Bird seed surprise

Seed full of granary weevils, Sitophilus sp.

One of my responsibilities while house-sitting for my parents is keeping the bird feeders well-stocked. With the period of extremely cold temperatures (at least for this time of year – we’d be laughing come February) the feeders were a hive of activity, and the seed levels dropped steadily. The sunflower and thistle seed feeders were filled again without trouble, but when I dug the scoop into the bag of mixed seed, I noticed a sharp, distinctly mouldy smell. Peering closer, it looked like perhaps the peanuts had started to turn, and it was maybe spreading to the other seed, but I couldn’t really tell. It didn’t look really bad yet, so I stood there for a moment or two, holding the container in my hand, staring at the seed inside as I pondered whether it was still okay to put out for the birds (mould can be poisonous to birds once it’s progressed).

I finally decided better to be safe and not put the seed out, but while I was standing there contemplatively staring at the seeds, I noticed something else. Some movement. The seeds were starting to wiggle. And then…

Granary weevils, Sitophilus sp.

…from between them, out crawled a tiny beetle. And then another. And a third. And before I knew it, the top was crawling with a dozen or more little beetles. More accurately, little weevils, as I could clearly see the thin snouts protruding from the front of their heads. Weevils are sometimes also known as snout beetles because of this feature. There are some 60,000 species in the weevil superfamily, Curculionoidea. Most belong to the family Curculionidae, and about 2600 species from this family are found in North America. Most are herbivorous, and many are crop pests.

Granary weevil, Sitophilus sp.

Probably the interaction most people will have with weevils is the opening of a bag of something to discover an infestation of them. They are common outdoor bugs, but are generally small and inconspicuous unless they happen to land on your drink glass or some other coincidental meeting. However, they do occasionally make it home in bags of grain or seed products. There are three species, all in the genus Sitophilus, who are encountered this way, but they tend to be so similar in appearance that identification to species is best left to an expert with a microscope. They have food preferences, but there is a lot of overlap and they will opportunistically infest other sources when their preferred food isn’t readily available.

Granary weevil, Sitophilus sp.

The three species are Rice Weevil (Sitophilus oryzae), Granary Weevil (S. granarius), and Maize Weevil (S. zeamais), and their common names reflect their preferred food (here in North America, maize is more often called corn). They often come home in infested bags of bird seed (Granary and Maize weevils may prefer mixed seed, Rice Weevils are often found in sunflower), but will sometimes be found in packages of rice, beans, peanuts, or whole-grain cereals. I couldn’t tell which seeds specifically had been targeted in the package, although the amount of mould growing on the peanuts made me suspicious of them. I think that the decay of the seeds that the weevils had been feeding on, whichever ones they were, had lead to the mould.

Granary weevil, Sitophilus sp.

The life cycle of these weevils takes about a month to complete, and requires temperatures of a minimum of 17 oC (62 oF), but ideally 27 oC (80 oF) and above, and moderate to high humidity. The adult weevil lays their eggs on appropriate seed or grains which will become the food source for the developing larva. When the egg hatches, the larva tunnels into the grain and sets up shop inside. It takes about 3 days for an egg to hatch from laying, and then the larva may be in the grain for another 18 days, at which point it develops into a pupa. Once the adult emerges from the pupa, some 6 days later, it stays in the relative protection of the grain until its exoskeleton has completely hardened and matured, about 3-4 days.

Granary weevil, Sitophilus sp.

Because they spend most of their cycle inside the grain itself, it may be possible to be harbouring these little bugs in a stored product for a few weeks without even knowing they’re there. Generally speaking, the incidence of infestation is rare, and probably even if they are present the product is consumed before the eggs get a chance to develop and we’re never the wiser (consider it added protein). By the time the bugs reach adult, stage, however, consuming them or the secretions they produce can sometimes result in E. coli infections, depending on the weevil’s particular diet.

Granary weevils, Sitophilus sp.

