The much maligned Brown-headed Cowbird.
Rondeau Provincial Park, Ontario, Canada, June 29, 2020. Molothrus ater Females forgo building nests and instead put all their energy into producing eggs, sometimes more than three dozen a summer. These they lay in the nests of other birds, abandoning their young to foster parents, usually at the expense of at least some of the host’s own chicks. Once confined to the open grasslands of middle North America, cowbirds have surged in numbers and range as humans built towns and cleared woods. source - https://www.allaboutbirds.org/guide/Brown-headed_Cowbird/