The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Shearwater Marketing Group:
Created by the Chesapeake Bay Trust, this interactive field guide includes ALL the wild animals and plants of the Chesapeake Bay and its watershed. For novices and experts alike, the Chesapeake Bay Field Guide provides localized wildlife information about the birds, mammals, reptiles and amphibians, butterflies, trees, and seashore creatures you'll find around the Bay. It's comprehensive-- all native birds and animals are included, along with photos, in-depth descriptions, audio, field marks and more. Users can also search for Endangered Species or Poisonous/Dangerous species.