Candling Duck Eggs

IncubatedEggsAfter our small coyote duck massacre, I came to realize I have no drakes left. I had winnowed down to two drakes, because too many aggressive breeders are hard on the ladies. Both of them came up missing. I want to always have fertilized eggs so I can breed more ducks from time to time, so a new boy duck is needed. If necessary, I’ll buy one. But for now, I stuck some eggs in the incubator in hopes that I might hatch a male for free. It would be good to increase the flock a little too, I like to keep at least a dozen ducks for laying.

I had one dozen duck eggs in the refrigerator, meant for eating. I pulled them out and warmed them up to room temperature for a day before putting them in the incubator. This practice is dodgy- usually the cold temperatures in the refrigerator will render the eggs unviable. But interestingly, nine of them have started to grow. Today is day seven, and I’ve candled all the eggs to cull any that weren’t fertile or that perished in the first week.

I saved an additional nine eggs laid in the week after the massacre. Laying was down, due to the birds’ stress level. In theory, female ducks who are bred should have about a week’s worth of fertilized eggs in them after a breeding event. In today’s candling, I found that three were not fertile, two had “blood rings,” meaning the embryo had started to grow, but then perished. Four were good.

So, I have thirteen growing eggs in the incubator. I’m groaning over trying to incubate duck eggs in this thing again, because I’ve had very low hatch rates, despite trying all sorts of different things to improve the success. This time, I’m not using the egg turner, as I suspect it puts the big duck eggs too close to the heating elements. That means hand-turning them three times a day. I admit, I’m not perfect at remembering to do this! I’m not putting any extra water source in there for humidity, the hygrometer indicates humidity is at about 65%, just from our normal Northwest air, which is about right, so I’m sticking with that!

When I candle eggs, I sometimes have a hard time knowing for sure what I’m seeing. To candle, I just use a regular “Mag” flashlight, and cup my hand around the top of the light and the bottom of the egg to control the light beam so I can see. I think this works as well as any fancy device might. Sometimes it’s obvious what I’m looking at, but other times the duck egg shells are so thick and full of surface irregularities that the interior is hard to visualize fully.

Here is an egg that is really obviously a good one, you can see the little embryo blob in the middle, and all of the blood vessels radiating out from that. At the top is the air cell, and the bottom you can see bright light shining through the “white” part of the egg interior. The yolk seems to start to change consistency at this stage, the whole side of the egg where the baby is forming will be dark-colored and shadowy, and won’t shift when the egg is turned.


“Blood rings” are standard indicators of embryo death, but I find that sometimes, it can be hard to differentiate them from live embryo growth, which also has a sort of oval ring at the perimeter of the spider-web of vasculature. Books always just show a drawing of what it looks like, which is a poor substitute for seeing the real thing. The big difference is the blood ring is small, and pretty round, with nothing inside the circle; where as live vasculature will spread over much more of the egg; and will always have that little embryo blob in the middle.

Today I saw a really good example of a blood ring (the “X” on the outside of the egg is just a pencil mark for me, to help with turning the eggs):


I cracked it open, and the blood ring shows up well here too. Embryo deaths in the first week can be caused by all sorts of things- rough handling or temperature irregularities in the incubator. Or sometimes, it’s just a bad egg.


31 thoughts on “Candling Duck Eggs

  1. Josh says:

    Like your comments about incubating duck eggs. I am trying it for the first time and we have the same incubator. I took out my turner as well. My eggs have been in about 4-5 days and I see a small round blob in the middle of the egg. Does this mean the embryo died? How did your efforts pan out? Josh

    • workingcollies says:

      Josh, the blob is good! In a few more days you’ll be able to see the web of blood vessels branching out from the blob, and then you’ll know things are cooking along. I’m still undecided on whether the turner helps or hurts. I do get better yields with chicken eggs, though still not spectacular. I believe I may have the crested gene in my duck population, and that may be contributing to the late perishing problem I see. I think ultimately maybe this incubator design is just too low tech to give consistent results, unless maybe it’s inside a climate controlled room?

  2. andrea says:

    Hi, I like your blog and the clear pictures of candling eggs. I gathered eggs from my friend’s ducks (2 ducks and a drake) hoping we could cook with them because the ducks aren’t broody. They have been in the fridge. I see a blood ring, and they sink in water because they are fresh. Are they OK to eat? Or am I killing little duck embryos?

