It used to be that having a “bird brain” was an insult. Now, it’s practically a compliment! Turns out the brain of a bird, which is small enough to fit into a nut, is full of neurons. These animals are capable of complex cognition — they can solve problems, count, understand cause and effect, and even communicate in ways that resemble language. Jennifer Ackerman chronicles birds’ intelligence in her book, “The Genius of Birds.” She sits down with Alexander Taylor, an animal psychologist who’s been studying the Caledonian crow — a bird that creates tools and passes on those lessons to younger generations. Flora Lichtman, host of the Gimlet Media podcast “Every Little Thing,” moderates the conversation.