One of my two RIR's started squeaking a couple days ago when she attempts to squawk. Her clucks still sound normal, though, and she's had some improvement with her squawks. It's now more of a mix of squeak and regular, but I'm still concerned. She's breathing fine, has a ton of energy, a strong appetite, poops normally, crop is normal. No discharge from eyes or mouth. No gaping, except in the late afternoon, when it's hot. We've had a heat wave for the past few days, reaching 100° or more. It's extremely dry here. Zero humidity. And with all the fires we've had in Northern California, pretty much every day is a "Spare the Air" day. Could heat or poor air quality cause this? My flock is just my two girls, and this one is my favorite. She's the less vocal of the two. She's a daily layer and rarely makes a peep when she's in the nesting box, but she's still pretty chatty in the mornings and whenever she sees me. Being squeaky hasn't changed that. Here's a brief video of her: Everything I've read has other symptoms. Her squeaky voice is her only symptom.