If you’re like me, you look forward to crawling between cozy sheets for some shut eye. For much of my life I’d been a decent sleeper and able to power nap, waking up feeling refreshed. I worked the afternoon shift – 3pm-11pm – for ten years and then, two decades ago, switched to getting up at 6am for my commute via ferry. As I age I have lost the ability to drop off easily and sleep through the night. That’s a concern, not just because I often wake up tired, but because sleep is integral for our physical health. We know that sleep disturbances in people are associated with diabetes, heart disease, dementia, weight gain and immune system issues.
In observing my birds I can see they sleep in different ways: standing on the roost bars, sometimes with their necks lowered; in a ball, with head under wing; or sprawled on their side. I see folks who hold their chickens that seem content to fall asleep on their back – that’s a real sign of trust, as they are totally vulnerable to potential danger.
REM (rapid eye movement) sleep occurs in mammals and birds. For us, it can last for a few minutes to an hour, while just a few seconds in birds. This is the state in which we – and every other REM sleeper – dreams. I know when my dog is experiencing REM sleep because she starts to whimper, her eye lids flicker and legs move wildly. I imagine she’s thinking of swimming or running. Apparently chickens dream as well, probably about food and dust bathing. We might think the brain has shut down, but it’s working just as hard when we are awake as when we’re sleeping.
All your experiences of the day are consolidated into memory during deep sleep (slow wave sleep). This type is dream free and allows the brain to rest. When I don’t get enough of it I sleep longer and more intensely the following night. The same is true for chickens, who are able to catch up by sleeping more deeply later on. SW sleep can last for hours in people, while chickens take short power naps. As prey animals they can’t afford to be out of commission for lengthy periods of time.
Folks might refer to chickens as ‘bird brains’, but they have relatively large brains in order to learn language, map their territory and recognize the members of their flock.
One of the cool differences between us and chickens is they have an additional type of sleep: uni-hemispheric slow-wave sleep (USWS). A chicken’s brain is divided into two hemispheres: each eye is connected to the opposite hemisphere, so they can actually sleep with one eye open and the other closed. This allows them to be both awake and asleep at the same time: the brain recharges while also remaining alert for predators. When they are sleeping in a more risky situation, they will increase the proportion of their sleep with one eye open and half their brain awake.
Do you have a coop cam? I haven’t set mine up yet, but when I’ve watched night time footage from other folks’ coops I’m always interested in how much they move around and jockey for position. You can tell a lot about the hierarchy of your flock based on who sleeps where. If you have staggered roost bars, birds with the highest status will be on the top rung. If your roosts are all on the same level those who are lower on the pecking order are on the periphery.
When birds sleep in a row the ones who are most protected (i.e. in the middle) can sleep with both eyes shut, while those on the edges are more alert for potential danger and need to sleep with one eye open. At some point during the night they swap positions: there are sentries on rotating watch duty, so by morning everyone gets a good sleep. This strategy ensures the overall health and safety of the flock is maintained.
So when does sleep start? A study from McGill University found that unhatched chicks go through sleep cycles. Although they are actively growing and moving the chick’s fetal brain would consume too much oxygen if it was awake for long periods of time. Their brains slow as a way to conserve the resources they have available.
The researchers found that the chicks’ brains were fairly inactive until @day 17 of their development inside the egg. The embryos didn’t respond to loud sounds but, interestingly, they could recognize the sound of a hen making a danger call.
Chicks, like human babies, require a lot of sleep. Those raised in brooders, without the influence of a hen, tend to have unsynchronized resting patterns and may be sleep deprived due to constant disruption from other chicks.
Less time being exposed to light – either natural or artificial – has been connected to better sleep, decreased mortality and better feed conversion.
So now you know a little more about sleep what does this mean?
- Chicks need sleep, and lots of it. They do best raised by a hen with hatch mates of the same age. If placed in a brooder it is better that they are with chicks of the same size as disruptions in their sleep can affect health outcomes.
- Sleep disturbances contribute to stress and lowered immune system function.
- For those that consider using supplemental lighting throughout the winter to improve egg production I would advise against it for two reasons: forcing hens to lay more than they would without lighting often predisposes them to reproductive tract issues and, as discussed, chickens need uninterrupted sleep. Being under lights does affect the quality of their sleep.
- Think about the placement of your roost bars and how that can promote healthy flock dynamics. Mine are all on one level with plenty of space so there isn’t competition.
- Chickens’ natural instinct is to roost as high as they can to avoid predators. If they are sleeping in the nest boxes it might be because the nest boxes are too low or there is an issue in the pecking order.
Credits: Acta Agriculturae Scandinavica; New Scientist; Your Chickens. Featured Photo: Edwin Yang