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 CleverMatrix Ltd:
Our Big Garden Birdwatch Log HD app is to help you record your results for the RSPB Big Garden Birdwatch on Saturday 29, or Sunday 30 January 2011. The RSPB Big Garden Birdwatch is the worlds biggest bird survey, occurring annually, attracting nearly half a million participants. The records from people counting birds in their gardens provides a vital snapshot of the UK's birds each winter. More than 6 million birds have been counted in the Big Garden Birdwatch and it has given some interesting insights into the populations of birds in Britain. So this January, help out the RSPB and discover which birds are really in your garden. All you need to do is spend an hour spying on the birds in your garden or local park and record the results easily using our app and then submit them online to the RSPB. All the results will then be collated in March and the data used to help them decide which birds they need to focus their conservation work towards.NOTE: The email functionality within this app is for your own personal use, please do not email your results to RSPB. Results should be entered on their website only.