Bluebird and Small Cavity Nester Conservation
Sialis - Bluebirds and other small cavity nesters

Why is a bird eating the mortar between the bricks on my house?

QUICK TIPS: Some birds use grit to help digest seed hulls and insects with hard exoskeletons, or they may seek it out because they are sick.

mortar in brick wallA homeowner reported House Sparrows eating the mortar of my brick house. She said:

"I have had some of the mortar replaced and they’re eating it again. In places, the mortar is eaten/picked out as deep as 5 plus inches. One of the bricks can be lifted completely out. I’ve tried a reflective silver tape sold to me by a wild bird center. Then found the silver tape beautifully adorning a nest – designer birds! I also put phony snakes out – did not deter. What can I try? Will an artificial owl deter them if put on the roof?"

I don't know how her problem was ever resolved, but sometimes birds will eat the grit/sand in old, soft mortar between bricks to aide with digestion. Grit can come in the form of sand, insoluble small stones. I've seen tree and barn swallows picking up grit in my dirt/stone driveway. Birds usually prefer small grit and angular oblong grit more than rounded/spherical, and yellow, green and white grit.

After consuming grit, it is stored in the crop/gizzard (the ventriculus) where it helps break up food like seed hulls and insects with hard exoskeletons.

Crushed oyster shells (a form of soluble grit) are often offered to domestic birds as a source of calcium. I add ground up chicken or duck eggshells to my suet mixes to help build strong eggs and bones.

Healthy passerines (like House Sparrows and Starlings) do not require grit. If birds are eating grit, they may have digestion problems, pancreatitis, diarrhea, or diseases and parasites (e.g., Candida, Avian Gastric Yeast, Gizzard Worm.)

More Info and References:

True Grit
- Charles Portis

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