Gaping Hen

The gapeworm Syngamus trachea) buries its head in the lining of a bird's windpipe or other part of the respiratory system, causing "the gapes" or "gapes". Gapeworms get their name from the habit and infected bird has of continually yawning or gasping for air. these worms, which are big enough to be seen without magnification, are also called "red worms" or "forked worms" - each blood-red female has a somewhat paler male permanently attached forming the letter Y.
Gapeworms cause considerable losses in free-ranged flocks, particularly those associated with adult turkeys. This parasite is especially serious in young birds; older chickens become resistant.
An infected chicken coughs up worm eggs, swallows them, and expels them in droppings. The cycle is either direct or indirect, involving earthworms, snails, and slugs. Eggs take up to two weeks to embryonate and may survive in soil for as long as 4 1/2 years.
Symptoms of gapes are yawning, grunting, gasping, sneezing, coughing (sometimes coughing up a detached worm), choking, loss of energy, loss of appetite, weakness, emaciation, closed eyes, head shaking, frequent throwing of head forward with mouth open to gasp for air, and convulsive shaking of the head (to dislodge worms from the windpipe). Gapeworms multiply rapidly, eventually suffocating the bird.
Infected small flocks are treated with either thiabendazole or levamisole.

Hope this helps some and I wish your flock the best.