Snakes are carnivorous reptiles which mean that snakes eat animals and not vegetables. There is no vegetarian snake species – all snakes eat meat. The amount of food they will eat and the size of their prey will depend largely on their size: larger snakes eat larger animals, while smaller snakes eat smaller animals, insects or bugs. Many snakes will eat eggs and birds they find in nests while looking for food. Large snakes such as anaconda or boa will eat large animals such as a pig. Certain snake species such as king cobra eat other snake species (this is why they are called king – for the fact that they are king to other snake species and can eat them).
How snakes kill their prey can put them in two large groups. One group of snakes kills their prey with venom (venomous snakes) and then eats them. Venom destroys cells in the prey's body, which is helpful not just for killing the prey but also for helping the snake to easily digest it. On the other hand, there is a group of snakes that kills prey by constricting it – squeezing it to death. This is really one of the most impressive adaptations of snakes because there is basically no other animal species that can swallow their entire prey and then entirely digest it. Snakes are capable of that thanks to the fact that they can completely unhinge their jaws and allow passage of such large prey. So, after the prey has been suffocated, the snake will swallow it and spend days, weeks and sometimes even months digesting it. At the end of the digesting process, the snake will vomit undigested bones, feathers, etc. that it couldn't process.
Snakes that eat eggs and birds are usually smaller snake species. They need less food than larger snake species, but it is important to say that snakes generally need less food than mammals. The reason for this is that snakes are cold-blooded animals, which means that they need much less energy to maintain a certain body temperature. In percents, snakes need 10% of the energy (i.e. food) that warm-blooded mammals of approximately equal size need for the mentioned reason. Snakes will adapt their body temperature to the temperature of their surroundings, so they can spend almost an entire winter in hibernation – at least those species that live in colder areas. In this period they definitely need very little food.
For more information about whether snakes eat birds, go to my Snake Removal - How to Get Rid of Snakes home page.