"A serious writer is not to be confounded with a solemn writer. A serious writer may be a hawk or a buzzard or even a popinjay, but a solemn writer is always a bloody owl"

In this quote, Ernest Hemingway is making a distinction between a severe author and a solemn writer. A major author is somebody who is enthusiastic and dedicated to their craft, regardless of their personality or style. They might be serious, funny, and even flamboyant. On the other hand, a solemn writer is someone who is extremely serious and takes themselves too seriously. They are often dull and uninspiring, like an owl. Hemingway is emphasizing the value of being major about writing, however likewise having a sense of humor and creativity. He is encouraging writers to be enthusiastic and dedicated to their craft, but also to have a good time and be open to originalities.