Apple tree, growing leaf buds falling off - why?

Mr. Vine Eye

On Friday I noticed that my 2nd year espalier Apple tree was showing new growth from the leaf buds. There was a good half inch shoot growing from the central leader and the other buds lower down the stem and the first tier lateral branches were showing green growth too.

I went to look yesterday and that shoot from the leader was no longer there, it had fallen out. Same with the two buds below (destined to be the next tier branches)

Leaving the buds looking like empty pits, like gums after the tooth has been removed

I had a little panic. But then I remembered that this exact same thing happened last year in early spring. Then within a couple of weeks the buds started to regrow and all was well.

so I'm hoping the same thing will happen again.

Does anyone know why this happens? Weather was mild over the last few days.
Ive also got a crabapple tree and that hasn't done this, the buds just opened and continued growing.

Mr. Vine Eye

This was Friday







This was last year when the shoots started regrowing 

pansyface

Bullfinches.

Mr. Vine Eye

I thought it could be birds, but then why would they have only gone for the top few buds and left all the rest - and why only this tree - have 4 other fruit trees and they haven't been touched. I found the shoot at the base of the tree so it hadn't been eaten.

Also we have so many cats around here that I've rarely seen a bird in our garden.

pansyface

The term “bird brain” wasn’t coined for nothing.

Mr. Vine Eye

They are regrowing now by the looks of it!

Pete.8

My neighbour has 3 amelanchiers and I have one.
Every spring as the buds swell, pigeons arrive on one of my nighbour's amelanchiers and remove all the buds from the top 1/3 within a couple of days. They don't touch the other two or mine which are both close by.