Iridescent bird feathers. (1 Viewer)

Why did some bird species develop Iridescent feathers .. particularly birds of the Corvidae family as well as some dark colored Icterids such as the various Blackbird species?
What are the benefits of such a coloration?
It's very interesting that it seems to be more prevalent in the scavenger type of birds.

Although not an answer to your questions, you might find this short description of Birds' colour vision and colours interesting. Basically, we see very little of what a bird sees, so what is colourful to us might be dull to birds, and vice versa. Although I'd guess it's all related to hiding from predators or attracting a mate... or maybe it's "pretty" to us and means nothing to them.

There's a lot more info online about Birds' vision...

A lot of it is related to display and indication of condition - healthier individuals in better condition produce more of the preen oils that enhance iridescence. So it's a way of showing you're good.

It isn't more prevalent in scavengers, it is widespread among numerous groups of birds. Just a few examples:
Insect eaters:
https://www.birdforum.net/opus/Barn_Swallow
Nectar feeders:
https://www.birdforum.net/opus/Purple_Sunbird
https://www.birdforum.net/opus/Ruby-throated_Hummingbird
Ducks:
https://www.birdforum.net/opus/Mallard
And many more!