    • workingcollies says:

      Hi Andrea- well, I’m no Health District official, but my guess is that if there is a true blood ring, then something incubated the eggs for a while to cause the embryos to grow, but then they perished shortly thereafter. So, you wouldn’t be killing the embryos if they are already dead (and generally after refrigeration, they are non-viable anyway, tho it is possible for some to survive the cold temps and still hatch later if incubated). If the eggs were incubated for a while, that means they weren’t always held at refrigerated temps though, and possibly are full of bacteria that killed the embryo. So, maybe not worth the risk of eating them? 🙂 That said, there are cultures that enjoy eating duck eggs which are quite far along in the incubation period- I think up to 3 out of the 4 weeks, so the little duck in there is quite mature. But I think they brine them, so presumably that would kill bacteria. But if you think they were taken straight from the ducks and put into the fridge, then I’m guessing you’re not seeing an embryo or blood ring, maybe just seeing the outline of the yolk and they are fine?

  3. andrea says:

    Thanks Michelle. I am not experienced with candling or with ducks, so I can’t say for sure if they’ve been incubated or what I’m looking at. I hard boiled one tho. I think my friends go in the ducks’ pen several times a day (there are pet goats in there that get lots of attention) and it would be hard not to notice an egg. They gather any they find and put them in the fridge.

    I don’t know anything about ducks but the drake is white and looks like a Pekin and the girls are a pretty dark greenish brown. Whether they are the same variety or not, I’m pretty sure the drake is fertilizing eggs 🙂 I hate for them to go to waste if the ducks won’t sit on them, and I won’t buy eggs at the store. I guess I could cook them for the dog if their safety is questionable for my family.

  4. Michelle says:

    Andrea, I bet they are fine, but of course, everyone has to assess their own threshold of risk and safety. 😛 There is always “thorough cooking” versus doing over-easy or soft-boiling, in theory, that should destroy any bacteria typically found in eggs. What I do when I find “mystery eggs” in the yard is crack them into their own bowl, and use my nose to decide if I think they are bad. Rotten egg smell is pretty distinctive. But that’s just me!

  5. Chrisssss says:

    Hi I have 8 duck eggs right now now there is one with the small blob and veins coming out but it does seem to have a ring around it. Now above it. Says the blood ring has nothing inside it. So could I be mistaking this or could it be that it was doing good blob and veins then died and got the blood ring once the embryo died?

    • workingcollies says:

      Chrisssss, I think the blood ring is the result of an embryo that was doing well, but then perished, and all the blood that was in the vasculature (for whatever reason) flows to a ring in the extremity- so you usually stop seeing the “spider web” of veins once that happens. If the spider web is still there, it’s normal to also see some kind of ring shape around them, though I usually find that it’s oval, whereas blood rings are more circular. If in doubt, let it keep incubating, you’ll know in a couple more weeks if the egg is full of baby that it was ok, otherwise its appearance won’t change much other than maybe getting murky. Good luck!

  6. Aubrie says:

    wow that is amazing, so the eggs were alreadt fertilized before they were put into the fridge? i kinda feel the need to go in my fridge and try it just for fun

    • Michelle Canfield says:

      Aubrie, yes, if the hens are with males, then their eggs are almost always fertile. But eggs from the store aren’t- those chickens don’t live with roosters… Normally you’re not supposed to refrigerate eggs that you plan to hatch, because the cold can kill some of the embryos. But a lot of them do survive the cool temperatures and will still hatch.

  7. andrea says:

    So far what I’ve learned about ducks includes that they like to live with other ducks and they like a mixed-gender flock. So usually if you get duck eggs they are fertile. Am I right, duck owners? I’m no duck expert 🙂 My friend has ducks and the females lay eggs, but she doesn’t want to hatch another generation of ducks so she gathers the eggs every morning and puts them in the fridge. They will be in there until we cook them so never get a chance to develop. I didn’t think it would work so I never tried. Same with the chicken eggs; they have roosters but chill the fresh eggs before they have a chance to start developing an embryo. I have seen eggs at the store marked fertile on occasion. If you get eggs from a store, that might be a good sign that the chickens live in good conditions with a little elbow room because I don’t think you’d find roosters in battery cages and if you did there’s no way they’d be able to fertilize eggs. It never occurred to me they could hatch if from the store because I thought they’d have been in cold storage for too long.

    How long can they stay cold and suspend the process of developing before they can be incubated and resume turning into a chick or ducky?

  8. Michelle Canfield says:

    Andrea, definitely ducks are very “flock-ey” and find comfort in their social group, tending to hang out together and gather tightly together in times of danger. I have noticed with my ducks that they segregate based on their raising groups, and don’t “mix” much. So their preference for company seems to be more related to whom they grew up with than gender. All female groups seem pretty happy to me.

