When should I turn a heat lamp on for my birds? Here where I live low was 45 at night should I have a heat lamp on? Cover up vents in coop? Or let them be till its closer to freezing. Im new to all this. Thanks.
Especially never limit ventilation.
Chickens die from bad air and heat but not from cold.
Chickens evolved from jungle fowl that ranged up into the Himalayan foothills. Since then, they've spread around the globe and were developed into breeds in all climates - with no heat.
I would be willing to bet that your breeds were developed in New England, England, Continental Europe or colder regions of Asia. What breeds do you have?
They aren't tropical cage birds, they're outdoor birds that can handle an incredible range of temperatures as long as they have good ventilation. The only reason for a coop is predator protection. Protection from rain is good too but not absolutely essential. They're pretty tough.
Chicken Canoe is right. People in Alaska don't heat their coops, and understand the need for ventilation. Here are a couple of very good articles by a Canadian member: