How is being endothermic both an advantage and disadvantage for birds?

How is being endothermic an advantage and a disadvantage for birds? It allows them with the appropriate body temperature needed to have a high metabolism and therefore enough energy for flying ... A disadvantage is that they have to eat large amounts of food to sustain these higher levels of energy.

Endothermic animals also require a food supply that is steady and reliable. During food shortages or in barren environments, endothermic animals may be less likely to survive than ectothermic animals, which can get by with less energy. The need for more food is one of the few drawbacks of endothermy