Interview with Sean Walls about the Common Buzzard in UKDate of the interview: March 30 2011 In this interview, Common Buzzard expert talks about the conservation and biology of the Common Buzzard in UK.
During the last 20 years Sean has worked for Biotrack which supplies tracking equipment for wildlife. During that time he has radio-tracked squirrels, sika deer, fish and more recently dragonflies. However, by far the longest study has been on buzzards that he tracked for 15 years to learn more about their dispersal.
Sean with Common Buzzard
© Peter Bell
Sean Walls: Very common in the west, and increasingly common in the east. According to the BTO around 40,000 pairs a decade ago, and there is every reason to believe it will have increased since then. Based on the number of pairs, this is a very healthy breeding population, but it is also worth remembering that there could be many more individuals than a survey of breeding pairs might suggest. A study I conducted with Prof. Robert Kenward on the south coast, found that only a quarter of the buzzards in our study area were breeding. Therefore, we would need to multiply our breeding pairs by 8 to get the number of individuals present. Whilst such a large proportion of non-breeders is unlikely everywhere in the UK, especially in the newly colonised east, the number of individuals is several times the number of breeding pairs. Markus Jais: How has the population developed during the last decades?
Sean Walls: Colin Tubbs monograph on the common buzzard goes into great detail about how the ups and downs of buzzard fortunes. A survey in the 1950s suggested 10-15,000 pairs, restricted to the west. The population then seemed to drop to less than 10,000 by the 1970s. The apparent decline was attributed to the introduction of myxomatosis that severely reduced the rabbit populations, hence decreasing the food supply of the buzzards. Since then, both the Wildlife and Countryside Act, that made killing raptors illegal, together with the changing attitudes of game keepers in many areas of the UK, has seen the population increase rapidly in the last 30 years. It is graphically demonstrated by the spread of buzzards from their western strongholds, back across the country right over to the eastern regions. It really has been a joy to see so many people enthralled with the return of this majestic looking bird. Markus Jais: What is the preferred habitat of the Common Buzzard in the UK?
Sean Walls: Buzzards are very adaptable, so there are not many habitats you won't find them in except built up areas and heathland. They still prefer woodland edges for nesting. This gives them both a high structure with cover in which to nest, but also open land for hunting rabbits and smaller mammals for feeding their young. However, they are perfectly capable of nesting on cliffs, or even the ground on an island with no mammalian predators and little human disturbance. There have also been cases of nests in isolated trees along a hedgerow.
Common Buzzard nest © Sean Walls
Sean Walls: Following on from the last question, buzzards need something to carry to their nestlings, and so during the breeding season the primary staple of buzzards is rabbits, small mammals and, in places, game bird poults. They do scavenge and so we have found sawn butchers bones (taken from the local rubbish-tip), squashed hedgehogs from the road etc. However, during the winter in southern UK (which I am most familiar with) it is amazing how many buzzards survive the winter primarily by eating worms. This may be a peculiarity of the UK, having a warm damp climate for the latitude, which means we rarely get frosts that last more than a week. The buzzard has a wonderful capacity to absorb energy from very poor food, as observed for centuries by falconers. Now we know that this is due to a proportionally long gut compared to other raptors. This allows these birds not only to live on worms (which many other raptors could not) but also to survive without eating much, to withstand the short frost periods we do get. Markus Jais: What is the effect of Common Buzzards on game birds like pheasants or grouse?
Sean Walls: Difficult to say in general because it seems to vary geographically. They undoubtedly will take whatever they can, but compared with other raptors they are not particularly fast, manoeuvrable or strong, and have relatively small feet to bind to prey. Therefore they find it quite an effort killing birds evolved to evade predators with a sudden, strong burst of speed. From what keepers say, they do take young pheasant poults from rearing pens, because they are in a vulnerable situation and poults are smaller and weaker than adults. Usually they do not take more than what they need to sustain themselves and their chicks. Therefore more enlightened keepers will accept that, and put out more birds to compensate for a relatively small loss. They will also kill some adult pheasants, but then they are unable to carry them to the nest, so it is no good for feeding young. I have seen buzzards worming next to domestic chickens, preferring the easy worm pickings than a struggle with something that might fight back. I have less experience of their predation of grouse, but the literature suggests that although grouse appear in their diet, they are not common prey. Markus Jais: Do Buzzards migrate during the winter in some parts of the UK?
Sean Walls: This is a very interesting question. Certainly past work has suggested that buzzards move off highlands to the nearby lowlands during the winter in Scotland, where the weather is much harsher. Our radio-tracking work showed individuals to move away from their nest in the first autumn, and then come back to the nest in the following springs, seemingly to check for potential breeding sites. But this was all very individual movements - not what would be recognised as a proper migration.
