I agree with it being possible Infectious Coryza, but Infectious Coryza doesn't normally cause gurgling. I have a feeling you're dealing with 2 diseases at once. ILT is known for gurgling within the trachea.
In my experience and research, this unfortunately looks like the extremely serious Infectious Laryngotracheitis Virus (ILT). ILT is a viral herpes infection of poultry, but more specifically chickens most commonly primarily, but in severe strains, can affect other poultry fowl. The most common way for birds to contract ILT is by bird to bird contact (a carrier or another symptomatic bird). It is assumed that this disease can be given from infected parents to the offspring, as this dangerous virus can be transmitted vertically into the eggs of developing embryos, making any chicks that hatch, always infected and sick with the virus. So please don’t ever breed from your sickly infected flock to sell or giveaway chicks/hens/roosters to anyone. You can freely choose to hatch for yourself, but you should not ever sell and or giveaway any extra roosters as you’ll just be giving someone else your flock’s disease, causing them a devastation. ILT is a permanent lifelong chronic disease- meaning, that you can treat or have the symptoms go away, but whenever the bird gets stressed again, the symptoms will keep coming back or get worse. All birds (even recovered birds) remain lifetime long carriers of this serious viral disease, spreading and shedding it through their feces, feathers, dander, respiratory secretions and other bodily fluids. ILT is a distant cousin of the Mareks Disease, which is also caused by a Herpesvirus, more specifically, Gallid Herpesvirus 2. ILT is caused by Gallid Herpesvirus 1, so by keeping this in mind, it’s not only an extremely low risk of Mareks Disease, but also something that could wipe out a whole flock easily. This is a serious permanent lifetime disease of chickens and is incurable and untreatable. Since ILT is caused by a virus, antibiotics cannot help with symptoms. ILT has to run it’s course, but since this disease slowly suffocates the bird because of the large amount of bloody thick mucus buildup in the trachea and lungs. If your bird is making congested, gurgling sounds, coughing with or without bloody mucus, it is VERY critical to get your birds tested by a necropsy to find out if you’re dealing with this disease as soon as possible! Especially since ILT has a high mortality rate, especially in chicks and younger birds. That being said, it is recommended to cull all birds, disinfect and start over fresh. If you’d rather not (though I firmly believe it’s horrible to keep birds infected with ILT alive as it’s selfish), then the other option is to keep a closed flock- no new birds into your flock and no birds leave your sick flock. If you choose to start over, always quarantine any new birds that you decide to bring into your flock, 30 day quarantine isn’t always enough, therefore, it’s best to do a 60 day quarantine AWAY from your healthy birds, in another area. I did not write this out to scare you, I wrote it to offer information, help and advice about how serious this specific respiratory disease is, because people don’t take ILT seriously as much as they should.
More information about ILT:
https://extension.umd.edu/sites/ext...programs/poultry/ILT Know the Symptoms....pdf
https://www.agriculture.pa.gov/Anim...tious Laryngotracheitis Virus (ILT) Facts.pdf
https://www.oie.int/doc/ged/D9312.PDF
https://www.michigan.gov/documents/mdard/ILT_Basics_sup_mang-Web_645631_7.pdf
http://www.omafra.gov.on.ca/english/livestock/poultry/facts/ilt.htm
https://www.tahc.texas.gov/news/brochures/TAHCBrochure_ILT.pdf
https://ucanr.edu/sites/poultry/files/246952.pdf
https://content.govdelivery.com/accounts/MNBAH/bulletins/1cf3b20
https://tvmdl.tamu.edu/2018/02/01/infectious-laryngotracheitis-diagnosed-laying-chicken/
https://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex2216/$file/agdex_663-36.pdf
https://www.business.qld.gov.au/ind...seases-disorders/infectious-laryngotracheitis
List of testing and necropsy labs for poultry & other animals:
• List of US Poultry Labs -
https://www.heritageacresmarket.com/poultry-necropsy-labs/
• List of Poultry Authorized Labs (NIPIP) -
https://www.poultryimprovement.org/documents/AuthorizedLaboratories.pdf
• Zoologix PCR testing for livestock (poultry, equine, bovine, avian, etc) -
http://www.zoologix.com/avian/index.htm
• USDA Diagnostic Tests -
https://www.aphis.usda.gov/aphis/ou..._Lab_Information_Services/SA_Diagnostic_Tests
• Research Associates Lab (RAL) -
http://www.vetdna.com/test-type/avian-bird
• Poultry Health Services Diagnostic Tests -
https://www.poultryhealthservices.com/lab/tests/
Since I am NOT a veterinarian, I can NOT officially diagnose your birds- but I CAN give you this SUGGESTION as this is what it COULD BE. I also can NOT offer antibiotics or medications until you get testing done to know what it is exactly your flock has. Do NOT go to ANY avian veterinarians as they know NOTHING about poultry diseases and health- it is also a waste of your money! Get testing done from one of the links above!