Peregrines
in a Devon Quarry
A DIARY OF THEIR BREEDING IN 2015
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PE REGR I NE S I N A D EV O N QUA R RY, A D IA RY O F T H E IR BRE E DI NG I N 2 0 1 5
Male Peregrine, known as a “tercel” Peregrine Falcons are an iconic, mag-mystical bird, revered and adPeregrine Falcons are an iconic, magnificent almost nificent almost mystical bird, revered mired as the epitome of natural evolution. In the same way that lions and selection admired as theand epitome of natuselection and evolution. In thea Peregrine Falcon, at the top of and tigers are admired as theralapex predator, then the food chain, is equal in status. For the last few years I have been fortunate enough to have permission from the land owner, to photograph and observe at a peregrine nest site, deep in the heart of Devon, UK. In addition, I am licensed by Natural England to photograph at this site. Peregrine Falcons are a specially protected bird in the UK and it would be an offence to be at a nest site without the necessary licence. Sadly, even though they are now a much more successful bird in England and faring reasonably well, they are still the subject of persecution and cases of poisoning and shooting are still far too common.
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Introduction. Tercel
The Peregrine Falcon (Falco peregrines) is now a much more common bird in the UK than it was 50 years ago and is a success story that needs to be told. Worldwide, there are 16 sub species and they can be found on every continent apart from Antarctica. They have proved to be an adaptable species here in the UK and many cities, including Bath, Norwich, Sheffield, Nottingham, Derby and Exeter have breeding Peregrines on their cathedrals and churches. The collapse of the UK population of Peregrines in the 1960’s has been well documented and the banning of organochlorine pesticides, along with far less persecution, has enabled populations to climb to more than 1500 breeding pairs nationwide. Peregrines are sexually dimorphic with females up to a third larger than males. They are roughly the size of a Carrion Crow, females on average weigh around 1.1 kg and the much smaller male around 670 g. As a bird of prey they are an obligate carnivore and almost all of their prey is made up of birds which they catch on the wing with rapid flight and agility. They live up to a maximum of 15 years but with an average lifespan of around 6 years. 2
Peregrines pair for life but will choose a new partner with the demise of a mate. Breeding age is acquired in the second year and pairs in the UK will remain close to their nest territory throughout the year. Juveniles, once independent will disburse to find territories of their own but apart from that, in the UK they are none migratory. There is evidence that the UK population is swelled in the winter by some birds from Northern Europe. Breeding activity commences in early spring. Historically, sea cliffs, and craggy outcrops on moorland and montane, constituted an appropriate nest territory but in recent years coinciding with their recovery since the 1960’s - a new urban environment has proven to be more than adequate. Cathederals and churches with artificial nest ledges have become very attractive and some, such as St Davids Church in Exeter, Devon has had Peregrines breeding there for the last 18 years. The first eggs appear in the nest around the last week of March or beginning of April - around the spring equinox. Incubation lasts for between 29 to 31 days. The young chicks fledge the nest at around 42 days, a total of approximately 80 days between the first egg and the fledging of juveniles. Juvenile tercel.
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One does not need to study a Peregrine for long to become awestruck by the  power and efficiency of their hunting prowess. But, hunting skills aside, both their sleek shape and smart, immaculate plumage makes them a bird of utter beauty and to me, they have no equal.  They have eyesight eighteen times more efficient than a human and the ability to fly at speeds faster than any other animal on the planet, only adds to their magical appeal.
Female Peregrine feeding chicks from a Magpie kill.
Prey selection. Evolution has dictated that there is no place for anything other than the most efficient and successful individual. Prey is chiefly birds which can vary in size from the tiniest Wren (Troglodytes troglodytes) to larger species, even ducks. Prey selection will vary depending on the location of territory. Sea cliff nesting birds will obviously predate shore birds and waders, whereas urban nesting birds will capture feral pigeons and other species found in that environment. 4
Tiercel flies to the nest ledge At my study site, an unused quarry ringed by woodland, I have visually recorded at least 16 different prey species being brought to the nest ledge.
