Freezing is not the only threat. The functioning of cells depends on proteins that only work effectively within certain temperature ranges. Ectotherms tend to h

Freezing is not the only threat. The functioning of cells depends on proteins that only work effectively within certain temperature ranges. Ectotherms tend to have multiple different pathways for a given process that cover several different temperature ranges while endotherms don't. So, do birds have that? Do their feet still grow, heal, fight infections when they're cold or do they depend on time spent with their feet warm?