[Jolly2 (OP)]

Does anyone know why cockerels feel the need to crow every morning? Surely it attracts predators and it an evolutionary negative.

[evan_au]

Marking a territory, advertising his masculinity and dominance and issuing a challenge to any contenders.

[Bored chemist]

Demonstrating to any hens in the area that he's big enough and brave enough not to worry about predators.

[alancalverd]

Most male birds sing at dawn. It just happens that chickens invented Grime.

[charles1948]

As a follow-on, why are hens traditionally reputed to make a cackling noise after they've laid an egg?

It doesn't seem a sensible thing for a hen to do. As it advertises to predators, that there's a fresh egg available to capture and eat.

Do hens actually do it.  If so could it be a vocal signal directed.at the cockerel, calling for help to defend the egg

[alancalverd]

Do hens actually do it. 

Mine do. Then they walk away and get on with the serious business of destroying the garden whilst the egg freezes.

I don't think you can regard the domestic chicken as a normal bird. Every other species in my garden lays a clutch of eggs once or twice a year then either takes turns with the male to brood them or sits on them and gets fed by the male until they hatch. The idea of laying and abandoning one egg every day doesn't make sense.  Now and again one of the girls "goes broody" and sits on everyone's eggs for a few days but she pretty soon gets the message  that, in the absence of a cockerel, even that level of normal avian behavior is unproductive. And they can't claim they are being drugged - until the outbreak of avian flu, mine were entirely free range but had the wit to huddle together in a henhouse at night, and always lay in the nestbox. Weird and wonderful creatures.

[charles1948]

Thanks Alan. A very interesting and informative post.