blue jays part 2: why are they chipping paint off my house?

paint chipped by blue jayRAT-TAT-TAT. And then again, from outdoors, on the front of the house. It’s far too early for the annual woodpecker ritual of drumming to assert territory; it’s winter, not breeding season. Was the same squirrel who’s been gnawing on the furniture on my back porch shifting focus (and had he somehow developed a rhythmic action to produce that sound)?

I sat in wait, determined to find out. The answer was a bit of a surprise:

It was a blue jay. And a few feet away, watching from a branch as the first bird chipped paint off a column on the porch, three companions cheered her on, as if awaiting their turns at bat.

But why? Maybe Google will know.

Though the original articles it refers to—from “Bird Watcher’s Digest” and Cornell Lab of Ornithology’s former membership publication “BirdScope”—are more than 10 years old and not online, this synopsis on Project FeederWatch provides the basic explanation:

Limestone, a source of calcium, is often an ingredient in paint (especially pale-colored latex paint birds prefer, apparently). The theory is that blue jays in the Northeast and Eastern Canada may collect and cache calcium in anticipation of increased needs in nesting season. Songbirds can’t store sufficient calcium in their bodies, and look to natural sources like snail shells, isopods including pill bugs and millipedes, and even earthworms—none of them easy to find right now.

(A related topic: In areas of high acid rain, those natural calcium sources have dwindled even when it’s not winter, posing a risk to nesting forest birds, such as ovenbirds, as appropriate habitat diminishes.)

eggshells for blue jaysHow to discourage paint-chipping? Offer egg shells, the various online threads suggest, specifically after sterilizing them by boiling or heating in a 250F oven for 20 minutes, to prevent potential salmonella transmission.

Really? But yes, of course I’m game.

Within 5 minutes of placing three sets of empty, halved, sterilized shells on the snow in the vicinity of my bird feeder, they were airlifted away, one after another. And yes, by guess who? And then again the next time I cooked eggs, and the next…

With smaller pieces of shell, or the paint chips, or for that matter bird seed, they load up awhile before flying off to hide the stash, putting the bits in their pouch-like “crop” temporarily. That’s what the jay, above, is doing with those kernels.

How the blue jays figured out the paint-chemistry connection seems to be unknown, as is how they knew those eggshells were on their grocery list. But remember: They’re in the same family as crows, and crows are really smart, too. That was the subject of Blue Jays Part 1.

  1. Vickie says:

    Very interesting findings there. Here’s something else you can add, and something I’ve often wondered about. I think your own findings have answered my questions. In the Spring, when I prepare my potting soil, I also add course vermiculite for drainage. I’ve noticed that once my newly potted plants are sitting on my patio, the Blue Jays sit on the edge of the pots and gobble up the vermiculite. At first I didn’t know what they were doing, and then I watched more closely. It was the vermiculite they were after. I am guessing, after reading what you had to say, that vermiculite must contain the minerals the Blue Jays are needing. I should be more generous and offer them a plateful of vermiculite. I think I will this year. So interesting.

    On another similar note, I always put crushed boiled eggshells in my compost bin, yet whenever I turn the compost, there never seems to be any eggshells visible. I think your experience has answered that mystery for me too. Thanks a lot.

  2. Edward says:

    A great article, thanks. My mother also used to put out egg shells that she baked in the oven for a while. All kinds of birds, including the chickens the eggs came from, would quickly make off with the egg shells.

    A quick note for Vickie, Some brands of vermiculite have been found to contain asbestos, so check it out carefully before buying it.


    1. margaret says:

      Thanks, Edward, for the hello, and the story of your mother’s offerings. RE: vermiculite — I see the EPA bulletin from 2014 about vermiculite in insulation that contains asbestos and a 2003 CDC bulletin about the contaminated vermiculite from the one mine in Libby, Montana, that was closed (I think sometime in the 90s, not sure). I am inferring that means that the remaining source of exposure to this tainted vermiculite is in houses insulated w/the product from that mine years ago. Hoping so.

  3. Sarah says:

    Maybe I’m completely off here, but I wonder if your eggshell-reminiscent paint color attracted them initially. Would they have been less likely to take a taste of a porch painted bright red or black, for instance? Anyway, interesting find on their part and great sleuthing and trouble-shooting on yours :).

