I'd say it is the former. There is absolutely no reason why there shouldn't be a any birds there.So is it a case of the human brain not registering the birds there or the actual absence of them?
I know someone who was stationed near Belsen in the sixties - he says there were no animals, no birds there at all. He also said that no birds flew over and animals would take a detour round the site than cross it. How true this is or whether he was telling a ghost story I don't know, however this guy isn't one given to hyperbole.
I bet everyone who goes to Auschwitz is chilled by it and I can't see why animals wouldn't be able to pick up on human fear (from scent, body language, movement patterns etc) and react accordingly?
It's hard to put into words the 'feeling' of a place like Auschwitz but moose could have a point about 'mental' blockage, even if you're normally aware as a birder of birdlife around you when you visit various places. On entering the Camp, the first thing visitors do is enter the 'museum/lecture' room and watch a horrific realtime b&w documentary of what went on there. Up to entering, I'd been scanning skies/horizons for raptors etc and was pretty keyed up, but then it's like a complete paradigm shift in perception - birds become the last thing you are aware of other than the very strong realisation that none are singing as you start to walk to the 'huts' and the confirmation that the old adage is true. The gas chambers are also the first building visible from the car park. Bizarrely, there's no reason why there shouldn't be a good population of birds there, the Camp itself has many surrounding trees and the gas chambers are set against a backdrop of healthy woodland. The great wrought iron writing carved into the overhead entrance arch: 'Arbeit macht Frei' (sp?) stops you in your tracks though and the idea of birdwatching not only dissipates completely but belongs to another era - from then on, it's piles of shoes and false teeth and weeping Jewish pilgrims that dominates the conscience. Perhaps a return visit, with the primary objective of focussing on birds and an effort to deliberately 'de-sensitise' yourself with your surroundings may prove birds dwell 'happily' there, abeit silently!
I know it sounds pretty obvious, but aren´t birds pretty silent everywhere for much of the year? I mean, if you visit the woodland near my house in Spring, you can´t hear yourself think for the birdsong. But if you visit in November, it´s deathly quiet. I´m not trying to support or dispel a belief, just stating the obvious, with apologies.I was about five or six time in Auschwitz in the past time, in different seasons. And I remember that I saw different tits, chaffinches, different sp. of corvides and buntings.