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Peregrines are keeping it in the family...

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Paul Deane Paul Deane | 20:21 UK time, Wednesday, 6 June 2012

The Hawk and Owl Trust fitted a nest box in St John the Evangelist Catholic Church in Bath, and peregrine falcons have been nesting there since 2006. From March this year we've been following the intimate lives of this family. Genetic tests and close observation has revealed some extraordinary, rare behaviour.

In addition to the main breeding pair, we've observed a juvenile who is not only still begging for food from the father, but in return has appeared to pay his way by spending time incubating the pair's eggs, and more recently bringing food to the newly hatched chicks. Why has this young male not left to start a family of his own? And why should he be investing so much time caring for his parents' eggs?

What's more intriguing, is that genetic tests strongly suggest *(99.9% probability) that the mating pair are not just closely related - they are in fact mother and son. This son took charge after the disappearance of his father back in 2008, helping his Mum raise that year's chicks and since then they have mated each year. Is this normal behaviour? Is it viable? And is it a one-off or are there other cases of this in the avian world?

It's usually assumed that inbreeding increases the likelihood of recessive, deleterious genes being expressed. But can it ever have desirable effects?

Peregrine falcons have suffered a number of population crashes, for example as caused by use of DDT in the 1960s. These dramatically reduced the variety within the peregrine gene pool, making some inbreeding inevitable.

A study in 1999 on peregrine falcons in the midwestern United States investigated several cases of close inbreeding. They identified 4% of the population in which the adults were closely related (half siblings, full siblings or mother and son). The researchers also observed a very similar family situation as we're seeing in Bath. Interestingly, they did not record any indication of genetic problems in the offspring. All offspring were normal and breeding success seemed unaffected.

So is something happening here that doesn't result in the usual negative effects of inbreeding, not at least at the same rates as we see in other complex animals?

So returning to the juvenile helping his parents on St John the Evangelist Catholic Church in Bath, perhaps the reason that he hasn't left the parental nest is due to the lack of suitable nesting sites in the city - has the population recovered so much that it is hard for territorial peregrines to battle over prime property?

Moreover, could it actually be beneficial for our juvenile to invest his time in these 'half-siblings' as they actually share 75% of his genes. If he were to risk leaving this home-nest and starting a life on his, his offspring would only share 50% of his genes. Maybe he's worked out what is best for him!

All theories, particularly from geneticists, are welcomed!


  • Comment number 1.

    Hi, Just to tell you that during the Winter and early Spring I save my hair from when I wash it or cut it, then put it on twigs/branches in my trees or bushes in garden so that birds (usually Robins) can use it for their nests. from Katie

  • Comment number 2.

    I get the 75% genes theory that suggests reasons for the juvenile helping with the child-care. However, the comment above:"Maybe he's worked out what is best for him" points to the difficulty with this. How would he be able to know that the half-siblings in the nest were so closely related to him?!
    This would surely suggest a sixth-sense ability to detect the genetic make up of the chicks.

    Not saying this isn't possible but it opens more questions than it answers!

  • Comment number 3.

    In breeding drives to extremes most modern farm breeds are derived from inbreeding. This kind of family behaviour is quite common in a large range of animals, including some birds. It is perhaps surprising that unlike Lion prides and Elephant families etc. this hasn't received the attention of TV. https://www.thebeefsite.com/articles/755/inbreeding-in-cattle

  • Comment number 4.

    To answer Al question. He would not have worked it out but his actions promote the survival of the siblings, which likely also contain the same genes that cause the effect, so perpetuating the genes and the behaviour. The chick requires no more sense than to know who it's parents are, which is a product of it's up bring, as all it siblings will share 75%.

  • Comment number 5.

    I tried to let the Springwatch team know that I have read about other cases where a juvenile (previous offspring) have returned to help the parents rear their chicks. This has happened in Rome this year, and apparently in Montreal too. Read about Rome on this forum: https://www.peregrinefalcon-bcaw.net/viewtopic.php?p=176666

    I guess this sort of thing happens more than we realised.

