Garden chickens and biodiversity – some thoughts

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Keeping chickens as a hobby is very popular at the moment and many gardeners are finding space for a few chooks in their own patch.  It’s been particularly trendy amongst urban gardeners, ourselves included: we have a run with 6 hens that make us self sufficient in eggs and chicken shit (the latter a vital addition to our soil’s fertility).  They are also fascinating, relaxing animals to watch as they go about their chickeny business of scratching, pecking, clucking, and dust bathing.  They are intelligent, social, inquisitive birds, that I’d recommend to anyone who has the space to accommodate a decent sized run and (importantly) the time to look after them.

There are plenty of magazines, books and websites offering advice on keeping hens on a small scale.  One of the most active and interesting blogs is The Garden Smallholder which generally has some good advice and ideas.  Back in November, however, a post about preparing a new kitchen garden caught my attention, specifically the fact that the writer’s chickens were let out onto the plot and that:

Chickens are great at scratching and turning over soil with their enthusiastic feet, and excellent pest control too

Let’s think about that last point, that chickens provide “excellent pest control”.  It’s a statement that I’ve seen repeated many times in books and articles, and it usually doesn’t solicit any comments.  But the logic behind it is that hens can differentiate between “pests” and “non-pests” in a garden, that they will gobble up the slugs and cutworms, leaving behind the worms, beetles, spiders, and other beneficial (or neutral) invertebrates.  This is nonsense, of course: chickens will eat anything they find and do not differentiate between the different elements of soil biodiversity*.

For this reason we don’t allow our hens to free range on our vegetable patch: we want to keep the soil’s fauna intact, allowing the earthworms to aerate and turn over the soil, let the beetles eat the slugs, give ground-nesting bees some space in which to live, and so forth.  A few weeks of digging with chickens present would destroy all of that.

The vast majority of invertebrates that live in the soil are not pests and a significant  proportion are certainly good for our gardens (particularly the earthworms and carnivorous beetles).  Allowing your chickens to feed freely on these animals will significantly reduce your soil biodiversity, which is a bad thing in its own right (if we accept that these animals are a measure of your soil’s “health” and productivity), and could reduce the numbers of invertebrate-eating wildlife, such as thrushes, hedgehogs and toads, visiting your garden.

If you want your chickens to eat garden pests my advice would be to take the pests to them: scoop up several slugs with a trowel, throw them into their run, and watch the birds excitedly scramble for their treat.  But remember that slugs play a positive role in the garden too, demolishing huge amounts of garden waste in compost bins and (in our garden) eating up cat shit.  That’s a topic for a future post though.


*I made a comment to this effect on the Garden Smallholder post but the blog owner saw fit not to allow it to appear.  Draw your own conclusions from that.

20 thoughts on “Garden chickens and biodiversity – some thoughts

  1. Clem

    I see your point in questioning whether chickens merit “excellent” in describing their abilities as pest controllers. But I wonder whether there might be some more nuanced way to measure their contribution in the realm of impacting the garden space?

    A fixed space for the chickens to run will certainly change in time to a very different ecosystem, much like a dry lot at a dairy, or an overgrazed paddock on a sheep farm. Rotational grazing sets about to prevent exactly this. And I’ve seen a few examples of farmers building a portable coop so they might move their birds about a pasture before serious destruction ensues. Now this may not be practical in a suburban back yard, but it still makes me curious if a day or two of chickens on a patch designated as the coming season’s annual bed might cause all the trouble you’ve outlined here?

    And a bit off topic for this post – but have you seen the article about neonic seed treatments affect on beetles that eat slugs exposed to treated seeds? The slugs are not killed obviously, but the predatory beetles seem to take the role of birds of prey eating fish exposed to chlorinated hydrocarbons. I don’t have the citation at my fingertips or I’d include it here. If you have any trouble finding it let me know and I’ll dig it up.

    1. jeffollerton Post author

      Thanks for the comments Clem, you make some interesting points. Agreed, rotating chickens between different parts of the garden will have less impact on any one spot.

      But it doesn’t get over the fact that chickens are indiscriminate feeders and will eat whatever bugs and worms are present, not only the “pests”. Whether this feeding has a significant impact on a garden’s biodiversity will obviously depend on number of birds, size of garden, etc. As far as I’m aware there’s been no research on this, it would make an interesting project.

      I don’t think I’ve seen the study that you’re referring too; yes, please post the citation.

    1. jeffollerton Post author

      Yes in natural communities, but I can’t see that happening where you have a high density of predators in a small area, especially when the predator’s food is also being supplemented by a Supreme Being…. 🙂

  2. Pauline

    Of course you’re right. We are new to chickens, find them endlessly fascinating, but I’d rather chuck them a can of chafer grubs than let them eat all the earthworms. They seem to find some tiny things as they peck away, but they will eat chard as happily as chickweed.

  3. Pingback: Garden chickens and biodiversity – some thoughts | Jeff Ollerton’s Biodiversity Blog | World Organic News

  4. Ian Smith

    As I understand it (and is the case with cattle), you are meant to crash graze when there is an abundant food source. eg if your plants are being heavily damaged by snails, then releasing the chickens for a day or two will reduce the snail population down to a level that is manageable to other beneficial species. As you said however, Intensive predation helps no one.

  5. adrianstockdale


    An interesting article. I have wondered, if through a rotation cropping system, the chickens could turn over a fallow plot whilst you cultivate the remainder. This would add the fertiliser whilst tilling and clearing the plot. The downside being you require more space to crop. That said lawns may contribute to global warming so is that a bad thing? I agree it would be interesting to see trials on this.

  6. Helen

    I doubt I have room for chickens but my own eggs would be wonderful.

    Sad that your comment didn’t appear but at least you are getting the message across to those who read your blog about what chickens will really eat and why slugs might actually be a good thing in the garden. They certainly seem to enjoy my compost heap!

  7. kathandroger

    Chickens are useless on all gardens and allotments! Just like goats they will eat everything except what they are supposed to eat. And how do you know that they improve your soil fertility?
    That being said, I love chickens! Each has its’ own personality, the group interactions are fascinating, eggs are good for us, and having a cock and chicks is a joy to everyone. They take very little time to look after.
    Life is compromise, we accept the damage to our plants in exchange for the pleasure we gain.

    1. jeffollerton Post author

      “how do you know that they improve your soil fertility?”

      Well, by the same token I could ask, how do you know that “eggs are good for us”?

      It’s a matter of understanding the chemical nature of what you’re putting into the soil or your body. In the case of chicken manure, it’s high in nitrogen and, mixed with straw from the coop, is a useful addition to our compost heap.

      I didn’t touch on plants in the post but, agreed, chickens are just as destructive of the garden flora as they are of the fauna.


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