Hello. Today I’m joined by Dr Stuart Sharp, from Lancaster Environment Centre. And Stuart is an expert on avian ecology. So perhaps the first thing would be to explain what ecology is and how it pertains to bird populations. Certainly. Ecology really is the study of organisms and how they interact with each other, and with their environment. So I’m a bird ecologist, first and foremost. And to really understand the biology of the birds, the ecology of the birds in question, then I really need to understand how they interact with other animals, plants, parasites, and indeed their environment, their habitat, the climate. And it’s all those processes combined, that we think of when we think of ecology.
And when you say parasites, that would include things like virus diseases, like flu as well, would be part of the ecology environment for birds? Absolutely. Right away from blood parasites, feather parasites, might be virus, bacteria. Everything that the animal interacts with in any kind of way. So why would birds seem to us often to be very vigorous and healthy flying around and making a lot of noise and so on? But do they have a large burden of disease? It obviously varies a lot from species to species. And you get outbreaks, just as you do in humans. Lots of wild birds are carrying things that are probably reducing their breeding success and survival a little bit.
But to our eye, until we actually capture the bird and look at what’s in their blood or in their digestive tract, we often can’t tell by looking at the condition of the bird. And that’s often the case as well with influenza in birds, with bird flu. Many of the varieties are what we call low pathogenic avian influenza or LPAI So they don’t produce a great deal of morbidity or mortality in the birds. And we don’t really know until we test that the birds are carrying them. That’s absolutely right. And I’ve had colleagues in the past who work on avian malaria. It’s the same principle.
Until they actually look at the blood in the lab, then it’s impossible to tell that that bird is carrying that disease. Lancaster University is a campus university, which means we’re out in the country to a certain extent. Just south of the town of Lancaster. And we have a lake here, Lake Carter, which has many bird species on it, if you’re lucky enough to see them. But Lake Carter is actually an artificial lake that was constructed about a hundred years ago by the former owners of the site for their recreational purposes. So how do artificial lakeland environments like Lake Carter or large park ponds in cities differ from genuine wetland environments? They have a lower diversity.
Lake Carter is quite typical, really you have a kind of suburban pond. A lot depends on the structure of the surrounding vegetation and how deep the water is in different places. Lake Carter is a classic suburban type pond where you would expect things like coot and mallard, which are quite generalist, can breed in most open water environments. And certainly this morning, both there’s plenty of mallard and coot around at the moment. So it’s quite a complicated situation we have. We have some species that use the British Isles as their summer ground and have other places that they go for the winter, prefer a warmer place for the winter.
But conversely, there are species that are coming in from colder, wetter areas to the northeast in Scandinavia and Siberia. And they were using the British Isles as a wintering ground, and then go back to colder places. That’s right. I think when many people think about migration, they might think of something like swallow or lots of our summer birds that feed on insects. They’re here in the summer months when you’ve got long daylight hours, and there’s lots of insect food around. And those species, generally speaking, winter in southern Europe or Africa. But as you say, come the wintertime, we also have migrants that bred elsewhere. We don’t have so many song birds that fit that category.
Although there are fruit-eating species like thrushes that move south that obviously struggle to find food in somewhere like Arctic, Sweden, or Norway in the winter. But really, I guess that the classic winter migrants would be the waterfowl. Ducks, geese, and swans, who have to move south because they live on open water. Their breeding grounds are open water, which is, of course, frozen. Yes, of course. And parts of northeastern Europe will be very cold, indeed. So is the migration pattern predictable on a species level? So some species will have some wintering grounds and some preferred summer grounds?
And is it predictable in the level of individual birds, or are individual birds very habit forming, or will they vary where they go from year to year ? That’s a very interesting question. And like lots of these things, the harder we look, the more complicated we realise that things are. If you think about it in the broad scale first of all, it’s certainly true that for many species, we can make good predictions about where birds that have bred in a particular area are going to spend the winter. And in lots of cases we’ve got a pretty good idea of the route that they take as well. However, there are lots of sources of variation.
Firstly for some species, the climate in a particular winter might dictate how many birds go, or how far they go. So thinking back to the waterfowl for example, birds that are breeding in areas that don’t freeze in one winter might not make that journey. Secondly, things do change over time. So earlier in the year I was teaching a Lancaster University field course in southern Spain where we spent a lot of time in one of Europe’s great wetlands, Donana National Park. And there were a lot of swallows around. This was in March, and I was speaking to the locals. And they were saying that those swallows had actually been there throughout the winter.
And 10 years ago, that would have been unheard of. So things do change over time. Thinking about the individual level, it certainly seems to be the case that the more we study birds on an individual level, whether that’s by marking them with something like coloured leg rings or these days, things like satellite technology and GPS technology, they’re allowing us to look on the individual level, the exact routes that birds are taking throughout migration. And firstly, within a species, different individuals might take a different route. So European breeders might go to Africa. They might cross the Mediterranean in different ways. All the same species, but technically different. Even more complicated, and a good example might be the cuckoo.
There’s been a quite high profile British Trust for Ornithology study of cuckoos using satellite tracking recently, has shown that the same individual might take a different route in different winters. So you’ve got a British breeding cuckoo, it’s going to winter in the forest in Congo, but the route that it’s taking to get there varies from year to year. So things are probably more complicated than we first appreciated. And of course because some of these birds at least will be carrying flu, it means that bird flu is also migrating as the birds migrate. The bird flu is moving around.
So that means that there are opportunities along the way for wild birds to pass those flus on to other wild species, wild birds of the same species, or other species that we might meet along the way. And also to agricultural birds like chickens and so forth if they happen to be in proximity to those. So is there much data about how much interaction there is between something like a migratory duck and farm animals? I think a lot more research is needed. I think it’s sometimes quite easy to kind of point fingers at wild birds. We know that wild birds are carrying bird flu and if there’s an outbreak on a farm, it’s quite tempting to make that assumption.
But I think we have to really think carefully about what evidence there is. It’s certainly true that there are opportunities for interaction. I think direct interactions– if you imagine a chicken farm, there’s often a lot of food around. And there will certainly be wild birds taking that food. But that’s mostly things like sparrows or starlings. And they’re not really known to be flu carriers in any way compared to ducks and so forth. And something like a house sparrow is not migratory. It’s probably spending its entire life on that farm. However things like the mallard, which as I said earlier, are some populations are migratory.
And we get a lot of wintering mallards that have come from further north and further east. They clearly do interact with farm ducks.
You see interbreeding going on between farm ducks and wild ducks. But probably at quite a low level. Also if there’s food knocking around, there are some duck species that will eat grain. Things like widgeon, and to some extent teal, will actually quite happily feed in grass rather than on water. And feed on grain. So I can imagine that– and I’ve certainly seen migratory waterfowl on farms. And also if there’s open water on the farm too, then migratory duck will use that water. But the degree of direct interaction, I think more research is needed. I think indirect interaction is likely. You certainly imagine a flock of widgeon flying over a farm to feed on some spilled grain.
And there’s going to be droppings. And I can imagine a lot of indirect interaction. But I think a lot more research is needed. Thanks very much for joining us today, Stuart. It’s been very interesting to hear about what an avian ecologist does. And I think it’s important that we realise when we’re studying influenza that this is fundamentally an avian disease, even though it does pop up in other species. And that we can’t really understand avian influenza unless we understand birds as well.