Video footage from back in 2010 shows a bird feeding goldfish by dropping food into waiting mouths in the water. The caption included with the video, which was posted on YouTube, claimed that the bird would come back to the pond up to six times a day, dropping seeds into the mouths of the waiting fish.
This isn't the first, nor the last, case of animals catering to another species. Just recently, it was discovered that a lioness had begun to care for an orphaned leopard cub. Before that, news broke that a family of bald eagles had also adopted a red-tailed hawk chick. It's important to note that the lions and eagles adopted a member of an enemy species. There have been numerous accounts of animals caring for and nurturing members of other species, which have fascinated scientists and everyday people alike.
What, therefore, drives these animals to care for those not their own?
Carp, to which goldfish belong, have mouths that may remnd cardinals of the mouths of their young.
It seems that in these three cases, a primal instinct fuels the animals to commit what we would consider to be an act of kindness. It's the primal instinct to feed their young, and it triggers something in the animals that makes them act in an unusual way towards a member of another species.
The lioness who nursed the orphan leopard cub had cubs of her own, and was likely overtaken by her maternal instincts. The bald eagles, meanwhile, also had chicks still in the nest. Christina Riehl, a biologist at Princeton, guesses that the goldfish's open mouths reminded the cardinal of the open mouths of hungry baby birds. The cardinal then reacted the way nature intended for it to react.
It does make sense that the goldfish would remind the bird of its own young. Baby birds still in the nest have mouths in vibrant colors, likely in much the same way that goldfish do. The baby birds' mouths are often red or yellow, serving as a visual cue for parents: food goes here. It's a testament to how small, simple stimuli can trigger very deeply ingrained behavior in animals.
That, therefore, is why there's nothing really all that weird or strange about this bird feeding goldfish.
Baby cardinal mouths do look a little like carp mouths.
There may be nothing weird about it, but it certainly doesn't help the bird, at least in biological terms. If it has young, it means that it's feeding the fish instead of its own offspring. However, it's also possible that the bird had lost its young recently.
Of course, this is advantageous to the fish, who can easily learn to go where they know there would be food. Thus, it's safe to assume that every time the bird passes by, it drops food into the waiting mouths.
Surprisingly, other types of birds have also been found to feed fish as well. There is also footage of black swans and ducklings feeding goldfish. However, Riehl says that not every bird feeding goldfish does so for the same reasons. For one thing, the young of water fowl are fluffy and not as dependent on their mother. The young of cardinals, meanwhile, are naked, blind, and dependent on their mothers for a time. Thus, swans and ducks won't have the same reasons for reacting to open mouths that cardinals do.
Get weekly science updates in your inbox!