    I like the idea of putting out eggshells as an alternative. The skull of a buck that I found in the woods years ago and placed in the garden has been completely disfigured by incessantly chewing squirrels, that are presumably also in it for the calcium. I wonder if they, too, could be tempted away by eggshells.

    1. margaret says:

      Yes, you are correct, Sarah, they like light-colored paint. The squirrels here are at an all-time high, so don’t get me started on that subject! :)

    2. Vickie says:


      I am wondering if those squirrels of yours aren’t simply sharpening their teeth on that buck skull? I’m guessing that’s it because the squirrels in my front yard have been using the boards on my front porch for sharpening their teeth. My carpenter soaked the areas with mineral oil and they stopped. Hate to remove their sharpening instruments. I tossed a piece of 2 x 4 out in the yard and they’ve been chewing on it. We learn something all the time, don’t we?

      1. Sarah says:

        Interesting idea, Vickie. That hadn’t occurred to me. I tend to think they are going for calcium, or other minerals in the bone, especially since there is lots of wood around to chew on if they felt like it–but who knows. I jus wish the squirrels would leave the vegetables alone. They, along with raccoons, rats, and Bermuda grass, are the bane of my gardening existence :).

  4. Sue says:

    What a coincidence! Blue jays have been messing about on my roof (standing seam metal) in Virginia. I also heard the rat-a-tat-tat and was looking around trying to figure out WHAT that was. Blue jays. There are a fair number of them here–rural area, crunchy cat food for the outside cats, a compost pile with those egg shells in it–but I’ve never observed this behavior before. It went on for several days about a week ago but seems to have stopped.

  5. Kathy Sturr of the Violet Fern says:

    So interesting! I am missing my birds – my bluejays – while migrating. I am hoping all are fairing well without me but I bet they miss the peanuts I usually put out every day. I have lots of snails in my garden now (I remember I was excited when I spotted my first). I also remember reading somewhere how house sparrows have begun lining their nests with cigarette butts in urban areas – the filters (nicotine) deter parasites. Birds are certainly not bird-brained!

  6. Ursula Swierczynski says:

    I make my own suet cakes and always include crushed eggshells since I read years ago that birds need this when they are laying eggs to raise their broods. For the past few months, since the bluejays have discovered my suet cakes, they have been relentless in chopping away at
    the cakes, whereas in prior years they used to just visit the sunflower seed feeders.
    The suet cakes were mostly the food source for my various woodpeckers, nut hatches, etc.
    Not only have these birds loved the suet, but the juncos (known as bottom feeders) have
    learned to feed on the suet feeders as well as on my nyger feeders.
    Evolution in progress I call it!!!

    1. margaret says:

      Hi, Ursula. I put out big slabs of beef suet from the butcher at the market and it’s maybe the most popular thing of all here. And yes, the juncos are on all my feeders, too. Love the idea of your “evolution in progress.” Nice to see you.

      1. Linda hall says:

        The only bird who eats my suet is a little yellow rumped warbler…..the juncos eat whatever is dropped . So I guess the California juncos are not as evolved!

  7. tunie says:

    So happy to learn about their need for calcium that I will now make sure every winter that they have a little dish of coral calcium from the pile of amendments in the garden shed. Thank you!

    1. tunie says:

      PS: It is always amusing when ‘science’ is baffled by how birds or other members of flora and fauna, humans included, know how to eat what they need. We ALL do this intuitively. Why science has failed to recognize that the intelligence of nature and our bodies is so deeply vast that it will keep science busy, for…ever is itself a bit daunting. Nature is continuously evolving, after all. Hopefully scientists will follow suit!

      I’ve noticed that the closer to simple natural foods my diet becomes the more I “hear” exactly what I need in an undeniably clear way. And the more I listen and follow, the healthier I become. For wild creatures who are not destroying their palate’s with synthetic ‘food’ like engineered snacks, etc, (read Salt, Sugar, Fat: How the Food Giants Hooked Us. Eye-opening.), this is a highly evolved feature and at the same time super basic. We can all do this. end rant!

