I was watching this video and the host said that the puffins dig over 80km of tunnels in the Farne Islands. Is that true? I couldn't find a source to confirm that number.
If that's the current number of tunnels at any one time, it can be right, it depends if they dig a new nest every year.
Farne islands has mostly horned puffins with rainbow beaks as opposed to tufted puffins which have an different beak, the former makes nest around 1 meter and the latter up to 2.75 meters,
Puffins lay one egg per year, there are 30-50,000 pairs of them on Farne islands, that's about 40km of new tunnels every year.
Every five years the trust carries out a larger audit, the last being in 2013, when puffin numbers on the islands were strong, at just under 40,000 pairs.
That was an increase on the 2008 figure when a stormy summer hit numbers hard from a high of more than 50,000 down to 36,000 breeding pairs.