What is smothering?

Smothering happens when birds mass together, often on top of each other, resulting in death from suffocation. It's one of the biggest causes of death in freely housed commercial birds.

"Smothering is particularly problematic because it's difficult to predict and even more difficult to control," says poultry researcher Dr Ashleigh Bright. She studied smothering and possible causes on free-range commercial farms in the UK and found three general categories.

Panic smothering: can occur at any time, usually a one-off event caused by a predator, vermin, sudden noises, or changes in light, typically involved 20 birds or so.

Nest box smothering: most common when hens start laying and one hen visits/ uses a nest box, stimulating other hens to crowd into the same nest box.

Creeping smothering: the most common type of event with an unknown cause. Possible triggers include timing (for example, when the temperature drops and birds naturally huddle to stay warm). Usually involves 1-10 birds, can occur at any life stage.