The robin’s distinctive red breast is a beautiful sight as it’s seen against a backdrop of fresh snow. It’s actually a tool in their ongoing campaign to gain or retain territory, according to research from the University of Cambridge. For each year that passes, a male’s red breast gets a little larger.
Robins do not typically die of old age, so every year a robin survives is a credit to its survival skills. Following this logic, an older robin with a large red breast is a real threat, as his survival skills must be very well honed. Such a robin could therefore use his breast to attract mates, or to intimidate younger birds in battles over territory.