I dumped a few out on a blank piece of white paper to try to get some uncluttered photos of individuals, but I had minimal luck. They were just too quick! I found that initially they would curl up their legs and play dead, for instance if I shook the paper to knock them all back to a central starting point. But moments later they’d unfold and start hustling across the paper. Interestingly, their direction of movement wasn’t random. They all moved with a purpose, and while their particular direction varied, it was always directly towards the edge of the paper. I thought perhaps they were trying to get away from the bright halogen that was hanging over the center of the paper to provide illumination for the photos.

None of them ever tried to fly, which I think perhaps rules out Rice Weevil, which is supposed to be winged and attracted to lights. The Granary Weevil has poorly developed wings and can’t fly, and is also not attracted to lights. On the other hand, Rice Weevils are reddish-brown and have 4 pale marks on their wing covers (Maize Weevils are similar), while Granary Weevils are reddish-brown to black and unmarked. Going by that, it looks like I have both in this group. So who knows! When I submitted the images to BugGuide.net, the person who identified them thought it safest just to leave them at genus.

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22 responses to “Bird seed surprise

  1. Creepy. Although, many bugs would totally enjoy the nummy little bits of extra wiggly protein! :)

  2. At least it was bird seed and not people food! Cool shots of the weevils. It is somewhat interesting that the word “tested” appears on the can.

    Tom

  3. I like the long noses on weevils, but don’t particularly care for assemblies of them.

  4. Rockin’ post! I was curious to know how you chose to dispose of the infested seed–always a dilemma when moldy peanuts are involved. I usually double-bag it and put it in the trash. In 40-plus years of bird feeding, I’ve had one suspected aflatoxin poisoning from some peanuts left out too long in the summer–two dead cardinals suddenly under the deck–distressing.

    Your thoroughness and high information content is admirable and much appreciated. Leckiepedia.

  5. I considered that, Lisa – if it weren’t for the mould, I would totally have put the seed out for the birds, knowing they’d enjoy the bugs!

    Somewhat ironic, eh, Tom? Fortunately, the can actually came full of cashews and is now serving a new life as a birdseed scoop, so the tested doesn’t apply to the bad seed.

    Fortunately, Lavenderbay, assemblies aren’t all that common!

    Thanks, Julie! We did the same as you, bundled it up in the trash. I’m glad to hear that it’s an uncommon occurrence for it to make it to the point where it affects birds. I have to agree that finding birds dead as a result of your well-meaning bird feeding would be rather distressing.

  6. Weevils are interesting little critters that seem to take over a kitchen readily. I used to keep bags of chicken feed and bird seed in my garage, but one infestation had hundreds of weevils in my kitchen so now those bags of grain get to stay on my back porch. So, in addition to the weevils, sometimes ants find the grain before the birds eat it all, and once in a while a squirrel tears into a bag.

  7. your articles are interesting and so useful for me. Thank you for sharing great information.

  8. I just opened up a bag of bird seed only to find the bag infested with these things! Creepy looking things, my birds aern’t bothered by them at all though.

  9. i poured a cup full of birdfood out onto a tray I have outside…..I usually just sprinkle it out into the grass, but since the tray, I got to notice the amount of weavils in the seed. Honestly, the seed I bought was chock full of corn. So, I presume is alot of birdseed. So, there’s probably a good chance that it is the maize weavil. I have a 15 lb bag of rice in a cupboard adjacent to the place I kept the birdseed (which will find a different home from now on)….and to my suprise and delight there were no weavils in my rice. :) Awesome thread!

  10. Pingback: Bugs in the birds seed! - Avian Avenue Parrot & Other Birds Message Board

  11. Thanks for this – just had an infestation in my apartment and it took me ages to work out what they were. My sister found a packet of bird seed in the cupboard that I forgot I had. One dustbin bag later and a good vacuum and hey presto – all gone!