    I would imagine you’re right that most eggs obtained from small farms happen to be fertilized, since most small farms probably keep males around to produce the next generation. And if you don’t have a lot of birds, then it doesn’t make sense to separate out the males and maintain two flocks. But males aren’t all delight- they are very aggressive maters, and I find the females mostly HATE this aspect. Especially if you have a low female-to-male ratio, the females get mated way too much, and can even get killed from being crushed, suffocated or just over-stressed. So I think that’s why most larger farms do not mix the sexes, because the hens probably lay more consistently, survive better, and stay healthier without that constant hassling from the men. And larger farms probably separate out breeding operations from laying operations, or don’t even do both, as the goals and infrastructure required are different.

    As far as egg embryos- so when they are laid, they are sort of in “stasis.” At regular air temperature, they don’t start developing, they wait. So if the hen gets on and off the nest a lot while she’s producing a clutch over a week or two, none of the embryos are growing yet, because she is letting them cool down between settings. It isn’t until the hen starts setting in earnest, where she stays on the nest almost 24/7, that the embryos kick into growth mode from the temperature cue. This is nature’s way of ensuring that the babies all hatch at the same time (not all birds work this way, but a lot of them do).

    Egg embryos are therefor pretty temperature sensitive, and can perish if they get too cold or too hot at any time during this “stasis” period or during growth. Humidity also affects them. And, the longer the time span between laying and when they go into an incubation temperature, the lower the hatching percentage. So putting them in the fridge, especially for days or weeks, will kill some, and damage others enough that they may not recover and hatch normally, even if they are put into correct conditions to hatch. But some of them are robust enough to survive this insult. A friend who is a zookeeper said they once tried freezing swallow eggs & putting them back into the nests, to discourage endless laying and prevent reproduction. And by golly if some of those frozen eggs didn’t hatch!

    So, it can happen even when it shouldn’t. Definitely the hatching percentage will drop for any batch of eggs that hasn’t been carefully temperature and climate controlled, or has sat too long before incubation- the more insulting the conditions, the lower the hatch. And some of the babies will be health-compromised, causing them to die during hatching, so it’s definitely not recommended to try to hatch eggs that have been chilled. I only did it this time because I needed those eggs after a lot of my adults had been killed.

  9. Chris says:

    Hi, I have had 20 muscovy duck eggs in the fridge and diced to put them in my incubator. I have noticed wen im candling them there is a black sack in the egg does that mean the egg is fertile?

    • Michelle Canfield says:

      Chris, I’m not sure, I’ve never seen black spots inside of eggs. I suppose it could be the growing baby, and it’s just dark-looking due to the egg surface influencing the appearance of the internal structures. Or it could be “bad” bacteria. I suppose all you can do is wait and see!

  10. Timmy says:

    Hi all I have just candled my egg’s and one of the egg’s has a large dark “thing” growing inside of it and the other has a “blood-ring” but I am not discarding any as i have had blood ring egg’s before, well what looked like blood ring’s and 5 day’s later when I candled them, the embryo was growing, what do i do this time ?

    • Michelle Canfield says:

      Timmy, I definitely think it’s worth leaving them in there if there is any doubt at all- though there is a small risk of bad/rotten eggs exploding and contaminating the rest of the eggs, I think that usually doesn’t happen until later. Usually at 10 or 15 days you can really tell for sure, and toss any eggs which are totally “open.”

  11. Tara says:

    Question!! I have a duck egg i have been incubating with a heating pad cushion and have been adding water. It was clearly fertile on day 7 and had veins and an embryo. However, the temp somehow peeked during the night and on day 11, there were no more veins present and I don’t know how to tell if he has passed away… please help what should i look for and does it always move in the egg bc there is no movement either :'(

    • Michelle Canfield says:

      Tara, hmmm. Usually unless you can clearly see a blood ring, where all of the blood has traveled out of the vessels and into a singular, circular ring, it may still be worth waiting to see if it hatches. Eggs are harder to candle once they are older than 7 days, because the vasculature starts to fill the egg, and you can no longer really see what’s going on in there.

      Though incubating with heating pads, lamps, and even the inexpensive “foam cooler” methods does tend to produce more losses because of the inexact temperature control; eggs can be surprisingly robust and survive some bobbles. Getting a little too warm usually just means they hatch sooner, or will be weak at hatching and may need some help.

      The baby doesn’t really move around in the egg until the last couple of days. The baby is passive during growth and relies on his mother to rotate his eggs multiple times a day. You should turn the egg 2+ times a day, but in the last 2 days, stop turning. Then the mature baby will twist himself around inside the egg to get correctly oriented for the hatch.

