Layer pullets prioritize roosting location over perch diameter at night

Perching and roosting are highly motivated innate behaviours of laying hens that evolved as anti-predator responses in their wild jungle fowl ancestors, providing elevated, usually protective vantage points for the birds. Although current management guidelines require that perches be provided to pullets in non-cage systems within the first week of age, there are few recommendations and little research on specific perch characteristics (e.g., shape, size) for young birds compared to adult laying hens. This study aimed to assess the relative daytime perching and nighttime roosting preferences of growing pullets for round perches of varying diameters and spatial locations. Dekalb White (n = 75) and Bovans Brown (n = 75) layer chicks were housed in groups of 12 or 13 in 6 floor pens/strain (N = 12). Each pen had 3 round wooden perches of differing diameters: 1.91 cm (S), 2.54 cm (M), and 3.18 cm (L), all elevated 10.16 cm above the ground until 4 WOA, then moved to their final height of 82 cm above the ground. Perch locations were rotated weekly among three pen walls (A: wall closest to the room entrance, B: wall opposite pen door, C: wall furthest from the room entrance) to account for location bias. Video recordings of 48 h per week over four 3-week long periods from 2 to 13 WOA were scanned once per 15 min during lights on and once per hour during lights off to determine the percentages of birds on each perch (S, M, L), and at each location (A, B, C). Overall, elevated structure use increased with age during both the day and night (Daytime: P < 0.01, Nighttime: P < 0.01). While brown pullets used all perch diameters and locations similarly during the day, white pullets showed a consistent increase in use of M and L, but not S (P < 0.05), and of locations A and C, but not B, over time (P < 0.01). At night, no preference for perch diameter was observed (P = 0.20) but more pullets consistently preferred to roost at location B, facing the interior of the pen, compared with locations A or C (P < 0.01), regardless of age. These results suggest that while daytime perching in growing pullets is influenced by an interaction between perch diameter, strain and development, nighttime roosting is primarily driven by spatial location, likely reflecting vulnerability during sleep and the importance of elevated points for vigilance. Together this highlights the need to consider perch characteristics and spatial placement when designing housing systems for growing pullets.