1 00:00:00,330 --> 00:00:05,640 Hello, my name's Lindsay Turnbull and I'm an associate professor in the Department of Plant Sciences 2 00:00:05,640 --> 00:00:10,740 at the University of Oxford, and we're right in the middle of this very serious corona virus crisis right 3 00:00:10,740 --> 00:00:15,810 now. And my students are all stuck at home and we want to keep them in touch with biology 4 00:00:15,810 --> 00:00:21,240 and keep in touch with us. And so we're going to make a new series of videos and they're going to be called back garden 5 00:00:21,240 --> 00:00:47,590 biology. 6 00:00:47,590 --> 00:00:52,750 So welcome to this episode of Back Garden Biology. Why were once again going to look at some birds 7 00:00:52,750 --> 00:00:57,780 at this time? The birds of choice are going to be pigeons. And I want to start with 8 00:00:57,780 --> 00:01:02,850 the wood pigeon of the wood pigeon is very common in Britain. There are an estimated five 9 00:01:02,850 --> 00:01:08,550 and a half million breeding pairs. So you're almost certainly see them in your garden. If you have a garden, 10 00:01:08,550 --> 00:01:14,190 unless you live right in the middle of a city where you might have another kind of pigeon, that will be coming to later. 11 00:01:14,190 --> 00:01:19,380 Now, the wood pigeon is a very familiar site. They can become quite tame if you feed birds 12 00:01:19,380 --> 00:01:24,540 in this feed around on the ground like this one. There's also some very 13 00:01:24,540 --> 00:01:30,390 familiar sounds associated with the wood pigeon. So the call of the wood pigeon is very distinctive. 14 00:01:30,390 --> 00:01:35,640 It sounds like someone complaining about their feet. That's how my uncle described it. Someone saying my poor feet 15 00:01:35,640 --> 00:01:49,530 but my poor feet. Here it is, in case you don't know what I'm talking about. 16 00:01:49,530 --> 00:01:54,550 The other very familiar sound of the wood pigeon is the clapping of the wings. So if 17 00:01:54,550 --> 00:02:02,430 you walk out into your garden and they're feeding somewhere, you might hear a noise like this 18 00:02:02,430 --> 00:02:07,450 and lots of pigeons make that kind of clapping noise as they take off. And it's something to do with 19 00:02:07,450 --> 00:02:14,270 him being able to generate a lot of lift because they're big birds. I mean, it's about a rocket off vertically. 20 00:02:14,270 --> 00:02:19,390 All right. So those are some of the familiar sounds and sights. This is a sound that you may be a bit less keen to 21 00:02:19,390 --> 00:02:25,080 hear in your garden. 22 00:02:25,080 --> 00:02:30,180 That is the sound of a wood pigeon attacking a lilac tree in my case, so 23 00:02:30,180 --> 00:02:35,580 they will often sit in the top of various trees in my garden and attack with foliage. So they're just eating 24 00:02:35,580 --> 00:02:40,950 the mature leaves of things like lilac and plum trees and hawthorn. And you think really 25 00:02:40,950 --> 00:02:46,530 those leaves are clearly not very nutritious as we have seen in the world is green episode leaves. 26 00:02:46,530 --> 00:02:51,720 Mature leaves are not energy dense food that poor quality food. So how 27 00:02:51,720 --> 00:02:57,180 can a large bird, a wood pigeon that weighs about as much of this bag of beans, about half a kilo 28 00:02:57,180 --> 00:03:02,490 or a standard bag of pasta? That's how much they weigh. How can they get away with eating such rubbish 29 00:03:02,490 --> 00:03:07,650 food? So we need to ask ourselves, how would Pageau, which is a big bird, 30 00:03:07,650 --> 00:03:12,870 can survive when it only eats low quality food? Now, that argument doesn't just apply 31 00:03:12,870 --> 00:03:17,940 to wood pigeons so that all people in the world who do not believe that animals like this ever 32 00:03:17,940 --> 00:03:24,030 really existed. Now, this is a model of a Brachiosaurus and that is a species of sauropod. 