Worms or what? (1 Viewer)

[charlierocky]

Reading through some of the threads recently I have come across a few statements implying that the main food source of the common Buzzard (Buteo buteo) is the earth worm. I am not a scientist, nor have I the time or the resources to prove or disprove a statement such as this, but does a Buzzard really look like a worm eating bird? What should a worm eating bird look like? well...like a blackbird, a thrush, a rook, to name but a few. Take a look at the buzzard and you will see a sharp curved beak, strong powerfull legs terminating in large grasping talons armed with long sharp claws, a strong powerfull neck and shoulders...quite a bit of over kill in the design department if the main target prey were the common earth worm. Nature is rarley extravagant in giving any living species more than it needs to survive. Indeed, as far as I understand it nature operates a 'use it or lose it' approach to evolution, as we all know some birds have lost the power of flight when they desisted from using there wings. So if the Buzzards main food source is the earthworm, why has it not lost those attributes that would serve it well if it were to take on something much bigger. Is the worm eating Buzzard a myth?...or is the humble worm just a supplement to tide a capable raptor over lean times?

 

[neil brown]

i dont think i would describe the earth worm as the buzzards main food source but it certainly helps to get them through some lean periods. buzzards gathering on fields being actively ploughed are a common sight here in kintyre, with a record of 32 individuals in one field some years ago.

 

[lulie]

The common Buzzard is a generalist feeder and as it is a very wide spread bird it occupies a great variety of habitats. There have been extensive studies in to this bird and findings have concluded that it eats a very wide range of food items. It will take large prey ( rabbits ect) but this is quiet energy consuming so resorting to digging around in ploughed fields looking for worms, grubs, beetles, mice and moles, can be an energy efficient hunting method. What a buzzards main prey item is will be decided by the habitat and environment it lives in which is why different studies have come up with different results.
Your description of the buzzards hunting tools (beak and talons) is lovely but a closer look at a buzzard will show these tools as perfectly adapted to its mixed diet. As birds of prey go the buzzard is not that strong.

 

[MattM]

It's certainly not a myth, although worms are far from its main food source. As the other posters suggest, I think it feeds on worms when other food sources are scarce, or when the worms are really easy pickings. I've seen it myself on a number of occasions.
I've also seen Red Kites and juvenile Montagu's Harriers doing the same thing.

 

[razorsharp]

Yep, Kestrels do it too. Buzzards will eat anything they like if they can get it, whether that is a rabbit they have killed, a deer carcass, a mouse, a frog, a jackdaw or a worm, the buzzards eats to stay alive, worm or not.

 

[Capercaillie71]

I have wondered about this too since I first saw it mentioned on a thread (by Poecile I think). I've no doubt worms can be an important prey item for buzzards and other raptors, but I'd like to see a published reference that reports worms as the main prey item before accepting the claim.

Here in Aberdeenshire, during the breeding season, many Buzzards rely heavily on young Rooks as a food source for their chicks.

 

[razorsharp]

Okay I don't know if worms are main prey or not, but if a buzzard is standing in a field full of worms and there is know other prey around, I think worms wll be its main diet at that time. Worms are just as good as other prey as far as trhe buzzard is conerned.

 

[razorsharp]

Okay I don't know if worms are main prey or not, but if a buzzard is standing in a field full of worms and there is know other prey around, I think worms wll be its main diet at that time. Worms are just as good as other prey as far as the buzzard is conerned.

 

[pe'rigin]

Interesting what Capercaille has written about the Rooks, which I have not really considered. We have a Rookery and a pair of Buzzard nest in close proximity to them. The Buzzards can usually be located on the ground in moist conditions. They also favour a single post to hunt from which they take mainly rats and mice from the fields. Road kills and rabbits also feature, but they do grub about a lot, especially as a family unit in Autumn.

 

[KnockerNorton]

look up work by Robert Kenward on buzzards in Dorset. He's also the bloke who wrote the monograph on Goshawk. He told me about it. He told me it was about 3/4 of the diet of the birds he was radiotracking.

I see there's a paper in the new Ornis Fennica on buzzard diet in Sweden (or Finalnd?), judged from video recordings at the nest and pellet analysis. This makes no mention of worms and instead says medium-sized birds are 3/4 of the diet. But you wouldn't find remains of worms in pellets, orr probably video analysis at the nest. They are likely to bring bigger prey back to the nest and eat worms themselves, or the worms will be too small to see on a video from any distance. I think this is a major flaw of most diet analyses, by focussing on the nest and pellets - at other times of the year and away from the nest you can't tell what they're eating, and worms leave little/no trace. These studies usually concede (as the Ornis Fenn does) that they're underrecording amphibians because the bnones get digested and aren't passedin pellets, so they record more amphibs on video than they can account for in pellets.

So I'm just going by what Kenward told me, and he'd be the bloke to know. It may be restricted to Dorset, England, UK, or just the brids he was following, but seeing as Buzzards breed at high densities, they're not all living off mammals and birds - there aren't rnough. Kestrels are also big insect eaters, and especially Lesser Kestrel, so it's not unprecedented.

I've seen buzzards follwoing a plough! And you often see them skipping about on pasture/ploughed fields. They're not chasing rabbits...

 

[Strandman]

I see there's a paper in the new Ornis Fennica on buzzard diet in Sweden (or Finalnd?), judged from video recordings at the nest and pellet analysis. This makes no mention of worms and instead says medium-sized birds are 3/4 of the diet.