This has included
Robin, Bullfinch, House Martin and Swallow as well as Blackbird, Starling and Song Thrush. Possibly because it is a species easy to identify , in 2014, I counted 15 Greatspotted Woodpecker (Dendrocopos major) and all caught by the male. The choice of prey by each parent has been interesting and notable. The largest prey that I have seen the male bring has been a Great-spotted Woodpecker, whereas the smallest prey brought by the female has been a Collared Dove. This would indicate to me that the two sexes are choosing prey, dependent on their own body size. The predation of Great-spotted Woodpecker is particularly remarkable. With the nest ledge close to a woodland habitat it suggests several factors. Firstly, the abundance of woodpeckers at the location and secondly the striking, noticeable plumage and flight pattern of the species and possibly the ease that they can be seen and caught. It could also point to a learned preference for this species by the male. Prey selection is a study in it’s own right, for example the Peregrines nesting on St David’s Church, Exeter, Devon have been studied since 1998. In that time well over 100 different species have been identified. 5
Woodpeckers have a relatively slow and undulating flight pattern and are quite common in the woodland adjoining the territory. This may account for the regularity of them as prey. It is quite unusual to see the tercel with this woodpecker (see below), complete with the head intact. The head is usually removed either intentionally or when the spinal chord is severed. It is curious to see in the picture and the one on the next page that both birds are in the same tree which is close to the nest ledge. It’s always very riveting when you know that a Peregrine has a kill, every day will be different and the anticipation and then discovery of prey species is very engrossing. Watching the falcon dealing with a large prey item is compelling. Oddly, wing feathers and tails are removed before the remaining feathers are ripped out. There doesn’t seem to be too much effort to remove every feather and quite often there will be enough remaining to allow for identification.
Adult tercel with a Great- spotted Woodpecker kill.
Preening is vitally important.
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Great - spotted Woodpecker Prey items in the 2014 breeding season. Great - spotted Woodpecker Jackdaw Magpie Ferrel Pigeon Collared Dove Bullfinch Pied Flycatcher Barn Swallow Pied Wagtail House Martin Starling Blackbird Song Thrush
Barn Swallow
Robin 7
With smaller passerines, even with a close view it will be impossible to identify the species when just the legs and down remain. In this picture the falcon has caught a Jackdaw (Corvus monedula) and is in the process of removing the wings. You can see, if you look carefully that the head has already been removed. Prey is sighted from either a high perch but mostly by circling above. Once a target is selected the bird will “stoop” from height, folding the wings in to the body as it dives. Stories of the speed of flight are perhaps apocryphal but high speeds are achieved and thought to be over 200 mph. When in this dive, Peregrines are thought to achieve the fastest speed of any other living creature on earth. Quarry is hit at high speed with clenched talons and this will usually be fatal at the point of impact. As the prey tumbles unconscious, the Peregrine will turn in the air to grab the kill. Peregrines have a specially adapted hook on the beak - the tomial tooth - evolved to severe the spinal cord of their prey. Adult falcon with Jackdaw prey.
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Prey selection is of particular interest and like I have alluded to, it can be difficult and frustrating to identify the species, particularly small passerines. By closely studying this image I was able to identify it as a Barn Swallow (Hirundo rustica). It was brought to the 5 day old chicks. A fascinating choice of prey, it says so much about the agility of flight by the tercel who caught this bird on the wing of course. You can just discern the sickle shaped wings of the Swallow and the distinctive blue green hues on the back as well as a hint of white on the tail. During the 2014 season several Swallows were brought to the nest as well as the closely related and equally agile House Martin (Delichon urbicum). 9
A Magpie (Pica pica) is delivered to the nest ledge.
Magpie (Pica pica) is a regular prey choice by the falcon at this site. I would suspect that they are easily sighted and not particularly fast flying and relatively abundant. Interestingly, the falcon misjudged her landing in the video above causing much excitement from the vociferous chicks. The kill has been plucked and beheaded away from the nest. 10
A tercel hunting in the territory in 2014.
