This is what's written in Arthur Spiderwick's Field Guide to the Fantastical World Around You about Cockatrices.
Cockatrices (Family: Serpentigentidae)EditThe cockatrice can cause death with a single glaze. Reports indicate anything catching sight of the lethal bird's eyes is turned instantly to stone; but just as deadly is their poisonous saliva, able to fell even an elephant!!
Also known as a basilisk, the cockatrice has the head and feet of a cockerel and the tail of a serpent. The cockatrice is believed to be to product of a seven-year-old cockerel's egg, laid during the full moon and then heated for nine years by a serpent or toad.
There are few ways to protect ones' self from a cockatrice. One is to carry something reflective — like a mirror — and turn the creature's gaze back on it. Another is to keep either a weasel or cockerel nearby. The weasel is said to be the mortal enemy of the cockatrice, but the crowing of the cockerel is even more effective, causing the cockatrice to have fatal fits and to thrash itself to death.
- European Cockatrice (Basilicus europeanus)
- False Cockatrice (Scientific Name Unknown)
Even in the Invisible World, mimicry exists. Note the lack of horny specimen on the heads of these fantastical cockerels. This is the key feature in differentiating between these and true cockatrices. Their feathers mimic the dangerous creature, so predators leave them alone.
Arthur pictured the Cockatrice in warning stance with the colorful neck frill fully extended and the feathers ruffled.
Arthur Spiderwick at some point found a dead specimen on a farm, together with a petrified mouse. When he showed the mouse to the farmer, the latter revealed a cigar box filled with stone mice.
The Basilisk was said to be the King of Serpents, and looked like a giant snake with a crown on its head or the head of a cockerel. It had the same abilities as the Cockatrice. In modern fantasy, the Cockatrice and Basilisk are often mistaken for the same creature.