Novel foraging by wintering Siberian CranesLeucogeranus leucogeranusat China’s Poyang Lake indicates broader changes in the ecosystem and raises new challenges for a critically endangered species

Abstract

SummaryFollowing an abnormal flood in 2010 at China’s Poyang Lake, we observed wintering Siberian Cranes Leucogeranus leucogeranus switch from foraging in the shallow-water wetlands they typically use to grassland habitats. These previously undocumented habitat selection patterns raised questions whether differences in crane behaviour such as foraging success existed between the two habitats and how those differences might affect this critically endangered species. Over two winters, we used the density of customary food items (tubers of Vallisneria spp.) obtained from long-term monitoring efforts, Siberian Cranes flock behaviours, individual foraging success and estimated total flock foraging effort across both habitats. Novel foraging patterns by Siberian Cranes were associated with low densities of Vallisneria tubers across multiple sub-lakes within Poyang Lake National Nature Reserve (PLNR). Foraging success was higher in grasslands than in wetlands in winter 2010–2011, but higher in wetlands following a recovery of Vallisneria in 2011–2012. Subsequent to upland foraging during the winter of 2010–2011, we observed lower juvenile to adult ratio of Siberian Cranes at a fall migratory stopover location in north-eastern China despite indications of average environmental conditions in the nesting areas from 2010 to 2012. While grasslands adjacent to shallow-water habitats may be important refugia for wintering Siberian Cranes when Vallisneria is absent or inaccessible, and should be included in protected areas, multi-year dependence on grasslands for foraging could negatively impact population levels. Eliminating crab farming in protected areas and extending protection to shallow water areas sheltered from flooding by dykes could also help secure high quality foraging habitat under a variety of hydrological regimes. Novel foraging patterns by wintering Siberian Cranes represent a new challenge to the conservation efforts for this species that focus on shallow-water wetlands, and may be indicative of broader changes within Poyang’s ecosystem.

Drivers of a habitat shift by critically endangered Siberian cranes: Evidence from long‐term data

“…Waterbirds are expected to give up a foraging site when food density drops below a threshold value, and this giving‐up density threshold has been reported in many waterbirds (Jonzen, Nolet, Santamaria, & Svensson, 2002; Nolet et al., 2001; Sponberg & Lodge, 2005). The tuber collapse in the winter of 2010 was suggested to be a major driver for Siberian cranes moving from shallow waters to grasslands at Poyang Lake in that winter (Burnham et al., 2017; Jia et al., 2013). The decline of Siberian cranes in natural wetlands in winter 2012 was coincident with a tuber decline.…”

“…However, in the winter of 2010 (2010/2011), large numbers of cranes were observed, for the first time, foraging in grasslands on the roots of Potentilla limprichtii and bulbs of Tulipa edulis (Burnham et al., 2017; Jia et al., 2013). A flood‐induced food collapse was proposed to be the main driver of the habitat and diet shift (Burnham et al., 2017; Jia et al., 2013). The diet shift may have influenced the Siberian crane behavior and energy stores, possibly resulting in lower breeding success in the next breeding season (Burnham et al., 2017).…”

“…A flood‐induced food collapse was proposed to be the main driver of the habitat and diet shift (Burnham et al., 2017; Jia et al., 2013). The diet shift may have influenced the Siberian crane behavior and energy stores, possibly resulting in lower breeding success in the next breeding season (Burnham et al., 2017). Siberian cranes at Poyang Lake largely returned to shallow waters in the next winter when tuber abundance rebounded (Burnham et al., 2017).…”

Behavioural plasticity and trophic niche shift: How wintering geese respond to habitat alteration

“…While wild animals have been subjected to environmental disturbances during their evolutionary history and have evolved to match physiology and behaviour to the predictable environmental variations in their natural habitats (Schmidt-Nielsen, 1997), the accelerated rate of humaninduced changes, such as habitat modification and invasive species, poses a challenge for many taxa (Sih, 2013;Tuomainen & Candolin, 2011). For many animals, a change in behaviour, such as using alternative habitats (Basille et al, 2013;Burnham et al, 2017) and becoming more vigilant , is often the first response to anthropogenic disturbance (Tuomainen & Candolin, 2011;Wong & Candolin, 2015). Such behavioural flexibility, i.e.…”

“…However, flow regulation is ubiquitous in large river systems around the world (Best, 2019;Dudgeon et al, 2006). River regulations can degrade habitats (Dudgeon et al, 2006) and reduce food abundance, availability, and accessibility (Wang et al, 2013), leading to shifts in foraging behaviour (Burnham et al, 2017;McKnight, 1998;Stillman et al, 2015).…”