I think there are individual differences though. My bantam Merle has been unwell when it's below freezing, even as a pullet.
You reminded me there's nuance to the idea that younger birds are better with the cold. The young Sussex are happy, but the Langshans, Brahmas, and Marans were unhappy their first winters.
Not saying it's a breed thing. The Langshans and Brahmas had roundworms the beginning of that first winter, which might've affected their reaction to cold that year. These days Unquestioned Head Hen Brahma Donna regularly pops out in the snow to survey her kingdom with Stilton.
To
@ManueB's point about individual birds, Frida the Langshan dislikes winter most of all. Their very first freeze, she was the bird who woke up with the lethargy and green poop that sent me running to the vet for the roundworm diagnosis.
Despite quick treatment and several winters in good health, Frida still pouts about the cold. Before the coop heaters, I'd occasionally bring her indoors to warm up. With the heaters, she's fine as long as she eats early and well, though she's the last to slink down the ramp in winter weather.
"I'm good here, thanks."
I do remember being impressed at the young Easter Eggers' winter mettle. Throwback to their first snow at 7 mos old, aww.
Meanwhile Marans Merle surveys the sideways snow and says "nope." He'll stay in the coop all day. Good plan, since his wattles almost bit the dust last year.
The high temperature this week was 34°F/1C, with the coldest night still ahead, exceptional for here. The biggest concern so far has been Andre's comb. A faint white band started to form on the back of it a few afternoons ago.
Last winter, we were able to save all but a few mm of one blade by whisking him indoors. Bachelor Andre liked the house, but On-Duty Andre wants none of it. I tried bringing him in the last hard freeze, and he crowed his head off and his comb started to droop. This time, I upgraded his heater instead, contorting myself in 25mph snow-wind with a [probably cold-induced] trippy ocular migraine to hang safety brackets.
According to the placement of poops last night, he approves of the heater, and his comb was better today. That's all the gratitude I need. I'm just worried about the 0/-18 temperatures in a few nights. He may lose a few blades this time
The Speckles just keep doing what they do. It snowed all day, unexpectedly. They couldn't find their feet in it by afternoon.