My 3 oh so tame Muscovy have been stubborn about spending nites in their coop as much as I try to get 'em to. A few evenings ago they ignored me and their snacks while floating 10ft from shore. That nite the wind blew rain & sleet, low was 11f degrees. The next am they looked haggered. 1 was shivering and another had frozen ice around her neck. Next nite, (6 degrees) they walked right into their pen with deep straw and after snacking, into their doghouse (where they were raised). It's somewhat wind protected with strawbales, and I've buried a 13-watt pet warmer under their straw. They looked so much happier next am and now they just swim over and walk right in. They seem to be comfortable outside to 15-20f or around 25-30 if windy. These are young 5 & 1/2 month olds. The cold was their catalyst to accept the coop.
[So much the better if you've power out at your coop. The lithium chemistry may not work below 14f; however, the batts generate some heat and if you place the power station in a plastic container, only slightly larger, it'll warm itself and provide power down to -10 or -20']
I use a 'Jackery 240' battery portable power station to power the 13 watt K & H warmer. It's actually drawing 14 watts but still warms for more/less 15hrs over nite. The warmth is slight but negates the ground chill. [In practice the J240 provides 216 watt hrs.] Their Ador2 Turkey door opens 30 min before sunrise and they are out and about in a minute.
https://www.amazon.com/PET-PRODUCTS-Warmer-Gray-Large/dp/B07RBBWJ7N/ref=sr_1_5?crid=17FBXM0UXJKU9&keywords=B+&+H+pet+warmer&qid=1705689577&sprefix=b+&+h+pet+warmer,aps,778&sr=8-5&th=1 and
https://www.amazon.com/Jackery-Portable-Power-Station-Generator/dp/B07D29QNMJ/ref=sr_1_3?crid=1XYZML6FRBSIE&keywords=jackery+240+power+station&qid=1705690823&sprefix=jackery+240,aps,184&sr=8-3&th=1
These Muscovy are fussy yet happy and wonderful companions. If I could just get 'em to eat peas.