Re: Eh, Bird Vortex?
The proximity of the high wall (shelter)? Texture/material of the roof (it looks different - better traction, darker colour = more warmth?) Closeness of 2 walls (more safety? less wind? Body heat containment?) Absorption of sunlight on the higher chimney (more warmth emitted)?
I learned lately that pigeons breed year 'round, even lay eggs and nest in the northern winters----brrrrrrrr!! --- they're not the spring songbird type.
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