Sight
  • Chick embryos respond to light as early as 17 days after the start of incubation.
  • A hen cannot rotate its eye very much but they can see a field of 300°, with a binocular field of 26°.
  • Hens follow moving objects by moving their heads.
  • Their acuity (sharpness) is good and they have good distance vision.
  • Hens characteristically lift their heads before jumping, and tests have shown that they can discriminate between squares, triangles and red and black dots.
  • Studies showed newly hatched chicks preferred to peck at blue objects rather than green or orange ones, although orange was preferred before green but not before red.
  • Chicks were found to differentiate between red-dyed liquid and blood.  Blood was very aversive to them.
  • Chicks learn quickly to avoid coloured feed if it makes them ill, and prefer to peck at round rather than flat objects.
Smell
  • Not much is known about how important smell is to poultry.
  • Hens are not keen on food that smells of mould or is sour, so presumably smell is involved in this feed rejection.
  • It’s suggested that birds can definitely smell blood.
Hearing
  • Hens don’t have an ear lobe but they have a well-developed ear.
  • Calls produced by hens range from 250 cpm (the broody hen “cluck”) to about 3000 cpm (the distress call).
  • Studies confirmed hens can hear sounds as high as 8000 cpm.
  • Research found that hearing in hens covered a range from 60-11950Hz with highest sensitivity from 815-2000 Hz which is their normal hearing range.
Taste
  • Hens have about 340 taste buds mainly on the palate and floor of the oral cavity.
  • They are rather indifferent to sugars but can detect glucose to about 2.5% in solution.
  • They tolerate a range of acid and alkaline tastes, and are sensitive to and avoid salty feeds.
  • Taste determines whether a hen accepts or rejects a feed and similarly to water.
  • Hens can detect water temperature differences of 2.8°C.  They will reject water that rises 5.5°C above their body temperature although they will readily drink freezing water.
Touch
  • Stroking, rotating and turning hens upside down will immobilise them for various periods of time.
  • In this state, although fully alert to their sensory surroundings, they can be conditioned or gentled to humans or other frightening objects.
  • After return to normal they will show reduced fear to the conditioned object.
  • Touching the back of a hen will often cause it to respond by a sexual crouch, especially if it is low in social rank.
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