## 1 Introduction  
Nowadays, there is an increasing need to study the behavior of laying hens, including their nesting behavior. This is partly justified by the fact that in the poultry industry, animal welfare aspects come to the fore with regard to the conditions of the laying hens [1], a central element of which the technology is the 'nest use'. The examination of the nesting tendency is also extremely important from an economic point of view, as the egg is the product that is sold commercially and from which the producers achieve sales revenue. Because the discussion concerns a basic food, the most important aspect is first the health and safe care of consumers; these health aspects are mostly influenced by where and under what exact conditions the eggs that reach our tables come from, i.e., 'which nest it comes from'. In the European Union, a significant change related to the welfare of laying hens was formulated more than two decades ago resulted in the use of traditional cages being banned on 1 January 2012 [2]. In these prohibited, old, traditional cages, there were no nests, which could cause frustration and stress for the hens which, according to some researchers, caused the hens to develop harmful and bad habits [3]. Moreover, it also manifested itself in the retention of egg-laying [4]. Among the many provisions of the European Union directive, there was one provision that wished to support the natural behavior of laying hens by making the use of nests mandatory in various housing systems, even in the case of furnished/modified EU-compliant cages. After these developments, there is no question that the nesting behavior should be given special importance among research of the hen's natural behavioral repertoire. The changes that affect the housing systems of laying hens may not yet be finished, as in the beginning of the 2020s, the voice of the consumer group in Europe (see the 'End the Cage Age' movement) that has demanded a ban on cage systems that are still licensed has become increasingly louder. In these alternative housing systems, the houses are group-mounted but individual nests are created, which primarily satisfy the seclusion and protection needs of the hens [5]. If these systems are ended, non-caged, i.e., other alternative housing technologies that provide more space and freedom of movement for hens will soon prevail, which will present a new challenge to egg production professionals and farmers. As someone must pay for the 'freedom' of the hen [6], increased production costs will cause price increases at every stage of the egg's journey (from producer to table), and as a result, eggs will become more expensive. In Europe, due to the decrease in the proportion of cage housing, the 'litter egg' has appeared in alternative-non-cage-keeping technologies that also include littered scratching areas, which is completely unknown to cage keeping. Unfortunately, it must be accepted that in alternative husbandry technologies, to a greater or lesser extent, there are always litter eggs, which, depending on the contamination of the shell, are not easy to sell, not to mention the potential human health risks. All of this significantly worsens the efficiency of egg production and income generation, as well as the production of eggs that are safe for consumers. In alternative systems, in addition to a larger group size, the laying hens have more living space, have a richer behavioral repertoire, and have a much more direct contact between individuals in the group, which is why it is of particular importance to understand the behavior of laying hens with greater depth under the changed housing conditions. To promote the development of husbandry technology systems and improvement of production efficiency, it would be useful to know why laying hens choose a specific point of the littered scratching area or the nest for oviposition (laying eggs), as well as what preferences prevail when using multi-level egg nests. Thanks to the ethology of farm animals, we already know much about the behavior of hens.