The ability to fly prevents birds from producing live young, as mammals do. To keep their weight down, birds lay each egg as soon as its formed. But once outside the body, the egg must be kept safe from predators and needs to maintain the correct body temperature. The Problems of Parenthood relates that with insatiable appetites to provide for and the need for unfailing vigilance, bringing up baby birds is a full-time job that requires very special skills. Some birds feed all their young equally, while others feed the biggest.
Some birds also take on helpers to help rear their young.
The Limits of Endurance shows that in the unending struggle for survival, changes and disasters wrought by both nature and man create new challenges that birds must constantly meet and overcome. Many not only survive, but breed in environments that other creatures cannot endure. Seeking Solutions with Hedrick Smith focuses on how several communities developed effective grassroots responses to local crime problems such as teen gangs, street crime, ethnic violence, and hate crimes. Accomplishing the feat 12 years before the better-known exploits of Lewis and Clark, Mackenzie was the first European to record a journey across North America. It was Mackenzie's account of his adventures, published in 1801, that inspired President Thomas Jefferson to commission the Lewis and Clark expedition.