There are a LOT of reasons that you can have a stoppage, so it will take some investigative work.
You don't mention the age of your hens...have they gone through their molt? Most breeds lay well for the first 12 to 18 months, then will molt, depending upon the time they began to lay.The pile of feathers from the Australorp may indicate a molt (a bird's natural replacing of feathers that stops laying while she replenishes her body).
Also, shorten daylight will cause a dramatic slow down in laying...but generally you would have seen that reduction beginning in October with pick up beginning about now. BUT an abrupt change in weather pattern can trigger a molt if it has been warmer sunnier then suddenly turned dark and cold. Only a couple of days of that can trigger a molt and laying stoppage.
Ditto with changing lighting pattern...if you were lighting the coop at night to continue winter egg laying and the light bulb burned out and you didn't replace it immediately...that can trigger a molt and stoppage.
Another potential cause, for the Australorp, is broodiness, which it is about that time of the year for many to consider brooding (high season being April through June). Has she plucked her breast feathers? Is she staying in the nest? When one hen goes broody, often others will as well. Australorps are a breed that is known for going broody.
I doubt it is mice that are stealing the eggs as typically they are not big enough to cart an egg away, and they make a mess when they eat them in the nest. Look for a few shell pieces which would be left behind to see if that may be where they are going.
Do you have the possibility of snakes? Although during winter, snakes generally are hibernating. What about digger squirrels? They can clean a nest out too.
Another thing to look for is disease...often the first sign of a viral disease is the birds have stopped laying. Is anyone sniffing, snicking, sneezing? Looking a little rumpled? A mild case of Infectious Bronchitis can present first with these mild, hardly noticeable symptoms, and stoppage of laying, especially if the stoppage was preceded with odd egg coloring, ie a normally brown egg layer lays paler tint eggs, typically with a sandy or wrinkled appearance.
Stresses in the flock, as the other poster suggested, can be a factor. Not only predators, but change in ranging ability, feed and water.
Breeds matter too...some breeds are seasonal layers, especially the game types and specialty types, who may not lay during deep winter.
Good luck in figuring out your cause. Hopefully I've given you some ideas to track down.
Lady of McCamley