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The nest ledge. The nest, specifically at this site is typical and consists of a hollowed scrape in the earth with no nest material or lining. Â It is positioned high on a ledge, in an ancient quarry. Around the ledge there is a combination of bare rock and earth with a few plants such as naval wort, gorse and bracken. An overhang gives some protection from the worst of the elements. The talons and then body are used to form a crude hollow in much the same way as a domestic fowl would dust bathe in dry earth. Â There is a respectful relationship between the two adults because of size. Larger by almost a third in weight, the female is dominant over the male, she could easily kill him if the mood took her! However, in spite of this, there is a strong pair bond and pairs will stay together for life, or until the demise of one of the partners.
Both adults at the nest ledge.
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Separating by sex and age. Adult falcon
There are three plumage types to compare; female, male and juvenile. Firstly, the female (above and page 13.) Female Peregrines are referred to as a “falcon” and the male as the “tercel or tiercel.” These words are derived from the art of falconry. The word tercel perhaps points to the size difference between the two sexes, males can be up to a third smaller than a female. Others suggest that the origin may derive from the incidence of males in the clutch, often 2 females to 1 male! 13
Adult falcon
For the purposes of the book, from now on the birds will be referred to as “tercels” and “falcons”.
Not only is the “falcon” a larger bird, it has a relatively smaller head and is less distinctly marked on the face. The bare skin around the eye, see above, is larger and not as neat. The falcon is altogether, longer in the body and not as compact and dapper as the male. The colour on the back has more brownish hues than the tercel which is more slate blue, however, light can play a large part in how this manifests itself. Because of body size, the talons of males appear relatively larger. 14
Adult tercel.
This is the tercel, (see also next page.)
Notice the smarter head and neater bare skin
around the eye. The malar stripe (the moustache) is much more defined in the male and the breast, being snow-white, with very fine ticks on each feather, this is very noticeable from a distance Note the more blueish slate colour in the tercel rather than charcoal in the falcon. In the height of breeding condition, as both of these birds are, the talons are more yellow in the tercel whereas, orange/yellow in the falcon. Both sexes have barring on the body and underwing but the breast and throat is mainly just white but less strikingly so in the falcon. Feathers cover the legs almost down to the feet, these are heavily barred in the falcon but less so in the tercel.
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Adult tercel.
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Juvenile falcon
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Juvenile tercel.
Juvenile Peregrines have brown plumage rather than slate blue, there is a malar stripe and white is replaced by buff. Talons are yellow but the bare skin around the eye and the cere above the beak is bluish rather than yellow. The tail has a broad buff band at the tip and 5 to 6 dark bars on each tail feather. Every individual feather on the back is edged with a hint of buff. The wing feathers - primaries, secondaries and tercials are also edged with buff. The throat, breast and flanks are heavily streaked, unlike the adult plumage which is barred. There is a variable light patch on the back of the head. The wings almost extend to the end of the tail. At this age they are nowhere near as observant or cautious as adult birds and it’s easier to get a good photograph. In the picture, this young bird at around 7 weeks old - still not independent - has a kill, a small passerine delivered by the tercel.
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Juvenile tercel at around 60 days.
After juvenile birds have fledged the nest ledge they stay close by and wait to be fed by their parents.
In this video a youngster sits waiting for it’s parents to deliver
prey. Juveniles are dependent on their parents for weeks after leaving the nest. The first winter is a precarious time for all young peregrines and mortality in the first year can be as high as 70%.
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Juvenile falcon
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About breeding.
A clutch of eggs and a typical nest scrape. Courtship takes place for several weeks, even months, prior to egg laying. This can take the form of bowing to each other on the nest ledge or a nearby favourite perch. Mating is precarious and when it occurs, the male will clench his talons so as not to pierce the back of the female as copulation takes place. Eggs are a dark terracotta red with small darker dots. The laying of the first egg seems to coincide roughly with the spring equinox in this part of the world. Eggs are laid 48 hours apart. Interestingly, parrot-like birds also produce eggs every 48 hours and falcons are thought to be more related to parrots than they are to other birds of prey such as hawks and eagles. Incubation will commence after the second or third egg is laid. This is called asynchronous incubation and it ensures that not all eggs will hatch on the same date.
