People always longed to know what the future holds, either out of curiosity or mainly in order to anticipate unseen dangers. All ancient civilizations - and even some cultures of today - used all kind of methods to predict the future. One of them is "divination", i.e., reading in nature or in trivial events signs and indications for what the future awaits. In Hilkhot 'aboda zara 11:4 Maimonides explains that the Tora condemns this practice and brings some illustrations of divination: "For example, those who say: Since a piece of bread fell out of my mouth, or my staff fell from my hand, I will not travel to this place". Or, "Since a fox [today we would say: a black cat] passed on my right side, I will not go out of my house, since if I were to go out, I would encounter a bad person". In our days we call this practices "superstitions". But because superstitions include many different categories, we should see these cases (=reading signs) as "divination".
Ancient civilizations had seers and wizards who, for example, would read signs in the internal organs of slaughtered animals or would wait in the forest to listen the chirping of the birds. The bird's songs were taken as messages from the gods or magic spirits. Maimonides continues: "Similarly, [this category includes] those who hear the chirping of a bird and say: This will happen or this will not happen; it is beneficial to do this or it is detrimental to do this."
The idea behind "divination" is that the gods are sending a message, warning against unpredicted dangers. We Jews do not believe that nature embodies divine attributes. We Jews believe that God's instructions for our life are explicitly expressed in the Tora, not hidden in natural phenomena. The practice of divination is a desperate attempt to escape the responsibility to choose, probably out of fear of unpredictable outcomes. Connecting the dots between the chirping of the birds etc., and what the future awaits, is the product of a rich imagination and self-deception. We Jews do not read imaginary signs in nature. We read God's will in the Tora, and exercise our freedom of choice.
Some present day politicians believe that birds are still carrying messages from the spirits. See this