A capon, a gallinaceous bird that has been rendered sterile, typically less than a decennary old and with a mass ranging between six and nine pounds. It possesses a greater proportion of flesh and is endowed with a higher degree of succulence when compared to the average fowl.
This passage is describing a term used for a male chicken that has been castrated and raised specifically for use as a source of meat. These chickens are typically killed when they are between 6 to 9 months old. The term used to refer to these chickens is “capons.”