What bird is the symbol of peace?

1. A dove.
2. A pigeon.

(Are both OK? Is the answer only #1? What is the difference between 'dove' and 'pigeon'?)

1 is right.

Doves and pigeons are different species within the same family.

http://www.proz.com/forum/teaching_and_learning_languages/28738-dove_vs_pigeon_how_to_explain_the_difference.html

Both options are correct - a dove and a pigeon are both commonly associated with the symbol of peace.

The main difference between doves and pigeons is that they belong to the same family of birds, Columbidae, but are different species. Doves, also known as turtle doves or pigeons of peace, are typically smaller and more delicate-looking with a slender neck and pointed wings. They are often depicted as white or light gray with graceful and peaceful characteristics.

On the other hand, pigeons are generally larger and more robust-looking with a stout body and rounded wings. They come in a variety of colors and patterns, including gray, brown, black, and white. Pigeons are known for their adaptive nature and ability to thrive in urban environments.

Therefore, while both doves and pigeons are associated with peace, the image of a dove is more commonly used as a symbol of peace due to its elegant appearance and historical significance. In many cultures, doves have been associated with peace and harmony for centuries, often representing hope, love, and tranquility. However, it's worth noting that in different contexts and cultures, pigeons can also carry similar symbolism of peace and love.