In this epic, beautifully written masterwork, Pulitzer Prize-winning author Isabel Wilkerson chronicles one of the great untold stories of American history: the decades-long migration of black citizens who fled the South for northern and western cities, in search of a better life. From 1915 to 1970, this exodus of almost six million people changed the face of America. She interviewed more than a thousand individuals, and gained access to new data...

Curious Pearl's friend is missing the birds that had nested in his yard. Where did they go? Pearl and her friend investigate, and in the process, they find out about migration. With augmented reality access to videos, readers will have an enhanced learning experience.

"Follows a single Christmas Island crab on its annual migration journey"--

A young emperor penguin makes a life-changing journey with his penguin pack, crossing the ice to spend a long dark winter on land.

Los factores explicativos de los volúmenes diferenciales de migrantes que se dirigen de una región a otra han sido considerados tradicionalmente en la literatura especializada como invariantes a través del tiempo. De otra parte, en la mayoría de los análisis cuantitativos a través de los cuales se intenta una explicación de diferenciales migratorios, se utilizan modelos lineales o aditivos, los cuales suponen que los factores actúan...