Birds living in busy cities are making themselves ill because they are singing louder and louder to make themselves heard above all the noise.
The birds, including robins, are having to sing really loud so that they can be heard over the traffic and loud sounds of city life.
But this means they are straining their voices and damaging their ears.
Some birds are even singing at night when it's quieter, but this is dangerous as they attract predators.
Also, this could spell trouble for the future as if birds can't be heard singing, or aren't singing properly, then they can't attract a mate and have babies.