One of the most aggressive birds you could meet... the truth about the friendly robin redbreast

Kung-fu robin: The robin sings to mark out its territory and is fiercely territorial and won't tolerate another robin on its turf
The robin is a bird you might think you know well...
Its public image is one of a tame, friendly bird, when in reality, it is one of the most aggressive birds you could meet! If you’re another robin that is. Robins are fiercely territorial throughout the year and will not tolerate another robin entering their patch of turf. And it’s not just the males. Females also defend a territory through autumn and winter. Unlike other bird species, both the males and females have red breast feathers, making them difficult to tell apart.