## 2 Materials and Methods  
The research was carried out at the Poultry Testing Station of the Kaposvar Campus of the Hungarian University of Agriculture and Life Sciences, with a flock of laying hens of three different genotypes provided by Babolna TETRA Ltd. (Figure 1). They were:  
* Commercial brown layer hybrid (C);
* Purebred paternal offspring group (Paternal);
* Purebred maternal offspring group (Maternal). The set numbers were: N = 318; \(n\) = 106 hens/genotype; 53 hens/pen, i.e., these were the conditions per group. It is important to emphasize that the laying hens were not beak-trimmed. The temperature in the barn was usually 14-18 \({}^{\circ}\)C, where we used 16 h (5:00-21:00) of lighting per day with a light intensity of 30 lux. The laying hens could consume commercially available egg feed and drinking water ad libitum from the suspended feeders and drank water from a suspended open water drinker. Figure 1: The experimental flocks with the three different genetic backgrounds (commercial hybrid (**above**) and the purebred offspring of the paternal (in the **middle**) and maternal lines (**below**)). We placed 53 19-week-old pullets in each of the six indoor alternative pens, each with a floor area of 5.52 m\({}^{2}\) (1041 cm\({}^{2}\)/hen). One-third of the floor space of the pens were littered with soft wood shavings; the remaining two-thirds of the area were a raised level, plastic grid platform. In the littered part of the scratching area, the thickness of the soft wood shavings was 10 cm, while the raised plastic grid platform was set at a height of 23.5 cm apart from the level of the littered scratching area (Figure 2). Figure 3 clearly depicts that 14 nests with artificial grass were provided for the hens on two levels per pen (3.8 hens/egg nest), whose design and dimensions (W: 24.5 cm; H: 18.5 cm; D: 33 cm) can be seen in the Figure 4. At the entrance of each nest, there was a 10 cm high plate cover (=threshold). The entrance to the bottom and upper egg nests were 24 cm and 65 cm above the level of the plastic grid platform, respectively. Figure 3: The image taken by an HD camera shows the position of the nests located on two levels in one of the pens installed for the Maternal Line; an infrared camera was installed above the nests. Figure 2: The floor plan of the alternative pen and the layout of the technological devices. In front of the row of nests, 2-2 pop-up slats per level (Figure 3) assisted the approach to the nests. The laying hens were able to enter the nests from the plastic grid platform. The height placement of the nests and pop-up slats made it easier for the laying hens and did not hinder them from entering the nests. During the whole test period (12 production months), the eggs were collected at exactly 10 o'clock every day. We separately recorded the number of eggs laid in the nests on the lower and upper levels, as well as the number of eggs laid in the scratching area in the litter. Infrared cameras (GeoVision Target H.265 4.0 Megapixel outdoor IP Eyeball dome camera) were installed above the row of nests in the alternative pens (Figure 3), and we captured 24 h recordings using a special software (GeoVision GV-NVR System). The video recordings were a continuous recording. When studying the nesting behavior of laying hens, the number of times the birds visit the nests in different positions is telling information (see: Figure 2). That is why we considered it important to be able to track the number of times the laying hens visited the 7 egg nests placed on each of the two levels, i.e., a total of 14 nests, even over the course of a test day. Because the 12-month egg production period is quite long, we took special care to choose the appropriate time for the examination. We decided to carry out the evaluation of the recordings at the beginning of the third production month, as based on the literature recommendations of Babolna TETRA Ltd., the tested genotypes reach their peak production intensity as a breeder around that time.