That's interesting- someone mentioned to me last week that the Common Buzzards in the old forest within Bialowieza hunt below the canopy and take a high proportion of small to medium birds, including thrush spp. The suggestion is that this was the traditional Common Buzzard ecology before extensive forest clearance and the now better known behaviour of worm and rodent catching over arable and other open land.

 

[KnockerNorton]

Just had a skim through this paper:

Life Path Analysis: Scaling Indicates Priming Effects of Social and Habitat Factors on Dispersal Distances
R. E. Kenward, S. S. Walls, K. H. Hodder
The Journal of Animal Ecology, Vol. 70, No. 1 (Jan., 2001), pp. 1-13

that deals with buzzard movements. kenwards fround a strong tendency to hang around short grassland and loamy soils, linking this to their feeding on worms. He also quotes Dare (1957) 'Devon Birds' thus: "buzzards spend much time eating worms and other invertebrates". I don't have access to Dare, so can't see what he says. But Kenward has done a lot of radiotracking/behaviour papers on buzzards (with Sean Walls) - they followed them in landrovers and observed them directly after finding them using the transmitters.

 

[KnockerNorton]

That's interesting- someone mentioned to me last week that the Common Buzzards in the old forest within Bialowieza hunt below the canopy and take a high proportion of small to medium birds, including thrush spp. The suggestion is that this was the traditional Common Buzzard ecology before extensive forest clearance and the now better known behaviour of worm and rodent catching over arable and other open land.

or maybe they're taking juvs etc juring the breeding season? Sitting targets, young thrushes.

 

[charlierocky]

That's interesting- someone mentioned to me last week that the Common Buzzards in the old forest within Bialowieza hunt below the canopy and take a high proportion of small to medium birds, including thrush spp. The suggestion is that this was the traditional Common Buzzard ecology before extensive forest clearance and the now better known behaviour of worm and rodent catching over arable and other open land.

This type of situation would explain why the Buzzard still looks like a raptor that is capable of taking bigger prey. The worm feeding Buzzard is reacting to the relatively recent deforestation of some of it's domain and the reduction therefore of it's 'normal' prey (smaller birds). But is'nt a Buzzard a very large bird to be operating beneath the tree canopy where it's huge wingspan would be a disadvantage?

 

[KnockerNorton]

This type of situation would explain why the Buzzard still looks like a raptor that is capable of taking bigger prey. The worm feeding Buzzard is reacting to the relatively recent deforestation of some of it's domain and the reduction therefore of it's 'normal' prey (smaller birds). But is'nt a Buzzard a very large bird to be operating beneath the tree canopy where it's huge wingspan would be a disadvantage?

I think you're making a supposition too far there, re 'normal diet'. Who knows what they ate or at what density? I doubt they've changed their habits much - they are still basically inactive soaring and perching birds that wait for food to pop up rather than dash about after it like a hobby/sparrowhawk.

The short tail and broad wings tells you they're soarers, and not built for darting about between tree trunks cf Goshawk (which already fills that niche). There would have been plenty of clearings in the orignal forest, from tree falls, at the edge of marshes and on seasonal floodplains, where fire had struck or large animals thinned out the vegetation.

 

[lulie]

Both The Birds of the Western Palearctic concise edition and Raptors of the World books mention earthworms in the very diverse prey items of the common buzzard. They use terms like 'adaptable feeder' and 'versatile feeding techniques'
There is really no mystery to this bird. They are generalist feeders and this is reflected by their abundance all over europe, along with the other widspread generalist the Black Kite.
What ever appears as the primary prey item is purely down to availability, time of year and habit.

 

[KnockerNorton]

Both The Birds of the Western Palearctic concise edition and Raptors of the World books mention earthworms in the very diverse prey items of the common buzzard. They use terms like 'adaptable feeder' and 'versatile feeding techniques'
There is really no mystery to this bird. They are generalist feeders and this is reflected by their abundance all over europe, along with the other widspread generalist the Black Kite.
What ever appears as the primary prey item is purely down to availability, time of year and habit.

...and ability of researchers to detect it.

 

[DEREK.C.]

A few year ago, A pair of Common Buzzard moved into my local patch, a large area of mixed woodland . Yet the amount of times they are seen in the wood itself you can count on one hand.The Two areas they prefer are both open areas and grazed by cattle, with a few scattered trees.
The only thing i have ever seen them kill was a young Rook, taken from the nest, apart from that i`ve only ever seen them take roadkill.
Although the area they prefer of short grassland with cattle , does suggest
worms could be on the menu, although never seen. Kestrels eating worms is a common sight.
One thing,the local bird population dosent seem too bothered by Buzzards , one day i saw one fly into a tree full of Wood Pigeon and Stock Dove to perch, and the pigeons didnt bat an eyelid . They must realise they dont pose a threat.

 

[Himalaya]

i for one would love to know more aout the buzards diet......they seem far too slow at caching rabbits.....yet they do.....

in BBC Spring watch it was claimed that the male barn owl had been huinted by a buzzard........does anyone remember that?

 

[nirofo]

Well I certainly don't think earthworms form anywhere near the Buzzards main diet, but I do see one regularly from my kitchen window working the field looking for worms. The bird looks most comical and ungainly with it's waddling walk and wings drooping at it's side. Seriously though the earthworm is just one of the many different food sources that make this bird so successfull! If only the keepers and poisoners would leave them alone.

nirofo.