[Anke]

Interesting to read about all these dead cockerels... and all of them traditional pure breeds... one thought just occurred to me: All these breeds were developed BEFORE the advent of properly mixed poultry feed, often given now ad lib.... maybe these cockerels are just a wee bit too large for their (traditional) heart size? In older times nobody used to actually feed the hens, they got leftovers (if the dogs didn't get there first) and a handful of corn in the evenings... they had to scratch and run around the farmyard for their grub... so maybe one explanation  is that we all (including myself, though no dead cockerel here recently) keep our hens too well nowadays?

[northfifeduckling]

Do you have any larger male fowl - geese or large breed ducks for example?
Amorous males will try to mate chickens and because of their size, they squash and suffocate smaller fowl.

my drakes would never go for a chicken! Although they are quite a bit smaller - the respect is huge 

Regarding the sudden deaths - could they still have  been a bit anemic from last year's mite infestation? I take it most of us had the problem at some point? I heard that this can happen.
shame you didn't get your sunday roast yesterday, Laura! Maybe he knew about your plans and died of fear !