Well, I am coming to join my fellow members above and add one more location in which cloudy days are common and that as we edge toward winter, ever shorter days!
As started, Blight Sunshiny Days is an a fairly standard day for Amazons in their Natural Ranges! Yes, during the day, clouds move in, it rains and the clouds move out fairly quickly and even more true in the rainy season. But when compared to where the four of us live! The Natural Ranges have easily 50% more Sunshine!
Kiwi's mom suggested Featherbrite lamp to bring a bit of Sunlight into your Amazons day and I would agree that using any of the LED, Day Light Bulbs will keep both your Amazon and you happier! This type of bulb provide a color of light that is 'like' Full Spectrum Light provide by the Sun!
It is not a replace for the Sun's light, but can be used on those days when the Sun is covered by Clouds or has gone missing for several months during the Winter!
Warning: Do not provide this type of lighting for more than eight (8) hours during the normal daylight times! Either use a dimmer or change to soft light bulbs during non-daylight times. Full Spectrum Lighting when provided by light bulbs can disturb sleep schedules as the mind confuses day /night caused by over use.