The last carton of one dozen eggs that I bought, six of the eggs had double yolks. I usually get one double yolk out of every four or five cartons total. Six in one carton is stunning. For the record they were Jumbo eggs, brand name Penny Wise. Came from Meijer I think. Has anyone else noticed an increase in double yolks lately?
Here’s your culprit. Eggs are sized by weight; there isn’t someone at the beginning of the line with a ruler measuring eggs, so it makes sense that the ones with double yolks will be heavier and tend to fall into the “jumbo” category.
How often does a fertilized double yolker produce two chicks? Does that even happen?
I get that. I’m more curious about getting 6 in one carton vs getting 2 in four cartons.
The hen in question is on fertility pills. 
Were the 4 cartons also Jumbo sized?
Yes. I’m chalking it up to coincidence.
If you’re looking for a science-y answer, chicken eggs develop in the oviduct, which is a tube that runs from the ovaries to the “outside.” The oviduct has 5 regions through which the yolk travels on its development and way out.
When the ovary spits out a yolk, it first lands in the infundibulum. After about 20 minutes, it moves on to the magnum where it gains about half of its albumen, taking about 3 hours, then it goes to the isthmus where it gets most of the rest of the albumen and the inner and outer shell membranes form, taking about an hour. The next region is the uterus where the egg shell forms, taking about 19 hours. The last region is the the cloaca, which is essentially a single combined opening for urine, feces, and copulation.
Double yolks occur when the ovaries spit out a yolk sooner than the oviduct is ready for a new one (normally the rate is a little less than 1 per day). The ovary spits out a yolk, then quickly spits out another one, and the oviduct ends up with 2 yolks that then just go through the rest of the process together.
Young chickens that have just started laying eggs, or older ones at the end of their egg-laying “career” tend to produce more double-yolk eggs.
All or most of the eggs in any given carton are likely to have come from the same flock, which is likely to all be the same age, which greatly increases the chances of a run of double-yolk eggs every time the flock is “turned over.”
If you are getting store brand eggs, I’d venture a guess the store has a new egg purveyor.
When I was a kid, we got our eggs from a nearby chicken ranch. Double yolks were almost the norm. I remember one egg larger than the rest, with a somewhat lumpy appearance. It was a four-yolker.
And then there was the morning I went to fix a fried egg. When I broke the egg into the skillet, it looked like a miscarriage. I guess that one didn’t get candled. Of course, when I was a kid, the electronic egg grading and sorting was something that belonged in the Jetsons.
I walked away from the stove and forgot about breakfast. My long-suffering mother took care of the mess.
~VOW
I haven’t, but my eggs are from a different region than yours.
I’ve had triple yolk eggs from my uncle’s commercial hen houses. His eggs were sold to a hatchery. Jumbo eggs were culls that were given to family. Double yolks were pretty common. Triple were really special. Makes very good scrambled eggs.
Never gotten a triple yolk from grocery store eggs.
Interesting. All coming from the same flock makes sense I guess. The more yolks the merrier.
I’ve been having two eggs for breakfast every day for several years now, and don’t remember ever getting a double-yolk egg, but then these are large eggs, so that may be the reason.