Good combination of arable for winter feeding, grass headland for small mammals and small wood for nesting.
© Sean Walls
Sean Walls: By radio-tracking buzzards from the time of fledging we have learnt a lot about their dispersal. For a start, not all young buzzards disperse in their first winter, but stay in the parent's territory until the spring. Others can disperse a long way, but will return again the following spring to the nest they came from, before heading off again to find a new area. This probably explains why some wing tagged buzzards, from earlier studies, seemed to disappear during the winter and were then seen again near the nest in the spring. Without radio-tags it was impossible to know whether they had just kept themselves less conspicuous (to avoid the attentions of the territorial birds) or whether they had actually moved away and come back again. Several birds were recorded visiting multiple springs, until they started breeding, often in the area in which they had last wintered. What was surprising was how much the dispersal distance appeared to be correlated with certain weather conditions when they left their parent's territory. High temperatures and winds from the south west corresponded with longer dispersal. Markus Jais: How does the Common Buzzard interact and compete with other raptors like Hen Harriers and Golden Eagles?
Sean Walls: I must admit I don't know too much about this. As I mentioned before, buzzards are relatively weak and less agile than other raptors, so they are not dominant. I've seen them being mobbed by kestrels and peregrines, and heard that cooperating kites can kill them. I'm afraid I'm not in an area where there are hen harriers during the breeding season, or any golden eagles, so I don't have any experience of their interactions. Apart from the usual wish of raptors to control the air space near their nest, they have quite different niches to those two particular species, so I would not expect much resource competition. I did once see an adult marsh harrier stoop on some weak fledglings that were learning to fly, but no contact was made. Markus Jais: What are the main threats to the Common Buzzard in the UK?
Sean Walls: Currently I don't believe that the buzzard is threatened at all. I'm sure there are local areas where they are not succeeding, but really the agricultural landscape we have created in the UK suits them very well, provided there are some trees in which to nest. Although the arable farming decreases the number of worms in the soil, they make worms more available by removing all the vegetation during the winter.
Typical worming during the winter months.
© Sean Walls
Sean Walls: Buzzards undoubtedly still suffer some illegal killing, and this seems to be worse in the north of the UK. Saying how many is almost impossible, because detection is difficult. From our radio-tracking study in the south of England, illegal killing was a minor cause of death, natural causes and vehicle collisions being far more important. In areas where poisons are put out for other species, buzzards are vulnerable due to their scavenging nature. Likewise, their slow soaring flight makes them an easy species to shoot. Whilst some still regard them as vermin, due to their hooked beak and talons, I have spoken to many keepers who do not regard the buzzard as such a threat. Markus Jais: Some people want to make the shooting of Common Buzzards legal again? What would be the effect on populations if this will be allowed?
Sean Walls: The effect would depend on how the law was implemented and enforced, e.g. whether you had to prove a problem with individual buzzards before being allowed to kill them. It is much simpler to have an absolute ban on shooting raptors. Buzzards seem to have re-colonised large areas since killing has become illegal, so presumably that would be reversed if unconditional shooting was allowed. On the other hand, I think attitudes have changed a lot in the last 30 years and so I think that more game keepers would be tolerant, and peer pressure would mean that the re-colonisation would not be completely reversed. In my experience, more people enjoy seeing buzzards than want to get rid of them. But of course you only need a small number of motivated individuals to severely deplete a local population, and if it is not illegal then the owner of a shoot will have every right to demand the elimination of a potential threat on economic grounds. Markus Jais: How do current agricultural practices affect the Common Buzzard?
Sean Walls: Current agricultural practices are just great for the buzzards. In early autumn we plough the ground, or at least cut the crops short, leaving the worms easy to see. Buzzards are so eager they quite often follow the plough with gulls looking for worms, in the same way that they follow a harvester looking for chopped up mammals. Admittedly, when spring comes and the crops grow then worms are no longer so available, but this is the time when naive young birds and mammals are becoming more abundant, so the buzzards switch to these prey for nourishment and feeding their young.
Typical good habitat for buzzards in southern England
© Sean Walls
Sean Walls: I don't believe much must be done except to maintain the current land practices. Currently, the UK is a good place for buzzards, although it's possible a decline in small mammals could decrease their breeding success. Markus Jais: What was your most amazing experience with Common Buzzards?
Sean Walls: I've been lucky to have many amazing experiences with buzzards. To pick one I would have to say it was seeing buzzards flying free in the east of England after a translocation experiment. The idea that these were the first buzzards seen there in a lifetime was truly uplifting, especially seeing them wheeling up, full of the anticipation of exploration. Markus Jais: Sean, thank you very much for the interview.