  12. My husband bought a 20 lb of birdseed which was kept in a corner in the kitchen (Uh-Oh big mistake). Walked into the kitchen one day and little black bugs were going everywhere. I hate bugs! Called my pest control company and they came out and sprayed. Told me to call back if I still saw them in a couple of days. I will clean out my cabinets to see if they invested any food. Just looking in the cabinet, I haven’t seen any.

  13. Hubby kept (notice past tense) birdfood in waste bins by the front door, handy to fill up the feeders in the front yard. Ten years, no problems. However, last week I found a couple of wiggly worms about 10 cm. long going up the wall in the entry way. Two days later I found more….LOTS MORE. Turns out the entry way/dining room were loaded with the buggers. Bird seed out to the shed now, spray, smash and kill (no the dining room needs re-painting), and an afternoon gassing of the house (all pets outside). Now we find lots of dead larvae (no adults) and some still wiggling. After reading this I guess we gas again in 3 days. One good thing, we had dinner guests on Friday night and NO larvae dropped off the ceiling into the food…..though when we looked carefully Saturday, we were amazed that it didn’t happen! Guess we were just lucky. Nell n TN

  14. Thanks for the post. Kept finding these bugs over last two weeks in the house & could not identify them. Was one day away from calling exterminator. put a few on a piece of white paper to get a better look. Found images in this post & knew we had a match. We keep birdseed on shelf at top of cellar stairs…that was the source. birdseed is out & will never be back…half hour of cleaning & hopefully this is the last of the granary weevils or whatever they are…NASTY!

  15. -
    Great message!
    -
    BUT!—- DO BIRDS ‘DIE’! —OR ‘AVOID’ “ADULT” INFESTED’ SEED?
    -
    Thanks, Jim

  16. I am wondering what “Jim” asked. I have had meal moths (I think) in my parrot seed mix before and was told to freeze it and of course, the meal worms are good food. But these wee beasties? Are they edible (adult stage) for birds?
    I just noticed about 10 on my bird room window sill.
    Not sure how to kill them without hurting my parrots.

  17. Amazing post! Thank you so much! I had kept birdseed for my love bird in a bucket in my kitchen thinking nothing about bugs because the seed goes by so fast…but this past week I kept finding those little buggers crawling on my couch and everywhere around. I thought they were bed bugs or something at first but they didn’t really look like them. Then my brother went to scoop some bird seed out and found tons of them! Crawling around moving the seed which was kinda like a horror movie why they crawled out of the bucket on to the floor going everywhere! I never thought to check the birdseed. So again amazing post, thank you thank you thank you!

  18. YOU SAVED MY KITCHEN…and my sanity! I couldnt figure out what they were but after reading this, I knew I found my culprit! They were in a bag of yellow split peas I bought from the local discount store back in March. Thanks again for the post~ MOST helpful!!

  19. You are my total answer….thank you…great post

  20. Have a parrot and bought a bunch of by the pound seed…..infested….they returned the bags and found lots more in other bulk containers….finally got issue resolved…but the pet shop owner asked me if I ever found the answer to this to call him…can’t wait to call him next…thank you again

  21. I have a Parrot and I keep his cage in our Bathroom. I kept seeing these little bugs crawling on the floor, in the tub, on walls and in the Birds water. I buy the Birdseed from Walmart in the plastic containers with the lid. I never seen anything when I poured it in the bowl so I never thought about it but after seeing your post that’s what they are. So Glad I found this information because trying to figure out what they were was driving me crazy. And yes when they are crawling on the floor if you put your finger in front of them they do pull their legs in and play dead. Thank’s again!

  22. Thanks for this Post , I Found these Little Insects on my Bird’s Food…Thank God I Keep the Bird Food in a Plastic Container with a Lid that you have to Turn to Close … They Were all Over Inside the Container … Dumped the Bird Food Little by Little in the Toilet and Rinsed the Plastic Container and Put in a FRESH BOX of UNOPENED BIRD FOOD I Had… at Least I Don’t have to Worry about these Weevil Seed Bugs are Not Related to any Type of MITES!!

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