The older and stronger chicks in the clutch have an advantage over their
younger and smaller sibling, or siblings. 21
When conditions are perfect and prey is abundant, all chicks may survive but in times of hardship, the younger chicks will perish. In the event of the failure of one of the first laid eggs, the later eggs in the clutch will act as insurance. Incubation is between 29 and 32 days and is mostly undertaken by the female but the male will take over for short periods to enable the female to rest and feed, almost without exception, the female will incubate overnight. From the moment they hatch as nidicolous , altricial chicks they are fed by the adults on tiny pieces of meat, plucked from a carcass. The young white downy chicks, usually 3 but sometimes 4 , develop rapidly and it is easy to see the age difference, however as they progress the difference in size between the sexes becomes quite apparent.
The tiercel broods a newly hatched chick. The chicks are fed in a very gentle, attentive manner with no aggressive competition or sibling rivalry. In fact, quite the reverse. There is a pecking order, the older stronger chicks are fed first, quite often one at a time but not always. My observations seem to indicate that only when the older chicks have been satisfied will the younger and smaller bird move forward to feed and be fed with as much care and enthusiasm as the older chicks. 22
The newly hatched chicks are covered with white fluffy down. They are brooded by the parents, usually the female but the male will, from time to time, take over for short periods. For the first 6 days or so, the adult will sit tightly but after the growth of thicker down at around a week, the falcon will leave them un-brooded for increasingly extended periods. On hatching, they are silent, or perhaps more accurately, their begging noises, associated with being fed are too quiet to be heard. The calls become louder and more persistent as they become older, larger and more strong. Food at this stage is mostly brought by the tiercel and delivered to the falcon on the nest who will continue to pluck the kill and then delicately feed the chicks. She will eat pieces herself during this process. Almost without exception at this age, once the chicks are satiated she will depart the nest ledge with what is left of the kill and feed from it herself, usually out of sight. The tiercel will brood the chicks during this short period or they will be left un-brooded when they are slightly older. Food is delivered to the nest every three to four hours but sometimes I have been surprised at how long it can be between feeds.
A newly hatched chick. 23
For the first 20 days or so, the tercel will deliver most of the food but when the chicks are older and larger, the falcon will leave the nest to hunt for food which she will then bring to the ledge. Usually, the prey is brought straight to the nest and the falcon will take the kill from her mate.  Once delivered, the tiercel will depart  quite hastily. Their is a degree of aggression from the larger falcon and instinct dictates that the falcon seeks to protect her young, even from her own mate. On other occasions, the tiercel will bring prey and "prepare" it away from the nest, the falcon will then leave the nest ledge to take the kill from her mate and then bring it to the nest herself. As the youngsters grow and are on the ledge unbrooded, the tiercel will fly in with prey and feed the chicks himself. On other occasions he will deliver prey and depart to leave the chicks to feed themselves. However, the falcon will invariably feed the chicks, even when they are large and about to fledge.Â
A chick at 2 days old with a yet to hatch egg visible.
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Chicks are fed very delicately by the adults. In this picture they are 10 days old and the nest is already starting to get messy with the remains of previous kills littered around. This is useful for the observer because it enables identification of prey, the feathers in the foreground are from a Magpie (Pica pica) but it is impossible to name the kill that is being fed. The chicks, apart from being vociferous and excited when a kill is delivered, wait patiently in turn to be fed and do not squabble. As well as meat and viscera, the chicks will also swallow feathers. The adults will also feed from the kill as they feed the young, particularly if a morsel is too large for the chicks to take. 26
As they progress, their growth is rapid and there is a clear difference in size between chicks 48 hours older than their younger sibling. This size difference is exacerbated if the younger chick happens to be a tercel. True feathers will start to emerge at around 15 days and by this time the nest ledge is a noisy place, particularly when food is delivered. However, the lack of competition is remarkable. In the days prior to fledging, when the chicks are around 42 days old, I have witnessed nestlings guarding prey by crouching over the kill and covering it with open wings. At this stage, food is often delivered to the nest by the falcon and left unprepared and the youngsters will begin to learn how to pluck it. Prior to fledging, the youngsters practice wing flapping with small jumps and hops on the nest ledge. By this time, most of the white down, which still pokes through the plumage, has either fallen out or been removed during preening and I have seen youngsters removing this down themselves, deliberately with the beak. A few wisps may remain here and there on the back of the head even after the first flight. Many actions of an adult bird are seen in these youngsters such as preening - which they do from a very young age , even before they have feathered up - wing stretching and scratching.