  8. Shawn says:

    Birds do this for all sorts of reasons — sometimes birds peck at wood shingles or decking to simply reach — and eat! — the insect larvae that’s been deposited there. We have woodpeckers who use our siding to call rat-a-tat tat on — their beaks make huge holes (argh for us homeowners), but their purpose is to make a loud and impressive sound to attract a mate.

    1. margaret says:

      Hi, Shawn. Certain woodpeckers do that on my house where there is carpenter bee larvae in “tunnels” waiting to hatch, too…but not in the deep freeze of winter. I have to tie reflective tape (like a mylar streamer) up high on certain spots on the house to politely ask them not to do it.

  9. Charlene says:

    So very interesting and I’m glad you were able to get to the bottom of it. This reminded me of the bluebirds attacking the side mirrors on my car last year. At first it was hilarious and fun to watch. Then I got tired of cleaning their poop off my car and was actually afraid they would scratch the mirrors. Google told me I was not the only one with this problem and was due to mating season. They were trying to rid the neighborhood of the competition, I guess. I solved the problem by tying plastic bags over my mirrors for a week or so. A bit of a pain to remove them every time I left and put them back on when I got back. Who’d have ever thought a bluebird could be a pest? I love them and would never want to lose them.

  10. Vickie says:

    Reading all these great comments, I couldn’t help but remember my childhood when my folks kept chickens. My Dad always provided those chickens with crushed oyster shells. This gives me an idea. Tomorrow, I will go to the feed store and buy some crushed oyster shells. I need another bag of bird seed anyway. I get the kind with black sunflower seeds. Then I will ask my butcher for some suet. We learn something every day thanks to all of you.

  11. Kathy from Cold Climate Gardening says:

    We feed crushed eggshells to our chickens instead of grit. But we don’t bake the eggshells, we microwave them. We just make sure the egg clinging to the shells is cooked, maybe 20 to 30 seconds. It seems like it would sterilize them just as well as baking in an oven would, but I’ve never seen official confirmation of that.

    1. Deborah Banks says:

      We’re afraid to give egg shells back to our chickens. I have read that it “teaches” them to eat their eggs. We give them crushed oyster shell from the farm store instead.

      1. Sarah says:

        For what it’s worth, Deborah, we’ve been giving crushed eggshell back to our chickens for years. We have yet to have an issue with one of the girls eating their eggs. I think the main problem would arise if an egg accidentally broke in the nest box, and they discovered the tasty insides!

  12. ljfq says:

    One year we had a squirrel who repeatedly visited our deck to nosh the white paint off a bench. He also nibbled our bristly coir welcome mat all winter long!

    1. margaret says:

      Thanks, Sheri. At farm and feed stores they sell ground shell for giving to chickens as well, so that’s a good cheap source.

  13. Janet says:

    Margaret now you have me thinking about our Sulphercrested Cockatoos here in Australia. They are great paint eaters, especially around windowsills. Highly destructive. I now wonder if the paint too contains an ingredient they are seeking.

    I am now on a search to find the answer. Terrific to read about the Blue Jay.
    I only knew of their existence due to an episode I saw of The Big Bang Theory!

    1. margaret says:

      I bet it is the same reason — the way scientists found out about this in the US and looked into it about 12 or 15 years ago was when homeowners called in to the local chapters of various birding organizations like Audubon Society. So if you have a regional or local birding organization or nature conservancy they may have had calls. Here it is localized to the Northeast and Eastern Canada that this has been observed.

  14. Carole Clarin says:

    About the egg shells in the compost… I wash, actually rinse, my egg shells before throwing them into my compost pile. Am I contaminating it by not boiling or putting them in the oven? I never even thought about birds going after them. Oh dear! From now on I will boil. Then again about the woodpecker, one was pecking on my wooden siding several weeks ago-seems rather early in the season.

  15. mimimary says:

    I see bluejays constantly taking egg shells out of my compost pile. They aren’t sterile by any means but that doesn’t seem to deter them.

    1. margaret says:

      I’ve never seen them do it (my heap is far from the house) but that’s interesting, Mimimary. I have to say I have come to enjoy these loudmouth, bossy birds since discovering this new aspect of them.

