Monday, September 18, 2006

The True Grit of Sparrows

Monday, September 18, 2006
A male house sparrow on a nest box it stole from bluebirds. (Boo! Hiss!)

Some birds will do anything for a little grit.

Birds have no teeth for crushing food items, so they utilize small, hard pieces of stone, eggshell, or sand as an abrasive digestive helpers. This is known as grit. Grit is consumed and housed in the bird's crop where it helps to break up food. Grit is a commonly consumed staple especially for birds that eat lots of seeds or insects with hard exoskeletons.

We see lots of examples of birds eating grit.

Our barn swallows spend most summer afternoons sitting on the front yard powerline, waiting, like vultures at an abattoir, for us to throw some eggshells onto the sidewalk and garage roof. I've seen evening grosbeaks hit along winter roadsides where they were ingesting small bits of rock salt and cinders. I've seen purple martins, aerial insect eaters, scarfing up eggshells from feeding platforms during the breeding season. We've even published articles in BWD about paint-eating blue jays! All of these birds are after grit to aid their food processing.

As a kid, in the early 1970s, I often noticed house sparrows clinging to the brick foundation of the neighbors' house and I wondered what was up. It was years later that I figured out that they were getting dietary grit from the sand in the mortar between the bricks. The old mortar was just soft enough for the hefty-billed sparrows to nibble away at it. If this went on forever, in theory, all the mortar would be consumed and the house would tumble to the ground. But the neighborhood cats and the resident sharp-shinned hawk probably kept the house sparrows in check, so the house is still standing all these years later.

On a recent visit to my parents' home I noticed that the foundation bricks on the neighbors' house had been painted gray. Standing in stark contrast were the pale divots between the bricks where the sparrows were still getting their grit--30 years after I first noticed it. And who knows how long the sparrows have been at it there. Certainly the first house sparrow that discovered this particular grit source is long dead. But I'll bet some of his or her great-great-great-great grandbirds are still here munching mortar!

And how cool is that?

If you look closely you can see a male house sparrow getting his grit, slowly demolishing this house one nibble at a time.

A close-up view of the sparrows' grit-gathering site. It would be interesting to compare these HOSPs to others that do not get their grit in this fashion. Have they worn down their bills accessing the grit? Over time, would a sparrow evolve with a bill like a bricklayer's trowel?


On September 19, 2006 at 11:29 AM Bill of the Birds said...

I should add here that our barn swallows and the purple martins I've seen elsewhere derive another benefit from consuming eggshells: calcium. This aids in the development of eggs during the nesting season.

On September 19, 2006 at 11:58 AM Rondeau Ric said...

So, they are the John Wayne of birds?

On September 19, 2006 at 11:31 PM Susan Gets Native said...

Oh, the little buggers are everywhere!
You know, I would love them if I were in England. But they mess up my bluebirds and eat all of my expensive seeds and I don't like how they look and I just hate 'em.
whew...I feel better.
When I read that my parakeets don't really need grit, since they shell their seeds, I started using the huge box of grit I bought out for the birds. They seem to approve.

On October 10, 2006 at 8:39 PM Bob Lieske said...

I have the problem with the sparrows consuming the mortar. Wonder if you, or anybody out there has a I'd like to keep my house standing. It's a pretty red brick house so I don't intend to paint the bricks. Maybe just replace the mortar and coat it with something that the birds don't like?


On September 4, 2007 at 11:12 AM Anonymous said...

Never seen your site before - just been given a link by our collater here in Gateshead in N.E.England in reply to my query having seen the little buggers(sorry spuggies) at it on my wall in Northumberland having never noticed it before in nearly half a century's birding (I'd always assumed they were eating spider's eggs like the Tits (hope you have the Parus species in the US or that's embarrassing!) I suppose we probably introduced Passer domesticus to the Colonies? The mortar on that particular wall was pinkish -similar to your photo- don't know if there is any significance; I'll try and attach the original photo if I can. Cheers

On June 23, 2008 at 4:42 PM Anonymous said...

My husband and I, along with a few other neighbors, are having this problem with the sparrows eating the brick along the foundation of our homes. Any solution on how to stop this without harming the birds?

On November 9, 2010 at 2:55 PM Anonymous said...

We live in an urban area and we have problems with sparrows eating bricks along our row houses. They have managed to eat through some substantial portions of brick.

I would also like to know if anyone has any suggestions for this.

On July 16, 2011 at 1:52 PM marge daley said...

I too am having trouble with sparrows eating the mortar between the bricks on both sides of my side door. Painting the brick is out of the question as my whole house is brick. Does anyone have a solution to deter them? I don't want to pay a tuck pointer to repare the damage only to have them start eating all over again. Would appreciate hearing of a solution. Thanks
Marge Daley

On July 16, 2011 at 2:06 PM Bill of the Birds said...

Among the solutions worth trying are: re-mortaring the brinks with newer, more cohesive mortar.

Also, placing some tight-weave chicken wire about 5 inches from the wall will prevent birds from gaining access. If that's not possible, try:

Offering a source of large-grain sand for the sparrows to use for grit. Or

Placing some rubber snakes in the places where the sparrows are nibbling the mortar.

Good luck!

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