And the light-collared?

But what about that light-collared male, the one in the background? The lighter males have no territories of their own; instead, they stay on the territories of dark-collared males. Why isn't he chased off?

Dominance

If a dark-collared male has one or more light-collared males on his territory, he is able to attract more females. In this way, he will attain a greater number of matings. Dark males dominate light-collared males and prevent them from mating with the females.

Risky

The strategy is risky– if the dark male is busy fighting, the light male can quickly mate with a female! This only takes a second!

Competition

The only way for the light-collared male to mate is to wait patiently for an opportunity to arise. Despite this competition for females, the dark-collared male benefits in the long run from the presence of lighter males on his territory, because it enables him to attract more females.