During a walk in Sutton Park, Birmingham, this morning, organised by the RSPB Walsall Local Group (of which I am a committee member, webmaster and speakers’ secretary — I multitask!) we observed what may be unusual Blue Tit (Cyanistes caeruleus) behaviour. A bird (or possibly a pair) were entering as nest site in a dead tree stump (probably Silver Birch (Betula pendula) ) by one hole, near the ground, but instead of leaving by the same hole, exiting via another, higher up.
The two holes are marked on my photograph:
The adult was (or were, if both parents were involved) obviously bringing in food to feed nestlings inside the tree trunk. We observed five visits to the nest, and on four occasions the adult left by the higher hole. On the other visit, it left by the hole used as an entrance. At no time did we see more than one adult at once. Did each member of the pair perhaps favour one exit over the other?
I managed to grab a brief video of the final visit, using my HTC Desire HD, which I subsequently cropped heavily using Avidemux video editing software. The entrance is used in the first second or two, so you’ll have to pay close attention! Then there’s not much to see until it leaves 12 seconds later.
Unfortunately, pressure of time prevented further study.
Presumably, the nest was below the bottom hole — so why did the bird(s) pass that hole to leave by the higher one?