Aggressive Behaviour & Cannibalism In Chickens

When we conjure up iconic images of chickens what comes to mind are often those associated with the maternal dedication a hen shows towards her chicks or soft clucky sounds of a barnyard flock or fluffy feathered butts. We don’t often think, and are even less often prepared, for the dark side of chicken behaviours.

Chickens use their beaks to explore their world, locate food and water, preen, and maintain their social hierarchy. Pecking is a normal behaviour, but when it is frustrated or curtailed by human management that activity may become problematic. 

Aggressive behaviour can be seen on a continuum from light feather picking to pecking injuries to full-on murder and cannibalism. Understanding the nature of those behaviours can help us put preventive measures in place without having to deal with an emergency on our hands.

Cannibalistic behavior includes pecking, tearing and eating of skin, tissues or organs of flock mates. It differs from simple dominance because it involves physical harm, but often starts out as simple feather pecking that is usually directed toward the body, toes, tail and especially the vent area.

I have crested birds and their heads are sometimes the targets for feather pecking at nighttime on the roost bars. It’s an annoying habit because as the new feathers are just emerging someone pecks them out again. There are products, like Stop Pick and Pine Tar, that you can put on an area to deter further picking. (Do not use BluKote, which is banned for use in chickens.)

I’ve only twice had to deal with pecking causing harm: once when I got new birds and a teenaged pullet caused a head injury to a smaller chick and the other time when a young hen had a prolapsed vent and the flock, attracted by the red colour of her reproductive tract, pecked at it causing further injury.

Vent pecking from flock members usually occurs immediately after a hen has laid an egg when the cloaca (vent) often remains partly everted exposing the mucosa, which could be red or bleeding. This form of pecking is somewhat different, in that, birds are attracted to the colour red rather than are motivated by aggression. The end result though can still mean pain, injury and, potentially, death for the victim.

My one brush with true cannibalism was several years ago. I had some teenaged birds housed in my grow-out pen, which was mostly, but not completely, netted from aerial predators. A hawk managed to get in and kill one of the 10 week old pullets. When my partner found the body her siblings were gathered round eating what the hawk had left behind. It’s was an unappetizing sight, but at least they weren’t responsible for her death.

The sad truth is it’s not uncommon that chickens can turn against a flock mate and cause life threatening injuries. Cannibalism is a learned behavior and, once established, can spread throughout a flock.

Causes Of Cannibalism

• Boredom: Chickens are active foragers and often on the move. If they are confined to a small space with little to engage them they direct their energy towards other, less healthy, behaviours.
• Changes In Routine: I can relate to chickens’ love of routine as I consider myself a creature of habit. Anything that changes their daily schedule can be a stressor and affect the whole flock.
• Competition For Food and Water: Chickens require access to both food and water throughout their waking hours. If there is competition for resources it is often the lowest members in the hierarchy that don’t get access to them. This in turn can contribute to weight loss and weakened birds and make those birds vulnerable to aggression from the flock.
• Dietary Imbalances: Inadequate amounts of dietary protein, salt or methione can lead to feather picking. Ensure your flock is on a balanced feed that is appropriate to their age and sex.
• Flock Diversity: I often see online posts from folks observing that their birds are ‘racist’, meaning ‘birds of a feather flock together’ based on breed or colour. Although it hasn’t been my experience there is some evidence that combining birds of different breeds, colors, or sizes that haven’t grown up together often upsets the social order of a flock and increases the chances of cannibalism. Mixing breeds with different traits can promote pecking (e.g. feathered legs, crests, or beards) due to curiosity about their flock mates feathers.
• Flock size: The social order of poultry in small flocks depends on individual recognition. In flocks with over 40 members there is less recognition of members leading to a less rigid hierarchy where birds become less aggressive and more tolerant of others. Small flocks promote a distinct pecking order that is more stable. Research indicates that flocks do best when either small or large rather than an intermediate size – the tipping point being around 30 birds.
• Heat: I live in the Pacific Northwest and don’t appreciate the heat of our Mediterranean-type summer weather – neither do my birds. Temperatures within the coop and ambient temperatures outside during the summer can lead to heat stress and dehydration and increased irritation between birds.
• Lighting: Birds forced to live under artificial bright lights don’t get adequate sleep, which contributes to stress.
• Reordering Of The Pecking Order: There’s nothing like having new, uninvited roommates to upset the apple cart. Every chicken flock has a very clear hierarchy, which requires shaking up and being reestablished with the introduction of new members.
• Overcrowding: Although chickens are flock animals and are often seen snuggling together on the roost bars, sharing nest boxes or rolling around in the communal dust bath they also require space. It may seem like they don’t use all the space that is provided, but you usually can’t have a coop or run that is too big. The recommended minimum floor space or roost bar measurements are just that – the minimum – and even at that they aren’t adequate for a stress-free flock. The prefab coops sold by feed stores touting that they can hold a particular number of birds are definitely too small. 
• Parasites: External parasites (e.g. mites and lice) can cause itching, self-pecking, feather loss and broken skin, which are attractants for pecking by other flock members.
• Sick Birds: Often sick and weak birds are the target of bullying and pecking. I imagine as prey animals this is an adaptation to rid a flock of a liability that might attract predators.
• Stress: There are a wide range of factors that contribute to stress in birds: transport; dehydration; fear; scares or attacks by predators; competition between roosters; over mating of hens; competition for nest box or roost bar space; poor ventilation; unsanitary conditions (ammonia build up, muddy runs); hormonal changes (i.e. puberty); exposure to toxins or pathogens; over handling; or being chased.

Prevention Strategies

• Provide adequate coop, run, nest box and roost bar space.
• Ensure that all flock members have easy access to food and water (set up multiple stations if there is competition).
• Manage interactions with predators to avoid stress, injury and loss of birds.
• Remove sick or injured birds and don’t return to the flock until totally healed.
• Use Stop Pick or Pine Tar on areas of feather picking.
• Allow hens to have seasonal breaks from laying without artificial lights.
• Deal with weather extremes that might cause stress.
• Carefully integrate new members to the flock.
• Separate bullies for a period of time (i.e. several days) to reset the pecking order.
• Treat both internal and external parasites in your flock.
• Add enrichments to the birds’ environment, especially forage-related activities.
• Attach Pinless Peepers (plastic blinders) to the beaks of aggressive birds.
• Eliminate access to dead chickens.

Commercial farms and feed stores routinely trim chicken beaks. I have never had a debeaked chicken – a procedure achieved by cauterizing chicks’ beaks to prevent potentially problematic pecking behaviours – and I’m not a proponent of this practice. Bird beaks are full of nerves and, like our hands, are very sensitive to touch, temperature and pressure. Chickens require their beaks and trimming them is not only painful, but deprives them of important sensory information. (Beak trimming is banned in Austria, Denmark, Finland, The Netherlands, Norway, Sweden and the U.K.)

The longer I keep chickens the more I realize that managing stress is the key to maintaining a healthy flock. I can’t overestimate the importance the role that stress plays in unwanted behaviours and illness in a small flock. In this case, identifying potential stressors and how to manage them will go a long way toward preventing feather picking, bullying, pecking injuries and cannibalism.

Credits: Dalton Engineering; Merck Veterinary Manual; Poultry Hub; The Poultry Site; Wikipedia. Featured Photo: Homesteading Basics.