A wildlife photographer has captured a picture of a black skimmer bird feeding its chick a cigarette filter on a beach in Florida, USA.
In a Facebook post, Karen Mason said she had happened upon the pair on St Pete beach outside Tampa last month.
She urged: "If you smoke, please don't leave your butts behind."
The UK's RSPB, which described the picture as "heartbreaking", says nature is struggling to adapt to human littering.
Ms Mason also captured another picture of the chick carrying the filter in its beak:
Birds can mistake the filters for food and feed them to their young.
"Many birds are curious about the things we casually discard, and will often investigate to try and find out if something is food or not," a spokesman for the Royal Society for the Protection of Birds (RSPB) told the BBC.
"Sadly, this parent has decided the cigarette butt is something to feed its chick.
"Nature is struggling to adapt to the things we are doing to our planet; every year, we see more animals trapped, injured or killed by man-made products. We are even seeing litter being used as nesting material.
"Unfortunately for many people, littering seems harmless, at worst it makes an area look untidy; however, heartbreaking images like reveal the true impact of littering on our wildlife."
Cigarette filters are usually made of plastic fibres (cellulose acetate), and take years to break down in the environment.
They are the most common item of rubbish collected from beaches globally, according to conservationists.