New Zealand's Biggest Year is an epic birding tale of how two friends become rivals and set out to break the all-time record for the most Aotearoa New Zealand bird species seen in one calendar year. Their rivalry results in more birds being spotted in a single year than ever before and two national records are broken. However, which of these two birders will take the title and become the all-time biggest year lister Aotearoa New Zealand has ever seen?

From the first day at the top of South Island to the sprint finish on the Chatham Islands, this is Harry Boorman's personal account of his epic, year-long adventure. Full of twists and turns, unexpected sightings, pandemics and trip cancellations, including the addition of a species (the Emus) to the official bird list on the very last day, Harry's story gradually unfolds to its nail-biting conclusion.