Bird vs. Bush – can there be too many birds?

Silverberry is quite a resilient shrub, but there are cases when something as innocuous as a tiny sparrow will bring it down to its knees…

Numbers is the operative word here, since when an entire flock sets down on a shrub or  bush too often, unexpected consequences arise. Keith Hall, a Nature & Garden contributor, shares a rare experience with us.

Silverberry, not your usual grunt of a shrub

Silverberry, a member of the Elaeagnus family, ordinarily stands out against all other shrub types thanks to its hardiness, resilience and weather-worthiness. Its near cousin, Russian olive, is actually deemed invasive in some parts because it’s so hard to kill off.

But in this particular case, a healthy, well-settled in silverberry bush was sent teetering on the brink of survival by a simple flock of sparrows.

Silverberry bush branches die off

Lower branches dying and dropping off during the growth phase of an otherwise healthy silverberry shrub.For some reason, a well established silverberry bush started dropping new growth and the once solid bush saw entire branches turn dry and die.

Yard-long branches of old growth yellowed and browned into a crisp, crackly mess while other branches seemed unscathed.

Might a fungus or disease be attacking the silverberry?

Disease always starts somewhere, but several other silverberry bushes in the near vicinity didn’t seem to show the slightest hint of damage.

What about competition for water?

Silverberry is actually the type of bush that normally succeeds in out-competing its neighbors for water and nutrients, and is usually quite drought-resistant.

This particular bush, though, had two hawthorn bushes and two other trees within a ten yard (ten meter) radius. Together with a two-month heat wave, these plants certainly exerted competition for water, resulting in possible water stress for the silverberry.

However, Keith, with quite a bit of foresight, watered the bush abundantly, which probably saved the bush in the end.

Clues leading to the culprits

Two clues sent the investigation off in an entirely different direction:

Massive amounts of birds on bush

Over a hundred birds seemed to fly in and out of the bush on a daily basis. They were flying to and from the silverberry shrub on the way to a loaded bird feeder that was a couple yards out. This shrub just happened to be the nearest spot for cover when approaching the feeder from further out.

Droppings like a guano phosphate mine

Leafless passageway carved out in a solid silverberry bush by sparrows incessantly flying through.The sparrows, while they didn’t roost in the bush overnight, certainly spent a large part of the day there, zooming in and out of the shrub to the point of carving out a tunnel in the previously solid leaf cover. Branches at entry points to and from the shrub grew stunted leaf buds or died off under the constant wing pressure.

At the foot of the shrub and along the branches, uncountable traces of droppings showed that these birds were definitely enjoying their free lunches.

Do birds ever kill trees?

Usually, birds never single-handedly kill trees. As with all things natural, a combination of factors unite and build up to a tipping point over time.

In this particular case, the following factors contributed to weakening the shrub in the first phase:

  • water stress from an ongoing two-month drought
  • heat stress from record summer temperatures
  • competition from neighboring shrubs and trees

But the crucial blow was the flock of sparrows itself.

Primary suspect: nitrogen burn-out

Accumulated droppings from the hundreds of birds cause extreme concentrations of nitrogen in the soil. Since the heat wave and drought were at their peak, any amount of water was loaded with concentrated nitrogen ions. This triggers imbalances in the root and sap system. Some roots send sap up to specific branches, and the branches die off wherever excess nitrogen upset this specific balance.

Watering abundantly had the advantage of diluting and washing out some of the decomposing droppings, which probably saved the bush.

All in all, too much “fertilizer” burned the roots of the mature silverberry, much as excess fertilizer kills seedlings off when planting in soil mix that is too rich. This also has been seen in the case of chickens penned in a coop under trees for a long time.

Apprehending the culprit, rehabilitation and recovery

Knowing the problem was already half the solution, and the following steps were implemented to get to the “root cause” (the bird flock) and help the bush recover – the “root solution”!

Here is what works to drive birds away

  • remove or relocate the feeder
  • empty it except during very cold weather
  • set up a scarecrow or bogus raptors, but this is only effective for a few days.
  • hinder the birds’ flight with a net or with a fishing line criss-crossed among the branches.
  • plant more berry trees in different areas of the garden.

Removing or emptying the feeder is of course the most effective, followed by the net and fishing line: birds don’t like getting their wings caught by the near-invisible obstacles.

The long-term solution is to plant different berry trees and shrubs in separate areas of the garden, to vary their source of food and stage it in time as seasons come and go. That way, the birds will have to shift their flight patterns around the garden and won’t shed their droppings on a single spot.

How to help the shrub recover

  • prune off dead branches
  • water abundantly
  • mulch the soil under the tree with wood chips

Pruning will keep the roots from sucking up too much water from the areas with a high nitrogen concentration, and will clear up space for new, healthy growth.

Watering will wash out some of the excess nitrogen.

Mulching with wood chips serves a double purpose. First of all, the fungus that work on decomposing the wood chips tend to consume a lot of nitrogen, so they’ll be absorbing and locking up excess nitrogen from the soil. Second, the mulch will release nutrients that will help the shrub bounce back.

In the end, since the issue was solved in the middle of the season, the bush has a good chance of growing back to its full, solid shape by the following spring. Case closed!

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Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Singing sparrow by Daniyal Ghanavati under Pexels license
Silverberry dying by Keith Hall,
Nature & Garden contributor
Silverberry with bird passage by Keith Hall,
Nature & Garden contributor