This phenomenon occurs when two sperm fertilise a single egg, resulting in a mixture of male and female cells in the developing embryo ...

No, this bird, as I sneaked closer, had a dark head, dark wings and tail and even a dark beak — whereas cardinal beaks, male or female, are yellowish. So, definitely a male robin and the ...

The smallest is the two-inch-long bee hummingbird. Everything about the anatomy of a bird reflects its ability to fly. The wings, for example, are shaped to create lift. The leading edge is ...