Rusty Blackbird decline has no single cause

Citizen-science data has revealed that Rusty Blackbird is among North America's most sharply declining songbirds.

Between 85% and 99% of the Rusty Blackbird population was lost in the 40 years to 2010, though the challenge of identifying the species among gatherings of other blackbirds has made it a particularly difficult bird to monitor.

Rusty Blackbird is a tough species to monitor due to its movements and similarity to other blackbird species (Steve Bell).

Data from the Christmas Bird Count, a long-running winter citizen-science survey in North America, eventually laid bare the steep decline, prompting further research into the continent's Rusty Blackbird population.

Rusty Blackbird favours wet, often beaver-influenced, forests across Alaska, Canada and northern parts of the US, breeding further north than any other American blackbird species.

Based on current understanding of its population, the species is listed as Vulnerable by the International Union for the Conservation of Nature (IUCN), while Partners in Flight warns that it is a "common bird in steep decline."

There is currently no clear single explanation for the plummeting Rusty Blackbird numbers, though it is thought that drying wetlands, timber harvesting, argriculture and pollution are thought to be contributing to the decline in tandem. Due to its similarity to closely related species, it is possible that Rusty Blackbirds have been shot and poisoned accidentally during culling for programmes controlling other blackbird species.

In its wintering range in the eastern US, around 80% of lowland hardwood forests have given over to farmland.

Researchers have called for a specific monitoring scheme in the Adirondack Wetlands is needed to assess the decline in this key area for the species. They have said that it it were not "just another blackbird", there it might have already been afforded a state-sponsored monitoring programme.