  • Comment number 6.

    I am especially enjoying the fabulous footage of peregrines on springwatch, having recently "lost" my local peregrine. I work at Birmingham University, where a peregrine was nesting on our very tall clock tower - recently I noticed it was no longer flying around and I have since heard it was found dead, not sure if they know why - possibly stormy weather related? I really miss hearing its distinctive cry and seeing it from my office window - I was once lucky enough to see it swoop right past the building in pursuit of a pigeon! It was glorious. It has cheered me immensely to see into the nest at Bath and to hear that familiar sound again. :-)

  • Comment number 7.

    Hi, I have been trying to photograph local wildlife for a few months now but with little success, are there any tricks to doing this that I can do with a basic digital camera please? Also, how do I post pictures to this blog if that can be done please?

  • Comment number 8.

    Heres a short blog post and video of the Bath Peregrines! Camera used was only a £70 one and used through a scope! https://newton-st-loe-birding.blogspot.co.uk/2012/04/peregrine-falcon-falco-peregrinus.html

  • Comment number 9.

  • Comment number 10.

  • Comment number 11.

    It's "kin selection" that causes the juvenile peregrine to want to look after his siblings. The mechanisms are not a sixth sense as such, but kin recognition (the juvenile's ability to recognise that his siblings are closely related to him) and limited dispersal (there not being enough nest sites or mates available in the area for the juvenile to breed himself).

    Kin recognition may have been helped in this case by the fact he was begging for food from the breeding male (his father) earlier. The bond between the juvenile and his parents was still there and reinforced the juvenile's kin recognition.

  • Comment number 12.

    Iolo Williams said that if any of the juvenile peregrines come (fall) out of the nest on St John's , then the RSPB should be contacted. Rather than contact the RSPB, members of the public should contact the Hawk and Owl Trust as members of the Bath Group have dealt with incidences like this in previous years. Perhaps Iolo could issue a correction to his statement please?

  • Comment number 13.

    There are peregrines in central london, in the Barbican. They have been here about 6 years and often the chicks sit on our balcony as they are fledging.

  • Comment number 14.

    A lot has been said about these birds, which seems to be all positive!, no one seems either willing or prepared to comment on the devestating effects they have on the rest of the bird community.According to what we are told they must eat the equivelent of two blackbirds per day per bird, taking that, a breeding pair with two chicks say,must eat approximatly 6 blackbirds per day, 43 per week, 172 per month, wait for it a staggering 2064 per year. Now according to the RSPB stats there is 1400 breeding pairs in the UK, which calculates to 2,889,600 blackbirds per year. Along with the sparrow hawks,and other raptors who also take as many small birds as the peregrine, the RSPB should maybe look closer to home about the decline in the garden birds!!!!!!!!

  • Comment number 15.

    How did they ring the Peregrine chicks given the location of the nest?

  • Comment number 16.

    There are peregrines nesting, for the second year running, on the Lansdowne tower in Bournemouth too. I went to look at them last year, but all I could see from the street, over 20 minutes or so, was one of them ( presumably the male, judging by the Springwatch family's behaviour) sitting on the top of the tower doing not a lot. (Well, I daresay he'd describe it as pigeon-hunting :) )

    If the juvenile Bath male mated with his sister ( who shares 75 % of his genes) would their offspring have 87 1/2 % of their genes in common? And what if this inbreeding has been going on for generations? Couldn't it be the case that the mother and her FIRST mate were closely related too - daughter/father or siblings for instance? And her parents before her. This would mean that all subsequent percentages of shared genes in the later generations would also be higher.

