The key to Heaven may have been hung on a nail, but church signs are good to perch on.

 Okay, it's a fact that all god fearing birds are very keen to please Oscar, God of all Birds, but within this devotion to a single bird there are different factions. For example, seagulls are known by other birds as Presbyterians - a term stolen from one form of human church.

Okay, to be honest, you'd be hard pressed to find a single bird who would understand that thing about the nail. Their English is pretty basic and usually limited to individual words. Their interpretation of 'Presbyterian' would probably be something like, "A comfortable sign." It is said by birds that most Presbyterian signs are pretty comfortable, though it is seagulls who have made them their own. 

As you know, birds don't really sit on signs, they perch - when a bird alights or rests on something.

Kevin Sparrow was not the most religious of birds and considered himself a bit of an agnostic, but he was drawn to the human Catholic Church because of its communion hosts. 

At the top of Tory Street in Wellington, in the 1960s, there was a school for boys. Tory Street led you into the back of the school. There was a boy that birds, especially sparrows, learnt to watch out for.

This third former was just learning to deal in communion hosts. He seemed to give them to other boys in exchange for money. Nothing lasts forever* and, when hosts got past the use by date, this boy would dump them in the nearest gutter in Tory Street. He did this while everyone else was in class. Birds reported hearing the phrase, "Father, can I go to the toilet?" They surmised that the sentence meant something like, "I'll just get rid of some old hosts."

Kevin and his mates were waiting.

 So, in an act of deceit, this boy from 3P was actually supplying a lifeline to sparrows. All Kevin's mates could vouch for that - Bill Sparrow, Cindy Sparrow, Caesar Sparrow, Paola Sparrow, to name a few. Kevin and his friends were always careful to leave a couple of hosts for Oscar, God of all Birds. They'd never actually seen him but, for many sparrows, their faith was strong.

The key to Avery was sitting beneath
a communion host.

* Except Oscar, God of all Birds.