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 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.
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.