  16. Patrick says:

    I enjoyed the topic and comments. An experiment came to mind. Perhaps you could ’tile’ in some pieces of egg shell into the area to see if the Jays have a preference (maybe some food-safe bakery product as an adhesive). Maybe food-color the eggshell to see if color is a variable. Interesting subject, Thanks

    1. margaret says:

      Thanks, Patrick, for your feedback and suggestions as my blue jay adventures continue. Just put out 4 more half shells today and again: gone within 5 minutes. Hilarious!

  17. Polly says:

    How are you putting out your slabs of suet? I just bought a hunk at the store, and am wondering if I should stuff it in a suet cage or tie it to a tree. Here’s another interesting Blue Jay note: I saw one eating snow that was laying on a branch. I thought birds had to find open water all winter. Guess not. Thanks for another excellent piece.

  18. Diane Richardson says:

    I have a very serious Blue jay paint eating problem. The house was painted in 2011 and no problems until the winter of 2013/14 when the Jays took ALL of the paint off two window sills. I asked for help from the Audubon society and they suggested oyster shell. No luck. As soon as ground was bare they stopped. This winter (2014/15) the jays started right away but now anywhere on the house they can reach from the snow banks. They have essentially destroyed a $3000 paint job. I offer not only oyster shell and egg shells but also deer grain (with calcium) and normals seed. Nothing stops them at all. 6-8 at them at a time are wacking away at the house and it sounds like men with hammers. I can scare them off but they come right back. The USDA is willing to give us a depredation permit to allow us to shoot them but I’d really rather not

    1. margaret says:

      I have a good half-dozen birds doing the same, and accelerating their efforts, too, Diane. Insane. I made egg salad for an event Saturday — 3 DOZEN eggs — and put out ALL the shells afterward…and ALL were gone that afternoon. I kid you not. DEMONS!

      1. Diane says:

        well I have given these nasty birds all forms of calcium as I said , oyster shell, egg shell, cage bird grit, cuttle bones etc.
        They completely ignored the oyster shell. barely picked at the other things. The squirrels lugged off the egg shells.
        The BlueJays are just totally obsessed with the paint. Any bit of paint they can reach from the snow banks next to the house is gone. In fact they have stripped ALMOST ALL the paint from about a 6-12″ area around 3 sides of the house! Nothing stops them at all
        The house was just professionally painted in the fall of 2011 it should no way be destroyed yet

        1. margaret says:

          Oh, Diane, what a sad tale. I have read that in some cases the birds will not be deterred. So sorry. Mostly they ceased here after a billion eggshells. :) Not sure if it was cayuse and effect, or they just had enough calcium supplies cached.

        2. Sam says:

          Same thing happened to my house. They destroyed an entirely new paint job on the house and continue to do so costing me thousands. I put out eggshells, seed with calcium, etc. Nothing stops them. Wouldn’t want to seek to have them shot either but I can not take them destroying yet another paint job. Did you have them shot?

          1. margaret says:

            It’s illegal under federal law to trap, kill or even relocate any native non-game birds including blue jays, under the Migratory Bird Treaty Act, fyi. One thing I can suggest: buy an inexpensive roll of mylar bird-scare tape (like this) — they have it at many hardware/home store places — and thumb-tack some streamers of it to the affected areas, or put it on bamboo poles stuck in the ground alongside, so it flashes. No birds like that it seems. Keeps woodpeckers from hammering the house, too.

  19. Frances Seth says:

    I tried putting the eggshells I had saved for many weeks. So far, there are no takers. It’s either too late or maybe too early.

  20. Lynn says:

    Wow great info here – thanks so much!

    I’d been watching the bluejays eating the paint away and thought perhaps my patio wood had bugs in it.

    Has anyone thought of hanging one of those calcium things that are used in bird cages – I think they’re called cuttlebone?

    1. margaret says:

      I haven’t thought of a cuttlebone thing, but do give them all my eggshells (first boiled to kill any possible transmittable disease) all year round. Every single one I put out disappears quickly, and I often catch sight of the bird flying with a beak full of a half shell. Hilarious!

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.