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The talons are large and yellow even at hatching with strong, sharp black claws. Many bird species rest on one leg and this includes peregrines, however, it has been amusing from time to time to see juveniles lose their balance and stumble when first practising this skill. They will spend a considerable amount of time laid on their bellies, as if to take the weight of their legs. After 6 weeks, the nest ledge is a fetid place with copious white guano all around, splattered up the sides of the rock face adjacent to the ledge and over the edge to rocks and foliage below. There are remains of carcasses, various wings and tail feathers, passerine legs and leg bones. The young peregrines are very inquisitive and they peck at the flies and remains of various kills. From time to time they will come across a wing or leg with some meat still remaining. The chicks are extremely noisy when being fed, and the adults scream as they deliver food. It seems odd that the birds make no attempt to hide the nest ledge or its contents at this stage.
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Once fledged, young birds remain in the vicinity of the nest ledge waiting to be fed. At this time in their lives they are incredibly vociferous and will scream at the first sight of an adult in the hope that they will be fed.
They seem to be ready to eat
whenever food is offered. Here, the falcon brings a Collared Dove to a recently fledged juvenile. Mortality in the first winter is as high as 70%. But once they reach adulthood, they may live for as long as 15 years. They will not start to breed until their second or third year. This photo allows comparison between an adult and a juvenile. Note the bare skin around the eye and above the beak, yellow in an adult and blue-ish in the juvenile.
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nest failure.
In the breeding season peregrines can be quite vocal.
pic
This marked the end of breeding in 2015.
THE DIARY 2016
8th March - A Peregrine on the nest ledge. On this day last year I had recorded that I was uncertain if breeding was going to occur here that year, I had so much to learn about behaviour and still do. I had no idea if what I was observing then was normal behaviour or not. The birds went on to produce a clutch of eggs - eventually predated however - so it wasn't too concerning that for ages there was no sight or sounds of a peregrine. Experience has shown me that peregrines sit for hours quietly on a perch and I assumed that was the case. I have only visited twice this season and I have seen peregrines in the quarry on both of those visits, however, not together and I can't be 100% certain that there is a pair resident. But on my first visit last Friday I had been reasonably confident that I heard 2 different birds calling. I remained watching and waiting from the main hide for an hour or so and then made my way up and around the quarry to the tree hide. I was extremely careful not to disturb any birds that may have been in the quarry. Another long wait in the tree hide was unsuccessful and I then made my way back to the main hide just to check before I departed. Again I was very careful not to disturb any birds present and skirted well away from the edge of the quarry before then crawling in to the back of the hide. I scanned the quarry face hoping but not really expecting to see a bird even though I had heard a few calls while in the tree hide. There was no sign of a bird on any of the rocky outcrops that are favourite perches. I didn't expect what I saw next - on the nest ledge, there was a peregrine, it was sat in a nest scrape. I don't know how long it had been there but it remained sat and was still there when I left an hour later. I wasn't certain if it was a Tercel or Falcon. This is a good start to the 2016 breeding season and I am confident that I will be able to record breeding behavior again this year. One of the first things that I need to do is to establish if there is a pair of birds present and then try to identify them by comparing images taken last year. The tercel seen on the 4th, appeared to be quite distinctive and a different bird than the breeding tercel from last year. This years bird has a different shaped head and the markings on the face are not similar. On the back of the neck I noticed one brown feather. My feeling is that this is the young male seen in the territory last year after the disappearance of tercel 1 in April. My theory is that last year’s breeding attempt failed because of the lack of experience of the falcon, the demise of the tercel and then the immaturity of the replacement tercel.