I’ve long wanted to have the Bird Atlas 2007-11 maps available on my phone, when out in the field – and now I can (thanks to the BTO for letting me develop and deploy this through their channels, published 18/01/2016). It’s all offline, optimised to 100Mb space and contains maps not published in the book too. See details here
It uses an ExpandableListView and ListAdapter to open up available maps for each species, which then leads to an ExtendedViewPager and TouchImageView combination from Mike Ortiz, which makes the maps pinch zoomable with sensible constraints and actions. The ViewPager loads up to the max four maps at a time per species.
The user can also switch between BOU and Alphabetic species orders, and between the maps published in the book or all available species.