Justification of Red List Category
This species has experienced a long term population decline which has been rapid during the past decade. For this reason it is currently classified as Vulnerable. More accurate survey data may warrant a re-evaluation of its status.
The population is estimated to number anywhere between 0.2-2 million individuals (R. Greenberg in litt. 2006).
Two sources provide quantitative estimates of decline for the species: Breeding Bird Survey (BBS) and Christmas Bird Counts (CBC). Sauer et al. (2005) provide an estimate for annual declines for a 39 year period of 12.5% per year, derived from BBS data. The estimated trend for the period 1996-2005 is a 1.8% decline per year, equating to a 16.6% decline over ten years. The CBC returns an estimated global decline for this period of 5.1% per year (CI = 2.4- 6.7%) which corresponds to a decline of 40.8% over the past decade. Interpreting the two estimates, the population is believed to have declined by >30% over the past ten years (R. Greenberg in litt. 2006). Butcher and Niven (2007) also combined data from the two sources, estimating a large and statistically significant population decrease over the last 40 years in North America (83.8% decline over 40 years, equating to a 36.6% decline per decade).
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 United States. 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.
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.
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), mortality associated with past and ongoing blackbird control efforts (Greenberg et al. 2011), and potential low level mortality as a result of collisions with communication towers (Longcore et al. 2013).
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.
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.
Text account compilers
Bird, J., Ekstrom, J., Westrip, J., Butchart, S., Derhé, M.
McClure, C., Greenberg, R., Butcher, G., Luepold, S., Wells, J.
BirdLife International (2020) Species factsheet: Euphagus carolinus. Downloaded from http://www.birdlife.org on 25/09/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 25/09/2020.