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Birds Gathering Grit On Dirt Roads & Roadsides

Birds compensate for their lack of teeth with a two-parted stomach, the first of which (proventriculus) secretes digestive enzymes and the second of which (a muscular gizzard) grinds the food they’ve eaten into small digestible bits.  Birds that eat hard seeds and nuts tend to have thick, muscular gizzards, while those species that eat very easily-digested foods such as soft-bodied insects, soft fruits, or nectar often have very small and thin-walled gizzards.  Many birds whose diet consists of hard substances, including seed-eaters, swallow grit (often why you see them on dirt roads or the sides of plowed roads where dirt has been exposed) to enhance the gizzard’s ability to pulverize food.

At this time of year, American Goldfinches, Common Redpolls, Snow Buntings, Tree Sparrows and Eastern Bluebirds (among others) can be found swallowing roadside grit to help grind up the seeds that they consume.  (Photo:  While a majority of their summer diet is insects, Eastern Bluebirds consume many fruits (containing hard seeds) during the winter, a change in diet that allows them to remain in northern New England throughout the year.)

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7 responses

  1. My Sister in Illinois has bluebirds at her suet feeder

    January 18, 2021 at 9:28 am

  2. I imagine roadside grit contains a lot of sodium in the winter. Can birds get hypertension? 😕

    January 18, 2021 at 9:33 am

    • From the Wildlife Society Bulletin, “Road Salts and Birds: An Assessment of the Risk with Particular Emphasis on Winter Finch Mortality” :

      “There have been many documented cases of bird mortality along roadsides where salt was applied. Herbivorous and granivorous species, especially, are attracted to salt, probably to satisfy a dietary need. Because mortality appears to be primarily a result of vehicle strikes, most authors have assumed that salt was only indirectly responsible for the deaths-a case of “fatal attraction” to busy salted roads. Repeated observations of apparent behavioral toxicity along roadsides, as well as new information on the toxicology of oral salt ingestion in birds, now suggest that salt toxicity per se is contributing to the vulnerability of small songbirds to road traffic and perhaps is a direct cause of mortality in some birds. The difficulty of retrieving bird carcasses and the low rate of reporting suggest that kills probably are more widespread and frequent than indicated by documented reports alone. Most known cases of songbird mortality have occurred within a group of birds collectively known as winter finches belonging to the subfamily Carduelinae. This may result from a higher probability of exposure for these species because of their diet and presence in the snow belt but also may reflect a greater ease of detecting mortality incidents in species forming large feeding flocks. The high attraction of salted roads for winter finches suggests that the roads’ ecological footprint is very large. We conclude that the importance of road salt as a mortality factor in these species long has been underestimated by wildlife managers and transport personnel.”

      January 18, 2021 at 2:53 pm

  3. Alice

    I was thinking something similar, Robyn. I know salt is bad for birds…chips, etc. I was thinking maybe rural roads don’t get salted. Definitely a reason not to use chemicals to get rid of weeds on the roadside.

    January 18, 2021 at 10:38 am

    • Robyn Deveney

      Alice – I’m in a pretty rural area in Maine, and our town applies salty sand to all the public roads here. My impression is that’s the norm throughout the state. It’s been the death of almost every vehicle I’ve ever owned!

      January 18, 2021 at 12:32 pm

      • Alice

        Maybe because you usually get way more snow than here, south of Boston? …except 2015, that is!

        January 18, 2021 at 2:45 pm

  4. John Jose

    Earlier this winter, on a day with snow covered roads in central Vermont, I came upon a couple of blue jays at a spot in the road where a plow truck inadvertently left a small but obvious patch of gravel and salt. I assume the blue jays were after the gravel for grit.

    January 18, 2021 at 12:54 pm

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