It seems like they don't mind the rain. their feathers are water repellent
This is what google says:
How are birds' feathers waterproofed?
Birds are able to keep their plumage waxy and water-repellent even in the wettest conditions by preening tail to top. ... Birds pick up oil on their beaks, by rubbing against the uropygial or preen gland near the tail, and then rub it over their feathers. ... As water cannot penetrate.
This is what google says:
How are birds' feathers waterproofed?
Birds are able to keep their plumage waxy and water-repellent even in the wettest conditions by preening tail to top. ... Birds pick up oil on their beaks, by rubbing against the uropygial or preen gland near the tail, and then rub it over their feathers. ... As water cannot penetrate.