    BTW, because of the curious and complex genetics of honey bees, all the workers are more closely related to each other and to any sister queens born of their mother queen than they would be to any offspring of their own (if they were capable of producing offspring). So it makes perfect Darwinian sense for them to devote their lives to nurturing and defending said siblings and the queen egg factory that produces them. I found it intriguing that our young male peregrine is actually in a similar position to theirs. But not exactly. He would be better off helping to rear his siblings than his own chicks by an unrelated female - if it was an either/or choice and the siblings wouldn't otherwise survive. (If there were enough food and territories then there would be more of his genetic material in years to come if he let his parents get on with producing 75 % similar siblings while he produced 50 % similar offspring each year.) With a shortage of territories and food his best bet of all might be to carry on as he's doing until such time as he can set up a nest with one of his 75% similar sisters.

  • Comment number 17.

    Lesley -

    Judging by what we saw in the program it's an artificial though open "nestbox" with a nice flap at the back for easy access to the chicks. The site was chosen by humans in the first place and so presumably accessibility for ringers (bird rather than bell), camera maintenance etc was one of the criteria. Most churches have stairs and ladders inside their towers and spires to allow access for maintenance work.

  • Comment number 18.

    Watching Thursdays program on the Peregrines when one of them almost got blown out of the nest box and what shocked me what was said next. If you do see a Peregrin out of it's nest let the RSPB know and they will put it back. Is this not interfering with nature as when the cat killed the Wood Warbler chicks and the Mink killed the kingfisher chicks but nothing was done to stop this and the Mink is not native of this country.

  • Comment number 19.

    Hello Springwatch Team, Love the programme,
    Saw the bit about peregrine falcons's peculiar breeding arrangement (mother-son). In Belgium, we've had a similar experience a few years back. There's a very nice website (to which I'm not related, but I visit it whenever I can) about falcons in Bruxelles and their lives (and their travels in UK-NL-DE). Pages are available in english and there are photos and videos and a live webcam. I searched the archives blog for you regarding this : visit this web page in english to read all about it ! (https://www.falconsforeveryone.be/nieuws_detail.jsp?lang=en&news_id=86).

    This page (https://www.falconsforeveryone.be/nieuws_detail.jsp?lang=en&news_id=117) is about falcons flying accross BE-UK-NL and is in english. You may contact them too, they might be interested to interact with you, who knows !
    Best regards.

  • Comment number 20.

    It would seem to me that the Peregrine Falcon has been given the 'Above all else' status. It is now a common bird visible in all parts of the Country and the predator-prey natural balance has swung definitely in favour of the Peregrine. The introduction and protection policies of the RSPB have led to a massive imbalance, it's all very well building up predator numbers to pre-war figures if the numbers of their natural prey have increased also, but this flawed policy is leading to decimation of most, if not all, other types of bird life. Unfortunately for Pigeon Fanciers the Peregrine's staple diet is racing pigeons, highlighted by the abundance of pigeon registration rings seen in the nest (quickly removed). Should pigeon fanciers retaliate this coming winter by confining their birds then the effect on local birdlife will be devastating. A flawed policy maintained bt the RSPB for the benefit of those who feel that there is something 'glorious' in watching birds being torn asunder and eaten alive.

  • Comment number 21.

    watching springwatch i think its a disgrace your taking the racing pigein rings out of the nest from one day to the next are they going the rings back to the rightfull owners of which many have paid a hard earned wage to pay for there beloved birds and having there rings back let them know what happend to there pigeon! are the rspb going to compensate the racing pigeon fancier for the loss of the birds. because they want to urbanise perigrins when they dont belong in city centres they belong in the countryside thats why the small bird population has gone down in urban areas because the rspb love birds of pray so much

  • Comment number 22.

    Sorry, but those comments about the peregrines decimating stocks of blackbirds, racing pigeons etc are rather naive and misguided. There are still only 1400 breeding pairs in the UK people - that's not very many! Before the age of raptor persecution it would have been much higher than this. For those who keep racing pigeons - this is hardly the natural order of things is it? The peregrines will do what they have evolved to do, and I'm afraid it's just bad luck if your specially bred captive birds are seen as an easy meal by a magnificent raptor who has a natural right to be here.

  • Comment number 23.

