Bird are no different to humans some are house proud where as some could not careless how dirty there nestbox gets. One of my hens will not leave the nestbox once she starts sitting the eggs unless l tap on the box for the daily inspection. It appears she is reluctant to use the outside toilet and insists on using the nestbox as the toilet, which causes problem with eggs becoming addled or infertile. Only the first egg is fertile so to overcome this l remove the first couple of eggs and only replace the eggs once the third egg had been laid. Normally l would replace the first two eggs with plastic until the third egg is laid but to encourage the hen to leave the nestbox l only put the eggs back after the third egg.
The nestbox was a mess and the bedding had to be changed the hens backside had the biggest solid faeces attached to the under down feathers. Scissor out and the soiled feathers were cut away and a quick clean up the hen was released to continue feeding the 1st chick of 2016. I did think l was going to lose the hen after she had endured such a ordeal but within two days she looked fine and continued to feed the chick.
The other boxes are completely different clean and not to much faeces in the boxes while the eggs are being incubated but as we all know this will change when the chicks start to hatch.and it is good practice to change the bedding on regular intervals to prevent diseases taking hold.
The nestbox bedding always has a small amount of diatomaceous earth added to prevent any lice or mite from taking hold.
Livestock breeding is not a exact science but l cannot stress to you spend as much time as possible with your birds and you will learn far more from studying your birds than reading articles. The birds have character and l can normally recognise a bird who is under the weather and if you act quickly you may be able to save the bird.