33 00:03:24,030 --> 00:03:29,400 And the sauropods were a type of dinosaur that were the largest land animals that have ever walked 34 00:03:29,400 --> 00:03:34,590 the earth. And they were truly gargantuan, some of them. And we know that they only at low quality 35 00:03:34,590 --> 00:03:39,720 food. They just browsed on the trees of the time. And some creationists have said, well, we don't 36 00:03:39,720 --> 00:03:45,030 believe they exist because it's impossible to imagine an animal that large could possibly have existed, 37 00:03:45,030 --> 00:03:50,040 if at all it was eating this low quality food. So how is that possible? Well, the truth is, if you think about 38 00:03:50,040 --> 00:03:55,110 mammals today, the very largest mammals, things like elephants and rhinos, also eat 39 00:03:55,110 --> 00:04:01,350 very low quality food. So it's a general pattern that we see. And actually it does make sense. 40 00:04:01,350 --> 00:04:07,020 So the cells inside large animals are actually much more efficient and require 41 00:04:07,020 --> 00:04:13,110 less energy than the cells inside a small animal. And that's something to do with scaling. 42 00:04:13,110 --> 00:04:18,300 It's masses. But it is true that small animals require much more food per 43 00:04:18,300 --> 00:04:23,370 unit mass than a large animal does. So actually, it's only large animals that 44 00:04:23,370 --> 00:04:28,500 can survive on low quality food. Small animals simply can't. So a shrew 45 00:04:28,500 --> 00:04:33,540 can die overnight if it gets stuck in a trap and it doesn't have food. There's no way that will happen to 46 00:04:33,540 --> 00:04:38,550 a large animal. So actually, it's one of the selective pressures for getting large. As you 47 00:04:38,550 --> 00:04:43,650 can then have access to all the plentiful, low quality plant food that's out 48 00:04:43,650 --> 00:04:48,960 there. So I've got this wonderful diagram drawn by former student Pandora Jun. 49 00:04:48,960 --> 00:04:54,390 And this is a pigeon. So the pigeon eat some food. It doesn't have any teeth to grind 50 00:04:54,390 --> 00:04:59,490 up the food first. And it goes down the oesophagus into the crop. And this is like a storage place 51 00:04:59,490 --> 00:05:04,650 where it can keep a lot of food that it eats rapidly. So it can then fly off and doesn't have to stay around 52 00:05:04,650 --> 00:05:10,020 on the ground for a long time. And from the crop, the food is passed into a first stomach. 53 00:05:10,020 --> 00:05:15,060 Has a horrible name. A proven track is to remember that. And that first stomach is a bit like our stomach 54 00:05:15,060 --> 00:05:20,130 in that it secretes hydrochloric acid. And a key enzyme to help digest food. But 55 00:05:20,130 --> 00:05:25,350 there's also a second stomach, and that's called the gizzard. And that's really muscular and 56 00:05:25,350 --> 00:05:30,360 strangely in pigeons. It contains a lot of gravel and grit and sand. The 57 00:05:30,360 --> 00:05:35,580 pigeon deliberately eats. And so the food is churned up here. And then it's often passed 58 00:05:35,580 --> 00:05:40,680 back into this stomach to get some more acid and enzymes and the fuegos backwards and forwards and backwards and forwards 59 00:05:40,680 --> 00:05:45,810 between these two stomachs until the food is ground up and digested. And then it can go 60 00:05:45,810 --> 00:05:50,820 down the long the short small intestine where the good stuff's all absorbed. Now, 61 00:05:50,820 --> 00:05:55,830 the problem. Okay, that's great for the pigeon. So it's able to digest and get nutrition 62 00:05:55,830 --> 00:06:01,020 out of this low quality food. But what about the nestlings, the young birds? They 63 00:06:01,020 --> 00:06:06,090 need proper food. They need lots of protein and lots of fat. And that's not going to come from this 64 00:06:06,090 --> 00:06:11,310 low quality diet. And so pigeons got a really special and cool adaptation for that. So when 65 00:06:11,310 --> 00:06:16,380 the chicks hatch, the adults stop feeding a couple of days beforehand, and then both parents 66 00:06:16,380 --> 00:06:21,390 can regurgitate from the crop a special food called crop milk. 67 00:06:21,390 --> 00:06:26,760 And it's basically sloughed off cells that are just full of protein and fat and they regurgitate those up. 68 00:06:26,760 --> 00:06:32,490 And that's all squabs, which is what the young birds are called get for the first week or so of life. 69 00:06:32,490 --> 00:06:37,680 And only after that to the adult birds start to feed a bit and start to give the young birds 70 00:06:37,680 --> 00:06:42,840 a bit of ground up, solid food as well. And pigeon chicks grow really fast because this 71 00:06:42,840 --> 00:06:47,880 crop meal is so nutritious. And it's also a reason why pigeons only ever 72 00:06:47,880 --> 00:06:53,400 have two