I'm sorry about your chicken. Is it possible for you to make a portable wood and chicken-wire structure you can move about the yard so the chickens can scratch freely, and *also* restrain the puppy inside another fence so that she can exercise freely?
Springer Spaniels are among the sporting breeds in the United States (AKC system of breed grouping); they're a gun dog in the UK system.
Spaniels are among the oldest recognizable groups of dogs, along with hounds, pointers, mastiffs, and what are euphemistically called "Northern"/spitz dogs. The number of kinds of spaniels, as well as their appearance in old paintings and descriptions in literature, attests to their antiquity. The "springer" in their name refers to their ability to "spring" hidden game, esp. birds but also rabbits, from the brush.
I have a basic dog breed ID book next to me at the moment. Just leafing through the "gun dog" group shows how long Spaniels have been recognized as hunters and different varieties been developed for different regions:
Clumber Spaniel--Origins, 1800s
Cocker Spaniel (English)--[same]
English Springer Spaniel--[same]
Welsh Springer Spaniel--Origins, 1500s
Sussex Spaniel--Origins, 1700s
German Spaniel--Origins, 1900s
Irish Water Spaniel--Origins, 1800s
Epagneul Francais--Origins, 1600s
Epagneul Picard--Origins, 1700s
Epagneul Pont-Audemer--Origins, 1600s
and this isn't all of them. I left out two from this particular book, which itself doesn't claim to be complete.
Please consult experienced local dog people (a veterinarian, a Spaniel club, a dog trainer, an experienced groomer, an experienced pet sitter) who can see your physical set-up for the best ways to protect both the chickens and the puppy, soon to be dog.
Trying to train a Welsh or English Springer Spaniel NOT to go for game when five hundred or more years of breeding and training have it primed to do just that is very unfair to both the dog and the chickens. This time, the puppy was unhurt but the chicken died; next time, what if the chicken scratches the puppy's nose/eyes in the struggle?
Best wishes; hope it all works out.