Justification of Red List Category
This species is listed as Endangered because it has a very small population. However, the conservation status of the species is improving, with not only increases in the natural wild population but also establishment of reintroduced flocks that may become self-sustaining. As a result, the number of mature individuals is continuing to increase and this species may merit downlisting to Vulnerable in the near future.
The total population in the wild numbers c.483 individuals. However, the only self-sustaining population breeding in Northwest Territories/Alberta, Canada and wintering in Texas, USA numbers 329 individuals, fewer than 250 of which are mature. Hence we retain a precautionary estimate of 50-249 mature individuals. Despite this however, the latest evidence from the Crane Conservation Strategy (Smith 2019) suggests that both the self-sustaining Aransas-Wood Buffalo population and additional reintroduced populations have increased notably in recent years and that the current population estimate may now be a considerable underestimate.
The natural flock has increased at 4.2% per year over the past 20 years, excluding the drop in 2009, slightly below the growth rate of 4.6% since 1938 (T. Stehn and J. Cannon in litt. 2007, Pearse et al. 2019). This equates to a rapid increase over the last three generations.
Grus americana declined from historic estimates of >10,000 prior to European settlement of North America to 1,300-1,400 birds by 1870, and only 15 adults in 1938 (CWS and USFWS 2007). As of 2016/17 there are four wild populations totalling c.483 individuals, including three reintroduced populations in the eastern U.S. that are not yet self-sustaining. The only natural wild population breeds in Wood Buffalo National Park, on the border of Northwest Territories and Alberta, Canada, and winters at and near to Aransas National Wildlife Refuge, Texas, U.S.A. (Meine and Archibald 1996) (although in 2011-2012 they were observed up to hundreds of kilometres away from here [Wright et al. 2014]). It totalled 266 birds in 2007 (T. Stehn in litt. 2007), with 65 active nests (B. Johns in litt. 2007), followed by a record 270 birds in spring 2008 (Archibald 2009), dropping to 247 in spring 2009 (Archibald 2009) following a drought in the wintering quarters in Texas. As of winter 2015-2016 this population contained 329 individuals, including 122 adult pairs (Butler and Harrell 2016). A reintroduced, non-migratory flock in Florida numbered c.41 individuals in 2007, but due to lack of reproductive success and high mortality rates this project was discontinued in 2007 (T. Stehn in litt. 2007, W. Harrell in litt. 2016). This population contains a dozen or less individuals (H. Ray in litt. 2016). A separate reintroduced flock migrates between Wisconsin and south-eastern USA. This population numbered 75 birds in 2007 (T. Stehn in litt. 2007), increasing to c.90 birds in 2008 (Stehn 2008), and as of January 2017 the population numbers 104 individuals (Whooping Crane Eastern Partnership 2017). The first wild born chick fledged in Wisconsin and migrated successfully in 2006 (T. Stehn in litt. 2007) and another wild born chick hatched in June 2009 (Garland and Peterson 2009). A new reintroduced flock comprising 10 juveniles was established in south-western Louisiana in early 2011 (Zimorski 2011), and this population now numbers 38 individuals (Department of Wildlife and Fisheries State of Louisiana 2017, H. Ray and W. Harrell in litt. 2016). Captive flocks totalled 151 birds in 2008 at 5 breeding centres and 6 display facilities in the USA and Canada (Stehn 2008). Overall, the global wild population has increased in numbers since 1938.
It breeds in prairie wetlands, preferring small, shallow lakes and ponds, willow communities, marshes, mudflats and perhaps sedge meadows, but this may be atypical considering its historical range (Archibald and Meine 1996, Timoney 1999). Eggs are laid from late April to mid-May (Archibald and Meine 1996). It winters in coastal brackish wetlands. For the wild population winter mortality appears to be correlated with blue crab availability at the Aransas National Wildlife Refuge, with higher mortality in years of lower crab abundance (Pugesek et al. 2013). The natural population are known to feed on beetles, crabs/crayfish, vegetation, seeds, molluscs and other vertebrates with introduced populations thought to feed on largely the same sources alongside benthic invertebrates, and amphibians and reptiles (Dinets 2016, Caven et al. 2019, Neri 2020). Stopover sites typically comprise wetland land-cover types and lowland grasslands (Baasch et al. 2019).