eggs. They never lay more than that. And that's probably because they simply couldn't manage 73 00:06:53,400 --> 00:06:58,710 to provide that crop milk. So more than two chicks at a time. But they do have multiple 74 00:06:58,710 --> 00:07:03,900 brood. So it's quite different to the bloater who just mass warmth has a very large brood. They only 75 00:07:03,900 --> 00:07:09,180 have two chicks. But they can repeat breed all the way through the year and during 76 00:07:09,180 --> 00:07:14,460 lockdown. One of my former students, Anna Du'a, noticed that a pair of weapons were nesting 77 00:07:14,460 --> 00:07:19,470 in a tree just outside the window of her flat. And she managed to film them 78 00:07:19,470 --> 00:07:24,560 nesting and feeding the chicks through her not. As with our mobile phone, which is a really great 79 00:07:24,560 --> 00:07:29,840 achievement, and here we have a bit of footage, you can see the adults regurgitating that crop milk to 80 00:07:29,840 --> 00:07:35,000 the chicks and then the chicks growing and finally stumbling around, leaving the nest 81 00:07:35,000 --> 00:07:40,130 and they fleche successfully. Now what? Pigeons aren't the only kind of pigeon that you might see 82 00:07:40,130 --> 00:07:45,260 in your garden. And I'm going to go down to the town now, talks to town centre to me, another kind 83 00:07:45,260 --> 00:07:50,570 of pigeon that where even less well disposed towards. So I'm sitting in Bond 84 00:07:50,570 --> 00:07:55,640 Square in the centre of Oxford, just outside the Westgate. It's the shopping centre. 85 00:07:55,640 --> 00:08:00,860 It's all closed out. It's quite a lot of people down here. And the pigeons, of course, know this is somewhere 86 00:08:00,860 --> 00:08:06,050 where people congregate. So there's a big group of feral pigeons here. And what you're struck 87 00:08:06,050 --> 00:08:11,250 by is the diversity of them. They've got lots of different plumage, types and colours. And that's pretty 88 00:08:11,250 --> 00:08:17,030 unusual. If you imagine to be looking at a flock of sparrows, you wouldn't see that kind of diversity. 89 00:08:17,030 --> 00:08:23,030 I can also say that quite a lot of them have got rings on their legs. And I know them that my 90 00:08:23,030 --> 00:08:28,150 ex student, he was an undergraduates of mine. His name is Will Smith, who's now doing a P 91 00:08:28,150 --> 00:08:33,980 HD on feral pigeons and trying to understand their origins because they're all descended 92 00:08:33,980 --> 00:08:38,990 from a bird called the Rock Dive. And he's going to tell us a little bit more about 93 00:08:38,990 --> 00:08:44,060 feral pigeons and the rock star and what he's trying to do in a moment. But perhaps we can just pan out 94 00:08:44,060 --> 00:08:49,220 and see if we can see one of these birds. There were some just close by with some of these. But, yeah, 95 00:08:49,220 --> 00:08:54,410 it's quite interesting as well to see how people behave towards them. People sorts of love and hate them. 96 00:08:54,410 --> 00:08:59,480 People can't resist giving them food. But I've also seen a child sort of kicking at them, and that's a pretty common thing 97 00:08:59,480 --> 00:09:04,610 to see. When you think about it, it's quite odd because people generally are well disposed towards birds. 98 00:09:04,610 --> 00:09:09,960 And I don't think they would kick out any other kind of bird, but they seem to feel it's okay to kick pigeons 99 00:09:09,960 --> 00:09:15,020 or don't quite know what that's all about. Pigeons have 100 00:09:15,020 --> 00:09:20,240 been really valuable to scientists for a very long time. So, for example, Darwin was completely fascinated 101 00:09:20,240 --> 00:09:26,100 by other breeds of domestic pigeon and all of these were descended from a single type of bad could erupt. 102 00:09:26,100 --> 00:09:31,280 And these usually lived in caves near to the sea and they were probably really common. Dadge throughout Europe, Asia and North 103 00:09:31,280 --> 00:09:37,580 Africa. But nowadays we're way more familiar with the pigeons that we see in cities and towns. 