In Australia, 47% of all egg sales are from free-range hens. Anecdotal industry reports indicate that smothering can account for up to 40% of mortality in Australian free-range laying hens. Smothering occurs when birds mass together, often on top of each other, resulting in death from suffocation, but not all piling results in smothering. The present preliminary observations, which are part of observational and epidemiological studies on hen smothering in Australian free-range farms, aimed to characterise the piling behaviour of a flock of 22,514 Hyline-Brown laying hens housed in a free-range aviary system over a randomly selected 9-h observation period