Our smoke/CO detectors are electric but they also have a battery as back-up and, when the battery is going low, it starts to beep. At the beginning, the pauses between the beeps are long but, if you don't change them, they start speeding up until it's constant. The one in the parrot room had been beeping and I had been telling my husband about it but he did not change the batteries until it got real bad and, the next day, there was the BEEEP BEEEP again! I accused him of not changing it - "No, I DID change it!" - then I accused him of putting an old battery in it - "No, they were brand new!" - Well, he went crazy looking everywhere and changing all the batteries in all the detectors - but the BEEEP BEEEP BEEEP kept on... Until I realized it was the parrots doing it! Thankfully, whoever it was that had learned it apparently lost interest in doing it because it has stopped.