104 00:09:37,580 --> 00:09:42,950 These city pigeons are called feral pigeons and they're basically free living. Domestic pigeons that have escaped 105 00:09:42,950 --> 00:09:48,170 and bred over the last few hundred years. They come in loads of different colours, but most 106 00:09:48,170 --> 00:09:54,350 of what's called a chicken pattern. And that means that they have lots of black marks on their wings, like this one here. 107 00:09:54,350 --> 00:09:59,360 So feral pigeons like this are really good at surviving not only in cities, but also in the same habitats 108 00:09:59,360 --> 00:10:04,550 as their ancestors. And when they meet rock doves, they tend to hybridised with them. 109 00:10:04,550 --> 00:10:09,740 And there are so many feral pigeons around that they can easily hybridised the rock doves completely out of existence 110 00:10:09,740 --> 00:10:14,780 and fully replace them. So this process is called extinction by hybridisation. 111 00:10:14,780 --> 00:10:19,940 And that's what I study. So Flamborough Head in Yorkshire was home to what was probably the last 112 00:10:19,940 --> 00:10:25,010 colony of rock in England. And it was also probably one of the largest Rogov colonies in Europe. And 113 00:10:25,010 --> 00:10:30,140 you can see why it's got massive cliffs with lots of open land above and lots of small caves 114 00:10:30,140 --> 00:10:35,320 opening to the sea. So it's perfect rucked of habitat for a pigeon spike to mix with rucked 115 00:10:35,320 --> 00:10:40,520 of that probably at the start of the last century. And if you visit today, there are thousands of feral pigeons 116 00:10:40,520 --> 00:10:45,830 and no rectums. And the same things happened across almost all of Europe. 117 00:10:45,830 --> 00:10:51,650 My research is looking at the extent to which rodef does still exist in anything close to a pure form, 118 00:10:51,650 --> 00:10:56,840 because the differences between Bodos and feral pigeons are quite small. We don't really know whether there are any colonies 119 00:10:56,840 --> 00:11:01,930 left that still represent the original form. We do know that there's a type of bed that 120 00:11:01,930 --> 00:11:07,130 seems to be a wild rodef, which is found in certain places in Scotland, in Ireland. And looking 121 00:11:07,130 --> 00:11:12,170 at plumage is sort of helpful in identifying it potential death. This is one 122 00:11:12,170 --> 00:11:17,840 that I caught in a flower meadow in the West. Now they are temporaries. He's got a big white patch on its back 123 00:11:17,840 --> 00:11:23,090 to blackbirds and its wings and then a general blue grey. However, 124 00:11:23,090 --> 00:11:29,060 there's lots of feral pigeons. Probably about a fifth of them have plumage that's almost identical to this. 125 00:11:29,060 --> 00:11:34,280 So another way of identifying more rodents is to study their morphology, their shape. 126 00:11:34,280 --> 00:11:39,390 In this photo, we have a feral pigeon on the left and a potential rubbed off on the right. 127 00:11:39,390 --> 00:11:44,870 So first of all, the set that's out see a and it's the white bit on the top with the beak 128 00:11:44,870 --> 00:11:50,720 is larger in the feral pigeon. Secondly, the beak is much thinner in the rock. 129 00:11:50,720 --> 00:11:56,270 As well as this, the orbital ring, which is the ring of skin surrounding the eye, is pale in the feral pigeon 130 00:11:56,270 --> 00:12:01,280 and dark grey interruptive. The biggest difference, once you get your eye in, is the shape of the head 131 00:12:01,280 --> 00:12:06,350 itself. If you look at the rough stuff has much more of a round full head than the feral 132 00:12:06,350 --> 00:12:12,110 pigeon. And that in the field, that's really distinctive. When you look at them through binoculars. 133 00:12:12,110 --> 00:12:17,220 Stuff like this can be really useful and explain what type of pigeon exists in a particular location. 134 00:12:17,220 --> 00:12:22,710 We really need to morphology image and genetics in combination to find out if there are any populations left. 135 00:12:22,710 --> 00:12:27,860 They're still a representative about death. So from my work, I get to go to the Hebrides and the Northern Ireland, 136 00:12:27,860 --> 00:12:33,170 Scotland. And I work with citizen scientists all around these regions to collect data to help us figure out 137 00:12:33,170 --> 00:12:38,190 where the poorest relatives are and where exactly feral pigeons are invading. So this 138 00:12:38,190 --> 00:12:43,430 work will allow us to protect any job of colonies, but also the process of exploring how the rodents 139 00:12:43,430 --> 00:12:48,950 gone extinct across its original range will give us a model system which is really useful in helping to understand 140 00:12:48,950 --> 00:12:54,020 how the process of genetic extinction works. And this is super useful because it's a process that affects 141 00:12:54,020 --> 00:13:00,860 lots of different species and it's a major contributing factor in the global US biodiversity. 