Over-hunting, habitat conversion and human disturbance were the main causes of the species's decline. Currently, the most significant known cause of death or injury to fledglings is collision with powerlines (Lewis 1997). Powerline markers can reduce collisions by 50-80%, but most powerlines remain unmarked and collision is a major and growing problem (Lewis 1997, Folk et al. 2013); 45 powerline collision-related mortalities were recorded between 1956-2006 (Stehn and Wassenich 2008, Smith 2019. The anticipated placement of thousands of wind turbines in the migration corridor will decrease availability of crane stopover habitat and may also dramatically increase the number of powerlines (T. Stehn in litt. 2007). Increases in the number of powerlines also stems from increased oil and gas exploration along parts of the species's migration corridor whilst activity and traffic associated with drilling may also be of significant detriment (Niemuth et al. 2018). In 2007, a lightning strike during severe weather killed 17 captive-bred young birds being housed in a top-netted release pen in Florida (T. Stehn in litt. 2007). Eggs and pre-fledged chicks are subject to predation by various birds and mammals including raven, bald eagle, wolf, black bear and lynx (CWS and USFWS 2007), while harassment of nesting individuals by parasites such as black flies can lead to nest abandonment, and this has been proposed as a key reason for failed breeding in one of the introduced populations (Runge et al. 2011, Barzen et al. 2018). Drought is a serious threat to the species as it is detrimental to all habitats utilized by this species, but is especially harmful by dramatically decreasing production on the nesting grounds (RENEW report 1999, Butler et al. 2014). In early 2009, a prolonged drought and reduced water inflow to coastal wetlands led to a reduction in availability of blue crabs Callinectes sapidus and wolfberries Lycium spp. (important food items), causing Whooping Crane mortality rates to double (Archibold 2009). Drought, and alteration and destruction of natural wetlands and rivers impacts roosting and foraging sites during migration (Niemuth et al. 2018, Baasch et al. 2019) whilst coastal development, sea level rise, climate change, chemical spills, reduced fresh water inflows, and human disturbance threaten the Texan wintering grounds (RENEW report 1999, CWS and USFWS 2007). Aransas National Wildlife Refuge (NWR) can only support a maximum of 500 birds through the winter (T. Stehn in litt. 2007) and falls short of the initial downlisting target of 1,000 birds. Continued population growth may force some cranes in future to use disturbed and suboptimal habitat (M. Reid in litt. 2003). Much of the currently unoccupied crane habitat at Aransas where the cranes would be expected to expand into is being threatened with construction of houses (T. Stehn, in litt. 2007). There are currently concerns about oil spills and river inflows to Aransas NWR (CWS and USFWS 2007), as well as reduced water flows in the central Platte River Ralley, Nebraska, a key stopover site for migrating Whooping Cranes (Chavez-Ramirez 2008). The spread of West Nile virus and avian influenza in the future may pose a threat to the species (Chu et al. 2003). The long-term effects of genetic drift after a severe population bottleneck are unknown (Glenn et al. 1999, Smith 2019) There have been incidences of illegal shooting of the species and it is known to be an increasing threat with 27 confirmed shooting mortalities between 1967 and 2016 (MacKenzie 2011, Shaw 2011, Condon et al. 2018, Niemuth et al. 2018, Smith 2019).
Conservation Actions Underway
CITES Appendix I and II. CMS Appendix II. A U.S. District Court has ruled to restrict water offtake from the Guadalupe River, Texas, as so much water was being taken it was a breach of the Endangered Species Act against this species (Beilfuss 2013). There is an international recovery plan (CWS and USFWS 2007) focusing on increasing the size of the natural flock, establishing additional wild populations through experimental releases, teaching captive-bred birds to migrate (Lewis 1995, Line 1995, RENEW report 1999), and increasing the captive population for experimental releases and ecological research (e.g. habitat selection). Considerable progress has been made in improving the genetic health of captive stock and in breeding under-represented genetic strains, but delayed reproduction in captivity and the failure of some pairs to breed at all has slowed down progress (Putman 2007). In the past, recruitment was increased in certain years in Canada by removal of a single egg from two-egg broods (Boyce et al. 2005); the removed eggs are used to supplement captive flocks, but the overall impact of the egg pickup program is largely undetermined (CWS and USFWS 2007). An eastern migratory population which mostly winters in Florida and summers in Wisconsin has now been established but only four instances of successful breeding has been recorded so far (J. Hook in litt. 2007, Garland and Peterson 2009, H. Ray in litt. 2016). If passed, the Crane Conservation Act (H.R. 1771 and S. 1048) would allocate $5 million per year over five years to be spent on crane conservation efforts world-wide, with strict limitations on the amount going to help Whooping Cranes. A process has been initiated as a collaborative project to conduct a Population Viability Analysis and a Population and Habitat Viability Assessment to aid in the recovery of this species (Harrell and Bidwell 2015).
132 cm. Large white crane. Adults white with red crown and black forehead, lores and moustache (tipped red), and red facial skin around large, horn-coloured bill. Shows black primaries in flight. Immature whitish with scattered brown feathers over wings and paler, reddish-brown head and neck. Similar spp Immature Sandhill Crane G. canadensis is smaller with grey basal colour. Voice Trumpeting ker-loo ker-lee-loo.
Text account compilers
Archibald, G., Benstead, P., Bird, J., Cannon, J., Derhé, M., Fasbender, P., Harding, M., Harrell, W., Hook, J., Isherwood, I., Johns, B., Pilgrim, J., Ray, H., Reid, M., Stehn, H., Stehn, T., Wege, D. & Westrip, J.R.S.
BirdLife International (2021) Species factsheet: Grus americana. Downloaded from http://www.birdlife.org on 16/05/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/05/2021.