  12. jillnbob says:

    New to ducks this year, have had many, many chickens with natural hatches (unfortunatey a large percentage of boys who were dispatched to the chop shop). Have 12 Pekin girls and one definite Pekin drake, might have another altho they were supposed to be all females, but of course as they “come of age” the girls mate with girls and so forth and so on, have a real duck train in the pool every day. 22 weeks now, they started laying and co-mating at 18 weeks 🙂 :), all are laying now, and the drake is VERY busy. Anyway, have a big girl who is determined to brood, and letting her. Candled today, some look promising, but probably too early to tell for some (few days to a week or so). She’s very attentive to her nest in the dog crate, always primping it and turning her eggs, eats, drinks, right back to the nest. She gets her free range time every day along with the others,they all live together and seems to be the leader as she is the 1st in at dusk, all follow, right to the nest she goes. I see that a lot on here incubate, what do you think my chances are of her hatching just a few on her own? Would like to see nature do its thing, and won’t be too upset if it doesn’t happen, but she seems to be a natural born mom, even with the others. Should I separate her and her clutch at a certain point? If she does hatch, are the others jealous like chickens, will they hurt the babes? She still lets some of her sisters go to her nest and deposit, and tends to most of the eggs, pushes one out here and there. If she abandons any hatchlings, will certainly tend to them, but in your experience, and her being 1st time mom, whaddya think?

    • Michelle Canfield says:

      jillnbob- I bet she will be fine. I haven’t had Pekins before, so don’t know what kind of mothers they make. I have had some ducks look like they are doing a really good job on the eggs, only to fall apart when the babies start hatching, getting all panicked and leaving the nest. But the only way to know is to let them try and see how they do. I usually lock up the mother & babies in a pen after they hatch. Just because I don’t think they are always able to defend them against other birds in your flock, or predatory birds. Good luck!

  13. I am featherfriender on says:

    @jillnbob …Wow,Pekins rarely go broody…how did it turn out? If she was successful,:are the duckings managing under her care without being hurt by the rest of the flock?

  14. Cathryn says:

    We have Peking ducks and use the eggs for baking. We keep them in the fridge sometimes for quite a while. Once in a while we have a rotten one but the other day when I was cracking some open for a cake, every one had a partially developed duckling inside, some even with eyes and feet. None of them had been in the duck yard more than a few days, but every one I opened had been developing for some time in the fridge.

    • Michelle Canfield says:

      Wow, Cathryn, that’s not supposed to happen- they must not have read the literature! :-0 It’s crazy how animals don’t follow the rules sometimes!

  15. Nicolle says:

    Hi, i have been incubating my duck eggs for almost 7 days now, (the site i got them off of said only 80% of them would be fertile but all of my 11 duck eggs have veins!! 🙂 ) Anyway, i am not sure if i have been turning them right, i looked it up and nothing tells me specifically how to turn them. I know i have to turn them 3-7 times a day but do i turn them all the way around, half way or some other way? I just don’t want to something to happen to my eggs because of the way i am turning them.

    • Michelle Canfield says:

      Nicolle- if you see the way a mama duck turns them, she usually has the eggs laying on their sides, and she just nudges them with her bill to “spin” them a bit, and she fiddles with them multiple times per day. Randomness is fine, the idea is mostly to prevent the yolk from “sticking” to one side if it sits in one position too long. Some say to use a pencil to mark “1, 2, 3 and 4” on each “quadrant” of the egg; then just rotate them 1/4 turn each time you turn them, cycling through all 4 positions. Then, I think you are supposed to stop a couple of days before the hatch, because by then, the duckling is trying to twist around to get oriented to chip his way outta there, so if you keep moving him, it’s more work for him to keep re-orienting. Tho, honestly, I wonder of mama ducks know this, I suspect they may fiddle with them all the way up until they hear them cheeping and trying to hatch.

  16. Rick and Susie Walker says:

    Hi, Michelle, we are new to duck raising and have really enjoyed reading the questions and answers here. We live outside Olympia, have some ducks whose eggs we will start to incubate next week, and some new ducklings due in at end of next month. Really fun for us.
    Thanks for your information.
    Rick and Susie

  17. Brie says:

    I am taking care of 10 mallard duck eggs and there is little grey spots in the egg. What does that mean?!? They have heartbeats and they have feathers when you candle them so at least they are alive, but I don’t know what little grey spots inside the eggs mean.

Leave a Reply

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