Attracting birds Birds

Curious Green Hump Under a Bird Feeder

Question: A curious phenomenon occurred at my house after I installed a bird feeder. A few days after installation, the ground began to rise up directly under the feeder, where the seeds the birds drop fall to ground.

Can you explain this? I’ve attached a photo.


Answer: In fact, it’s not really that the ground is any higher, but rather that the grass is growing there faster than elsewhere, so it looks like the ground heaved up. And that happened because of bird droppings.

Birds feeding at bird feeder.
Birds leave a surprising amount of debris under their feeders. Photo: Wirestock, depositphotos

Birds don’t have the slightest qualms about pooping where they eat. And at a bird feeder, where the population of feathered friends is considerable, things just seem to go in one end and come out the other. These mineral-rich droppings fall to the ground and feed the grass below. As you saw, the lawn often reacts very rapidly, growing more quickly and therefore displaying taller leaves. Hence the hump you saw.

Also, birds are messy eaters and the seeds and seed shells that drop from their beaks also fall to the ground and contribute to this enrichment. And they do add some height to the soil: over time, due to their thickness, seeds and waste will actually raise the ground a smidgen. However, seeds and seed refuse aren’t immediately available to the hungry plants waiting below. A good part of the minerals from bird droppings are in a form plant roots can absorb and are immediately assimilable. The remains of seeds, however, have to decompose beforehand and won’t feed the lawn much for several weeks if not months. So, in the early stages, probably they don’t yet contribute to the growth of grasses, or if so, only very little.

Too Many Minerals Are Harmful

That said, the opposite will soon happen if you always leave the feeder in the same location.

Bird droppings are so rich in minerals that their concentration eventually becomes toxic. As a result, the grasses under the feeder will soon begin to turn from green to yellow and then die. And that will eventually leave a patch of bare brown soil where the grass melted away.

Ideally, you’d change the location of the feeder regularly so that mineral applications are spread more evenly. That way, the whole lawn will get its share without a risk of minerals building up to toxic levels. Or you could leach the soil under the feeder by rinsing it often with fresh water to dilute the excess minerals.

Seed-catching hoop under bird feeder with birds present.
A seed-catching hoop helps prevent droppings and seed debris from landing on the lawn. Photo:

Another option is to hang a seed hoop, available from bird product suppliers, under the feeder to prevent any droppings or seeds from falling to the ground.

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, will continue its mission of demystifying gardening and making it more accessible to all.

5 comments on “Curious Green Hump Under a Bird Feeder

  1. hello, your article is so good.Following your site.

  2. I cut a perennial bed last year under a feeder. What a lovely surprise when 100+ sunflowers sprouted in the new bed. I was thrilled! The perennials still survived, obviously got a little choked out last year but they’re doing well this year.

  3. Any chance the green hump could be moles or voles?

  4. Patricia Evans

    At my house that seed catching tray would last about or 2 days before the squirrels brought it down. It is a great idea, though.

    • Yep, those pesky little buggers think we put it there for them!

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