142 00:13:00,860 --> 00:13:06,200 Well, we wish well every success with that project. What he's hoping is that on remote Scottish 143 00:13:06,200 --> 00:13:11,420 islands and possibly in remote parts of Ireland, there are populations of pure rock 144 00:13:11,420 --> 00:13:16,460 dive still left. And he has an army of volunteers out helping him. Thank you 145 00:13:16,460 --> 00:13:22,040 very much to all of them who are taking part with that important project. Why have 146 00:13:22,040 --> 00:13:27,740 feral pigeons ended up looking so different from their ancestors? Well, one of the reasons 147 00:13:27,740 --> 00:13:32,840 is that there was deliberate hybridisation. So people have been domesticating pigeons for around 148 00:13:32,840 --> 00:13:38,630 5000 years and possibly even longer. And as part of that process, 149 00:13:38,630 --> 00:13:43,970 they've also used some other species of pigeons, although they're derived from the rock dive. 150 00:13:43,970 --> 00:13:49,160 They've also been some crosses, for example, with the speckled pigeon, which is a North African species. 151 00:13:49,160 --> 00:13:54,440 Some of that chequered plumage has come in from that species. And in addition to that, pigeon 152 00:13:54,440 --> 00:14:00,290 fanciers who like to specialise in different breeds, different types of it's all the same species, 153 00:14:00,290 --> 00:14:05,430 but they concentrate on exaggerating particular features. And Pandora, Juhan 154 00:14:05,430 --> 00:14:10,580 and Joy, looking at all those different types of pigeon that exist out there, the different breeds. And she's 155 00:14:10,580 --> 00:14:16,250 drawn to some fantastic pictures as if they were kind of Tenzer profiles. So this is the frill back 156 00:14:16,250 --> 00:14:21,320 which has been bred to have these extraordinary curly feathers all over its back. And 157 00:14:21,320 --> 00:14:26,330 this one's called the pygmy poutre. And it's been bred to have an enormous sort of chest 158 00:14:26,330 --> 00:14:31,760 full of feathers. So it's an extraordinary shape. And if you type in fancy pigeon into Google, 159 00:14:31,760 --> 00:14:36,890 you will find some truly extraordinary pigeons. And through all that selective 160 00:14:36,890 --> 00:14:42,110 breeding, you know, pigeon fanciers have been able to produce an incredible array 161 00:14:42,110 --> 00:14:47,180 of different pigeons. Now, most of those are not going to be successful in feral flocks, which is why we don't 162 00:14:47,180 --> 00:14:54,110 see quite the same level of variation in the feral pigeons as we do in the fancy breeds. 163 00:14:54,110 --> 00:14:59,390 So perhaps it's time to re-examine our attitude to pigeons. It's absolutely clear 164 00:14:59,390 --> 00:15:04,850 that we humans are not very tolerant of the species that have actually been very successful 165 00:15:04,850 --> 00:15:09,950 in our wake. In other words, we're very sympathetic towards the species that we've kind of annihilated 166 00:15:09,950 --> 00:15:15,020 or were causing enormous problems for and are becoming rare as a result of our actions. But we're all 167 00:15:15,020 --> 00:15:20,360 the intolerance of the species that are actually doing very well and are able to take advantage of us. 168 00:15:20,360 --> 00:15:25,370 So, you know, rats, we talk about pigeons being rats with wings. And that's really unfair 169 00:15:25,370 --> 00:15:30,680 characterisation. They are just species that have been able to be successful around humans. 170 00:15:30,680 --> 00:15:35,810 And perhaps we should learn to tolerate them a little bit more. Mean, especially as a gardener. Pigeons don't 171 00:15:35,810 --> 00:15:40,970 really do a lot of damage in your garden. It's true of your growing brassicas and you definitely need 172 00:15:40,970 --> 00:15:46,550 to put a net over them. But otherwise they're relatively innocuous, really. 173 00:15:46,550 --> 00:15:51,680 So I would just urge you to think, you know, stop the pigeon. Never. Till next time. 174 00:15:51,680 --> 00:16:09,880 Goodbye.