Blinded by love – some male pheasants restrict their sight in bid to impress females

Many animals try and win a mate by displaying spectacular ornamentation – like the famous tail of male peacocks. However, these impressive traits can have negative consequences, even hindering movement or making individuals easier for predators to find. New research has revealed a previously undocumented example of this: the feather ornamentation on the heads of male Chrysolophus pheasants restricts their field of view.

A golden pheasant

Image: Aflo Images

Just like us, animals have a field of view which dictates how widely they can see. Until now, there have been no significant differences in visual fields between sexes. However, for the first time ever, the new findings reveal that the cranial feathers of male golden (C. pictus) and Lady Amherst’s (C. amherstiae) pheasants are significantly worse than their female counterparts – impeding their ability to gather information from the world around them.

This effect is most extreme vertically, where males see 30° or 40° less in golden and Lady Amherst’s pheasants respectively. This difference was absent in two closely related species also measured in this study, silver pheasants (Lophura nycthemera) and green pheasants (Phasianus versicolor), making the finding pretty unique.

The researchers made this discovery by chance while investigating why some bird species are so prone to flying into anthropogenic objects such as wind turbines and power lines, while others spot the threat and take evasive action to avoid the collision. The aim is to use this information to design better mitigation strategies and patterns, to then go on to objects such as turbines, to reduce bird collisions. Senior researcher Dr Steve Portugal says:

“We know surprisingly little about how birds see the world. To get a good overview, we are measuring the visual fields of many bird species. These two were part of that, and that’s when we discovered this oddity.”

He adds:

“For the birds, it is a little bit like a trip to the opticians. They are held in place, and using an ophthalmoscope, we shine a light into their eyes, looking for flashback. This flashback is a little like what you see when driving at night and an animal is in the headlights. Through moving around the bird’s head – all around, up and over – you can measure the region around the head that the bird can see! Importantly, this quantifies three components of the visual field, the monocular region (where one eye can see), the binocular region (where both eyes can see), and the blind region (no eyes can see).”

Steve Portugal using an ophthalmoscope with a vulture

It is possible that this newly found trait may form part of the ideas of ‘handicap’. The idea is that exaggerated features are found attractive by females, as they suggest the male is ‘good quality’ as he is surviving and doing well despite having this handicap.

Why this strange trait has evolved in just these two species is not entirely clear. Steve says:

“One idea is that it’s perhaps to do with the habitat they live in. Both golden and Lady Amherst’s pheasants live in dense forest. Perhaps they can’t see very far anyway due to a cluttered environment of trees, shrubs and plants – making the consequences of their feathers not as significant as they otherwise might be.”

For their wider project on reducing bird collisions, Steve and his colleagues plan to look in more depth at how different species perceive and see objects ahead of them.

To read more about this research, published in Biology Letters, visit: https://royalsocietypublishing.org/doi/10.1098/rsbl.2025.0405