The scene looks like something out of a brutal fight: one flamingo drives its beak into another’s head while an intense red liquid falls directly onto a chick’s beak. Thousands of people on social media interpreted it as bleeding out, but no, it isn’t.
It is called crop milk, a thick and nutritious secretion that flamingos—males and females—produce in the lining of their crop, the same area where they process food. The hormone behind all this is prolactin, identical to the one that activates lactation in mammals. This substance is rich in protein, and its red color comes from the carotenoids in their diet, not from red blood cells.
But this incredible method comes at a price: throughout this time, the parents overfeed themselves to produce the crop milk, which not only nourishes the chicks but also helps them develop their characteristic color. The process is so exhausting and demanding that the male and female must take turns carrying it out, and both parents lose their color during this time.
And although they are not the only birds that feed their young with a similar secretion, the intense red color of flamingo milk makes the scene one of nature’s most bewildering.