is well protected by law, but when people in residential tower blocks are told that they cannot go near the nest site between January (when the breeding cycle begins) and the end of July (when the juveniles are strong on the wing) they are not easily persuaded to accept breeding birds on their building.
Generally, if maintenance work is done outside the breeding season - from August to January - it should give contractors sufficient time to do their work. Thanks to their co-operation, a lot of breeding attempts succeed which would otherwise fail.
Nest site suitability Given all the tall buildings in Inner London and the number of new ones planned, Peregrines should be able to find new sites in the future but their success will depend on various factors. It is essential that the birds are not encouraged on to unsuitable buildings, where they may attempt to breed but they will fail to fledge successfully.
Unfortunately, well-meaning people often suggest putting up Peregrine nesting boxes or trays on unsuitable buildings because of their desire to ‘give something back to nature’ and likewise building developers can misguidedly believe that this is a means of fulfilling a need to make provision for biodiversity on new constructions.
T H E P E R E G R I N E F A L C O N I N C E N T R A L L O N D O N 193This juvenile desperately clings to the side of the building. (Phil Wallace) Particularly important is whether there will be enough (or any) perches and landing places for the young when they fledge. The current practice of facing new tall buildings with glass means they do not provide any potential landing ledges. All may be well until the juveniles make their first flight when after typically flying 60-70 metres from the security of the nest site they realise that they are going away from all they know. They then turn back only to find that they have lost height and - with no ledge to give them refuge - they will crash land and be at the mercy of cars, foxes or people (some of whom may have the best of intentions but will pass the bird into the wrong hands).
When the building is made of brick or concrete a young bird can sometimes cling to it wondering what to do. As they have not yet learnt that their tail is designed for braking, turning or slowing down, they usually hit the building quite hard. If they survive - and some do not, especially if it is a glass building - they slide down and usually end up on the ground.
If an urban nest site can be carefully monitored at the critical fledging time, a fallen juvenile can be placed on a tall roof near by or perhaps even on the nest site roof. It will take this particular bird a day or two to get over the shock and try again. Usually this ‘cooling off period’ seems to do the trick, because when it makes a second attempt its flight will be more powerful, longer and with quicker wing beats. Such birds seem to have learnt very quickly to stay up high and instead of panicking, as they do on their first flight, they think about where they are going and try to land properly. After three days their landings are reasonably good as they have learned how to use their tails for stalling before landing. Occasionally they get over-confident and overshoot a landing perch but then they simply fly around and land normally somewhere else. These problems are more serious for urban Peregrines than for those that breed at the more traditional cliff sites, where the young birds can more easily find perching places on 194 LONDON BIRD REPORT NO. 79
Juveniles ready to fledge: three males and one female. (Tony Duckett)
rocks, gorse, bracken etc, and learn to scramble and flap their way upwards until they find a secure perch.
Traditional stone-built churches have the potential to be some of the best nest sites for urban Peregrines in the future, providing they are high enough. This is because they can offer a well-protected nest site with lots of perches for the juveniles and they usually have the advantage of not being subject to the normal disturbances of modern life (eg window-cleaning, and lift- and aerial-maintenance).
Size of territory Originally the size of a Peregrine’s territory in Inner London was between five and eight square kilometres (two and three square miles). With the number of tall structures to nest on and the abundant food supply (primarily the Feral Pigeon) these territories will get smaller with the increasing density of the population. At the moment, there are already two pairs which nest just under 1.5 kilometres (1 mile) from each other and both pairs have bred successfully in the same year. In Inner London, especially north of the river Thames, there is room for further pairs of Peregrines to establish territories.
Intruders The number of Peregrines in Inner London is increasing, and this can be seen by the number of Peregrine ‘intruders’ that fly into occupied territories in February, March and April. There appears to be a very healthy reservoir of Peregrines waiting to take over when an opportunity arises, and serious aggression can sometimes occur. In 2013, for example, the Tate pair chased an intruding male into a building where he became stuck.
He was rescued, taken to a vet and released the following day. At another site, in March 2014, an adult male got caught in pigeon netting whilst being chased and had to be taken to a wildlife hospital. Within 24 hours a new male took his place and was soon soaring above the nest site with the adult female.
T H E P E R E G R I N E F A L C O N I N C E N T R A L L O N D O N 195Conflicts with other species Several large raptor species regularly fly over Inner London and can come into conflict with the Peregrines. Common Buzzards and Red Kites, both of which are increasing in number in southern England, regularly have to be chased off. If these birds go over very high, the Peregrines do not see them as a threat and just watch them drift over. If they are too low, the adult Peregrines fly up to meet them from their ‘lookout perch’ and really go into the attack. Sometimes the large raptors will roll over on their backs and present their talons to the Peregrines; but after a few minutes of being persistently dived at, these raptors move on very quickly.
Other species that are frequently chased away are Grey Heron, Carrion Crow, Herring and Lesser Black-backed Gull. The Carrion Crow is one bird which Peregrines particularly dislike, and the falcons will aggressively chase each Crow until they have all dispersed.
The one species above all which Peregrines are determined to keep out of their territory is the Harris Hawk. In the author’s experience, this is the only intruder that the Peregrine will kill or be killed itself in the attempt. Harris Hawks are being flown on a regular commercial basis by pest-control companies to scare away Feral Pigeons.
When the Peregrine sees such a hawk, it immediately starts calling and diving at it. One was seen dropping like a stone after being hit by a stooping Peregrine, and a working Harris Hawk was given ‘early retirement’ when smashed in the wing by a Peregrine. In 2012, a Harris Hawk which was being flown by its handler near St Paul’s Cathedral was attacked so relentlessly by the Tate pair that it was some hours before it would leave the sanctuary of its tree and return to its handler. With the increasing density of breeding Peregrines in Inner London, there is more risk of nesting pairs being disturbed by pest-controllers’ birds, especially during the breeding period when the young have recently fledged and are still vulnerable and dependent on the adults.