Possible Clues:

• Bird now possibly in danger from fox to act cowardly
• Get too scared
• During cut in coke supply, hard to bottle it
• Get scared off, swish with whip inspiring cowardice ultimately
• Pig: "Hen, put the hammer down." Hen: "Catch you on the flip-flop: __."
• Lose heart
• Turn and run for notice, when poultry is going free perhaps
• Unfashionable to follow stylish man and turn yellow
• Be too scared to do something
• Turn yellow bird away