Winter laying is something I think might have been discussed here before, but there is really no clear definition and many people think they will lay in winter like other hens lay in spring or summer. This is the only definition I could find for a "winter layer" - “jump to” 68 at the bottom of the page
http://babel.hathitrust.org/cgi/pt?id=coo.31924073887782
William Powell-Owen was a legend in poultry during the early part of last century Here is a quotation from his book The ABC of Breeding Poultry , 1919 : https://archive.org/details/cu31924003045261
" SUMMER AND WINTER EGGS.
In the summer months people argue that eggs are not worth
troubling about as they are so low in price. These cheap siunmer
eggs should be preserved and sold at remunerative prices in the
winter as " preserveds " or used in the house whilst the new-laids
are sold in the winter. The winter egg is the thing we want and
yet how difficult it is to obtain. So many poultry-keepers will
have us believe. I^et us bear the following in mind and eggs
should be forthcoming when " eggs is eggs." Non-sitters should
be hatched in April, May and June and sitters or " heavy " breeds,
in February, March and April. The pullets should lay, with careful
handling, by the middle of October or beginning of November.
Those that lay earUer i.e., before they are fully matured should
be stopped. This can be done by not feeding on any stimulating
foods for a time and changing the pullets to fresh quarters. Do
not boast if your pullets lay at five months, this is unnatural and
harmful to them. Do not hatch late in the season ; separate the
sexes at an early age, allowing the pullets to have all available
space ; do not overcrowd ; push the youngsters on from the
beginning, not allowing them to look back. Pullets are but very
little creatures and need careful handling."
"Dr Pearl in his work considered any pullet which laid 30 eggs or more from November 1 to March 1 to be a good winter layer and a profitable bird to keep. in general, it may be said that a pullet which lays 50-60 eggs from November 1 to March 1 has a good chance to make a record of 200 eggs or better.”
Dr, Pearl and Oscar Smart had a somewhat competitive professional relationship in the poultry world. What Dr. Pearl espoused closely mirrors the brilliant work done by Oscar Smart ( Britain's foremost poultry biologist). of the same era as Dr. Pearl. Oscar Smart wrote a brilliant book called , " The Inheritance of Fecundity in Fowls." In it de describes his method for determining rate of lay during the winter months and using this info to determine quality of laying production...using this info to increase laying production in a flock breeding program. Here's the ebook,"
The inheritance of fecundity in fowls.
by Smart, Oscar.
Published 1921
http://babel.hathitrust.org/cgi/pt?id=coo.31924003164450;view=1up;seq=3
Oscar Smart died very young in 1919 in the midst of a brilliant career in poultry biology and genetics.
It was a great loss to the poultry world.
Best,
Karen