The size of eggs. Age, breed, weight of the hen, diet, weather, stress, and environment (overcrowding) all contribute to the size of the egg. As hens mature, the egg size increases. I selected breeds known to be (a) good layers, and (b) winter hardy. Myrtle, whom I have had for three summers now, lays ENORMOUS eggs. Most of my hens lay large - x-large eggs. My younger hens lay medium to large eggs. The Plymouth Rock eggs are distinct from the others because they have thicker shells and tougher membranes. The eggs taste the same, but are harder to crack. And, although one of those Plymouth Rocks is the same age as Myrtle, Penny's eggs are noticeably smaller than Myrtle's eggs. (Myrtle has always been an over-achiever--she laid 2 eggs/day for the first month of her production way-back-when and often will lay a double-yolker--hence the name Fertile Myrtle).
When my hens are able to forage, the yolks are a deep yellow-orange. During the winter months, the yolks a a rich yellow, but not orange.
When it is extremely hot, egg production goes down, the same is true in the winter but that is related more to the number of hours of light / day. Hens need about 15 hours of light/day to complete the egg cycle. In the winter, the daylight hours are extended using lights (I usually start this the end of November). One can also slow down the maturation rate of chicks by reducing the number of hours of light or hastened the maturation rate by increasing the number of hours of light. If hens are broody (sitting on eggs) or molting (about every 18 months, but that depends on breed, etc.), they will stop laying eggs. While a momma hen is tending chicks, she will usually not lay eggs or will only lay one every 6-7 days.
The majority of my hens are either Lohmann's (a breed developed in Germany for egg production and for producing eggs consistently until about 3 years of age) or Red Schaffer's (a Canadian breed, also winter hardy and about the same re egg production as the Lohmann's) (I have 18 "red" hens). The Plymouth Rocks lay a smaller egg with a thicker shell (however, all hens produce the same amount of shell--but the larger the egg, the thinner the shell), the rest of the hens lay about the same size of egg (large). Sometimes I get a funny-shaped egg, but that's not really relevant. Eggs are graded according to weight, quality of yolk, and white. Here's a link to a pdf chart of egg weight (per carton and per egg) for each size:
http://curbstonevalley.com/wp-content/uploads/2010/09/eggsizes.jpg
I have always assumed that was "in shell" weight. Most recipes require a large egg. One can either weigh the egg or measure the egg in cups to do the conversion.
Eggs From A To Z - Size Equivalents
BTW, I don't think the chart at the bottom is to scale (at least not on my monitor). If it is, my hens lay eggs that exceed Jumbo size...maybe it is time I get out my scale and weigh eggs...
CarolPA, that is probably more than you ever wanted to know about egg size. Hope this answers some of your questions.
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