VU
Rusty Blackbird Euphagus carolinus



Justification

Justification of Red List Category
This species has experienced a long term population decline which is thought to be rapid and ongoing. For this reason it is currently classified as Vulnerable. More accurate survey data may warrant a re-evaluation of its status.

Population justification
The population is estimated to number anywhere between 0.2-2 million individuals (R. Greenberg in litt. 2006, Scarl 2013), although a lack of accurate population surveys render this estimate highly uncertain. Further research to accurately quantify this species's population size is a pressing requirement.

Trend justification
The Christmas Bird Count currently estimates population declines of ~4.61% per year for E. carolinus throughout Canada, where the majority of this species's breeding range lies; equable to a ~37.6% decline over the stipulated ten year period (Meehan et al. 2018). Declines in the USA are however, estimated to be lower, just ~1.46% per year, or 13.7% over ten years. This is reflected in the Partners in Flight (2019) estimated rate of annual decline of ~2.50%, or 22.4% across the decade. Accurate quantitative estimates of this species's population size and trends are difficult to come by, therefore by interpreting the above estimates, it is tentatively assumed that E. carolinus is declining at a rate in excess of >30% per decade due to the high rates of past decline and rapid reductions currently ongoing throughout its breeding range. More accurate quantification of such trends should constitute an urgent research priority however.

Distribution and population

Euphagus carolinus has a large range, breeding across the boreal zone of North America from New England, through Canada to Alaska and winters widely across the south-eastern U.S.A.. The population was estimated at 2 million individuals based on data from the North American Breeding Bird Survey collected during the 1980s and 1990s. This figure is now likely to be a considerable overestimate as the species continues to decline, and a recent study only found the species at <10% of sites (Scarl 2013). Estimates of the global decline since 1966 vary between 85% and 99%. This ongoing decline follows a longer term decline that began prior to 1950. The reasons for this dramatic decline remain poorly understood.

Ecology

It breeds in boreal wetlands, primarily around ponds and streams within the boreal forest (see Powell et al. 2014). It winters primarily in wooded wetlands and is not strongly associated with open agricultural habitats. Large flocks have been known to gather in suburban areas during wintering periods (Newell Wohner et al. 2018).

Threats

The reasons behind current trends are poorly understood but several threats are suspected to be causing the declines. The destruction and conversion of boreal wetlands (predominantly in the southern boreal forests) is a significant threat to the species. Strip-mining for tar sands is expected to increase in the future, with up to 300,000 ha of Canada's boreal forest and wetland predicted to be directly affected over the next 30 to 50 years (Wells et al. 2008). Other possible threats include boreal wetland drying and chemical change resulting from global climate change (Matsuoka et al. 2010, McClure et al. 2012), depletion of available calcium resulting from acid precipitation (Greenberg and Droege 1999, Greenberg et al. 2011), increase in methyl mercury (Greenberg et al. 2011, Edmonds et al. 2012), disease (Barnard et al. 2010), loss of boreal forest habitat due to hydropower development (S. Luepold in litt. 2016), loss of wooded wetlands in the south-east U.S. winter range (Hamel et al. 2009, Greenberg et al. 2011), and mortality associated with past and ongoing blackbird control efforts (Greenberg et al. 2011). Recent research suggests that an ecological trap created through timber harvesting and clear-cutting on breeding grounds may be responsible for declines, possibly through increased Red squirrel (Tamiascirius hudsonicus) nest predation, however evidence of such a trap is largely lacking (Buckley Luepold et al. 2015). Forest loss within the species's range is currently estimated at ~5.4% across the stipulated ten year period (Tracewski et al. 2016). Potential low level mortality may also result from collisions with communication towers (Longcore et al. 2013).

Conservation actions

Conservation Actions Underway
The species is not currently listed under the United States Endangered Species Act, but it is listed as a "Species of Special Concern" or "Threatened" or "Endangered" in several states (S. Luepold in litt. 2016). There is an International Rusty Blackbird Technical Group set up to research trends, threats and actions for this species.

Conservation Actions Proposed
Quantify the overall population size and trend. Identify the reasons behind long-term declines. Devise suitable actions to reverse declines. Consider listing under US Endangered Species Act. Protect suitable habitat.

Identification

A medium-sized blackbird with a square-tipped tail and thick bill. Males are entirely black, faintly glossed greenish. The eye is yellow. Females are dark grey-black and lack the glossy sheen of males. Immature birds are brown with a paler supercilium, darker wings and tail and some dark barring on males. Similar spp. very similar to Brewer's Blackbird Euphagus cyanocephalus, but males of that species have a blue body gloss with contrasting violet head and females are browner. Also structurally, rusty blackbird has a finer bill and less elegant gait. Voice Males sing a squeaky but sweet rising kush-a-lee.

Acknowledgements

Text account compilers
Everest, J.

Contributors
Bird, J., Butchart, S., Butcher, G., Derhé, M., Ekstrom, J., Greenberg, R., Luepold, S., McClure, C., Wells, J. & Westrip, J.R.S.


Recommended citation
BirdLife International (2022) Species factsheet: Euphagus carolinus. Downloaded from http://www.birdlife.org on 20/01/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/01/2022.