LOL! Yes tree frogs are incredibly loud! I had about 5-6 singing to each other yesterday evening in the back yard and I could hardly hear my family talking to me while out on the deck! They are really hard to find too. I have one that retires to a little ledge on the top of my shed every year.....same spot. He's so cute! I love going to sleep with my windows open so I can hear them, but sometimes, I just have to close the window 'cause they are sooooooo loud! They are pretty amazing little creatures. I think they are attracted to my backyard because I have several little water gardens. They deposit their eggs in the water. They are so sensitive to the presence of water, that if I go out to just water a few plants, they start singing! I don't know if they see the water, or just hear or smell it! Ain't nature grand? :)

Yep, colours work out. Today I had the male show up too. Both birds are walking very diligently through my flower bed in search of seeds. They make quite a different sound when startled.

There are half a dozen subspecies of American robin. The ones from Newfoundland are sometimes called "black-backed robins", and in addition to being much darker than the more common subspecies are somewhat larger. Birds from the rain forests of the pacific Northwest are also very dark. Probably what you saw was an adult male bird from one of those subspecies.

I'm going to take a shot at my own question after just now finding a similar post from 7 years ago... also in a propane tank, same kind of materials. Consensus was Carolina wrens -- which I love, and which have been around a great deal. Do others agree? Carolina wrens?