When I visited the Monte Vista National Wildlife Refuge in Colorado these Yellow-headed Blackbirds were everywhere.
The breeding habitat of the Yellow-headed Blackbird is cattail marshes in North America, mainly west of the Great Lakes. During the breeding and nesting season the males are very territorial and spend much of their time perched on reed stalks and displaying or chasing off intruders.
This bird’s song resembles the grating of a rusty hinge. (Wikipedia)