Although some very simple kinds of creatures, like bacteria, do simply make copies of themselves ... And if they're insects, or fish, or birds, or reptiles, they lay eggs. Us mammals are unusual ...

Birds do it, and bees do it. Indeed, researchers estimate that over 99.9% of eukaryotes reproduce sexually. What, then, are the true costs and benefits of sex? Yet again, this simple example ...

How Long Do Birds Live in Captivity ... and the same is true for tiny hummingbirds. Long-lived birds often reproduce very slowly. A pair of albatrosses or condors will raise no more than one ...

Birds build their nests out of ... getting the right nutrition before they can reproduce. So when [a bird] starts building a nest, they might do that together with their mate, or they might ...