    @ 22 Adored99 - couldn't agree more. BoP will not hang around if there's nothing for them to hunt/eat, they will move on to an area that has a sustainable food source, allowing bird numbers to recover. It makes no ecological sense to decimate your food souce and then stay when you have the ability to move on - just like humans used to do before we became 'civilised'.

    The very fact they are nesting where they are shows that there is an abundance of food stocks for them. Racing pigeons are not their 'staple diet' and I will presume that your comment is based on being said pigeon fancier who has lost a bird(s) with perhaps the blame has been laid on the peregines? The peregine is still a 'natural' bird and not specifically bred to enhance certain traits.

    So in legalese - "objection - facts not in evidence."

    Much like the whole cat debate re small mammals and birds.

  • Comment number 24.

    David Riley - a peregrine blown out of its nest is a very different situation to the two incidents you mentioned, which both involve choosing one species over another. By putting the chick back you're not directly depriving a predator of a meal. No harm done.

  • Comment number 25.

    Sorry re above post - 2nd paragraph is to posts 20 and 21.

  • Comment number 26.

    Ther are many pairs of perigrines within a few miles of the church. Most of the quarries between Bath and Frome have pairs nesting in them. This is probably why the young peregrine has returned, as there are no available territories for him. It is an everyday occurence when travelling in this area to see these majestic birds hunting. I would question the number of breeding pairs that the rspb state, if this locality is anything to go by then it would be much higher. I think an earlier poster had a very valid point about the songbirds being taken. Peregrines take very few feral pigeons, as feral pigeons generally only fly in a short swoop from their perch and back again. This can be seen at St Johns church, there are feral pigeons nesting on the church, they are not afraid of the peregrine as they have learnt it cannot catch them. Peregrines take birds flying on a line of flight where they can swoop down or up onto them. The BTO state that a breeding pair of sparrowhawks need 3500 song birds per year to feed them and their young, I think that is rather more than two family cats would take in a year!

  • Comment number 27.

    A couple of the comments complaining about the peregrines show a woeful ignorance of ecology and a traditional attitude towards predators as being a negative thing. It's not peregrines upsetting the balance - it's disappearance of habitat plus man's interference. There was a study done in the UK showing the number of birds killed annually by cats and contrary to what country kate states, the number is far greater than one would imagine.

  • Comment number 28.

    I doubt that the young male realises that the two chicks have 75%, I'll be quite honest and tell you I am slightly confused as two the amount of genes in birds.I can not porduce a theory but I do think that it is good experience for the young male, he has alredy learnt that there is no point in bringing an entire pigion carcass into the nest. It may mean that he brings up his own broud better ( if he decides to move away from his parents ) because of prvious experience.

  • Comment number 29.

    Not a comment more of a question. We live on the Somerset Levels and have a pair of peregrines nesting in a tree fairly close to our house. It is possible to look down on the nest from a nearby hill and can see, we think, 2 chicks near to fledging. How common is it for Peregrines to nest in trees ~ we thought they preferred man made structures or cliffs?

  • Comment number 30.

    great article from bath.Over the last 18 months I’ve really got into these web cams of falcons as I have a nesting pair on the church 50 years from my house. They now have 3 chicks which should fledge next week (around 20 June) I can’t wait to see all five birds flying. Sadly not on the web but regular uploads by the church. https://www.youtube.com/user/allhallowsgedling
    My garden is regularly occupied by keen birdwatchers as I have a fantastic view of their antics. (Spring watch team welcome)

  • Comment number 31.

    reply to comment 27,i live in an area in Scotland unchanged habitat for at least 50 years as far as i am aware( probably more), and the only thing that has changed is as you correctly say is man's interference which now has these raptors protected by law!!!!, do you really believe that Cats are to blame for the demise of the garden bird population?, i have several cats in and around where i stay and have never seen one with a dead animal or bird, or heard of the owners saying that they bring them back to the house!! Some people are easily fooled by what they read, the people who work in this area ( game keepers, framers tell you the true story) these birds are causing havoc not just with garden birds, but game birds also. They need to be controlled!!!!


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