If they needed to phone each other they would only need two digit phone numbers.
There's still a week to go to choose NZ's Bird of the Year. You can choose up to five birds and I'd ask you to spare a thought for the little fairy tern.
They're NZ's rarest bird and with only 35 adults left in the world, they must know each other by name.
Vote here:
https://www.birdoftheyear.org.nz/
Voting has opened for bird of the year, and as @craftygardennz says, "This year I'm Team Fairy Tern". There are only 35 adults left and their plight deserves publicity.
T E A M F A I R Y T E R N !
Look at this little fluffball. The fairy tern is NZ's most endangered bird with fewer than 35 adult birds remaining. RNZ looks at efforts to save these little cuties.
Fairy Terns lay their eggs on a branch that is somewhat level and perhaps in a bit of a depression. No nest whatsoever. As a result the first thing out of hatching egg are the feet, which then clamp on for dear life.
Future Sprog
Bob LeFridge 
rusty
ARW