Reproduction - the hen
- The start of sexual behaviour is greatly affected by the environment, especially feeding, lighting regime and genetic strain.
- In the wild and in free-range systems, young females (pullets) show mating behaviour as early as 18 weeks of age, but this varies greatly.
- Most hens, regardless of breed, start to show mating behaviour 4-8 days before the start of the new laying season - whether there is a male present of not.
Egg laying and nesting
- The egg-laying behaviour of hens is very elaborate, and the selection of a nest is done with great care, often in association with the male.
- Studies have shown that nesting activity and ovulation are linked so a good nest favours high production.
- Nesting is characterised by secrecy and careful concealment, and nest selection has four phases.
- First - seeking a place to lay. This can be very protracted as the hen becomes restless, paces about giving the pre-laying call and showing characteristically body postures. In a deep litter-laying house, she examines the walls and corners.
- Second - inspection of a number of possible sites between feeding, preening or sleeping, and finally pushing into one of them. Inside she continues her examination, lifting her legs with care with her neck horizontal.
- Third - settling, squatting and making a nest hole by crouching and rotating several times using her keel bone to shape the nest. Then she sits and lays, often standing to expel the egg.
- Fourth - after laying she may continue to examine the egg with her beak then rises and returns to the flock cackling.
Nesting behaviour in cages
- In the limited space of a cage, the hen adopts the same behavioural sequences but obviously, their expression has to be modified.
- In a multiple-bird cage, which most commercial ones are, the hen about to lay searches the cage pushing other hens away. She may creep between the legs of other hens, sometimes 100 times before she settles.
- She spends laying time putting her head between the wires, pushing and often being pecked by birds in the next cage.
- Intentional movements to try to fly may be shown by tail extended and wings slightly raised. She may even try to climb the cage.
- Then suddenly she squats and lays. Her breathing rate is high and her calls are generally weak. Eggs are often laid in the same area of the cage before they roll away.
- Caged hens paces to fill up the time normally spent in the pre-laying behaviour seen in free-range birds. Pacing varies between strains from 100-2600 paces before laying.
- Birds have been recorded as spending 55% of their time resting, 21% eating, 17% laying and 7% drinking.
- In the wild Jungle fowl, nesting is mainly on the ground in a bamboo habitat with semi-darkness and shadow patterns.
- In domestic fowls, we want them to nest in boxes off the ground to keep eggs clean, but which still mimic their natural preferences.
- Generally, one nest is needed for every four birds. Nests should be clean and have ample litter such as straw (a favourite), shavings, sawdust, wood fibre, and so on. The key is to stop birds from sleeping in the nest boxes or using them as roosts.
- The box should be large enough for the bird to turn round.
- Studies have shown a bird preference for a triangle-shaped entrance, and some for a square one. Boxes are best sited 450-500 mm above the ground litter.
- Leaving dummy eggs in the nest is an old trick to encourage hens to lay, but the hen is probably more attracted to the nest litter than the eggs.
- Some systems use communal nests of 60 x 200 cm that can accommodate 50 birds.
- Hens have been identified as those that prefer solitary nests, and others that prefer communal nests. Communal nests have more behavioural problems caused by shy birds not wanting to use them, and birds crowding inside them and keeping others out.
- Breeders use trap nests where the bird triggers a slide with her tail and has to be let out manually after recording her Identification number with her egg.
Written by: Dr Clive Dalton