The relationship between seasonal water level fluctuation and habitat availability for wintering waterbirds at Shengjin Lake, China

Abstract

SummaryConservation plans for waterbirds in periodically flooded wetlands should be based on a deep understanding of the relationship between habitat availability and the hydrological regime. Using waterbird surveys and remotely sensed images, we investigated how habitat availability for wintering waterbirds was regulated by seasonal water level fluctuation at Shengjin Lake in the lower Yangtze River floodplain, which is an important wintering area along the East Asian-Australasian Flyway. We recorded 52 waterbird species during three field surveys, and categorised them into four groups based on their foraging preferences: grassland, mudflats, shallow water, or deep water. Habitat availability for the four groups was significantly influenced by fluctuations in water level. Habitat for deep-water feeders dominated the lake throughout the year, despite contracting during the wintering season. Water recession during winter exposed more diverse riparian habitats that showed high spatial heterogeneity at the landscape level, with the Upper Lake providing the most suitable habitats for the most diverse and abundant waterbirds. It is worth noting that the water level was regulated highly for aquaculture during the early wintering period, impeding access to suitable habitats for the early-arriving waterbirds that foraged in the riparian mudflats and grassland. Furthermore, rapid water recession from the opening of a sluice gate allowed the exposed moist mudflats to dry up quickly, reducing its suitability for shorebirds and cranes. For effective wintering waterbird conservation in the ephemeral lacustrine wetlands in the Yangtze River floodplain, we suggest stepwise water recession plans, together with the recovery of the aquatic vegetation community and reduction in high-density aquaculture, to synchronise the exposure of foraging habitats with the migration phenology of different waterbird species.

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

“…agricultural habitats, food shortage, Leucogeranus leucogeranus, submerged plants, Yangtze River F I G U R E 1 Siberian cranes fed in rice paddies. The photo was taken by Lanhua Wang at Chengxin Farmland, Nanchang City, on 12 February 2017 large areas normally supporting more waterbirds than smaller areas (Li, Yang, et al, 2019;Roshier, Robertson, & Kingsford, 2002).…”

“…It directly determines the food accessibility for waterbirds because of the restrictions of bird morphology, such as the lengths of tarsometatarsi and necks. Areas of suitable habitats also influence waterbird distribution and abundance, with large areas normally supporting more waterbirds than smaller areas (Li, Yang, et al, 2019; Roshier, Robertson, & Kingsford, 2002).…”

Habitat Suitability Assessment of Wintering Herbivorous Anseriformes in Poyang Lake, China

“…The transition matrix (Table 4) shows only 23% of good grade areas remained unchanged, and the highest portion was changed to fair grade (58%). This habitat suitability change could be associated with differences in the area's hydrological fluctuation [85,86].…”

Flexible Foraging Response of Wintering Hooded Cranes (Grus monacha) to Food Availability in the Lakes of the Yangtze River Floodplain, China

“…The average annual temperature is 14-18°C, and the average annual rainfall is approximately 1000-1400 mm. Total variation in the extent of water at Shengjin Lake ranges from 140 km 2 during the summer wet season to 75 km 2 in the dry winter, resulting in the exposure of large areas of mudflats and small meadows of less than 20 km 2 , which provide suitable habitat for cranes [19,39,42,44]. Caizi Lake covers an area of 226 km 2 in summer when water levels peak at 14.88 m and covers 114.97 km 2 in winter when the water level drops to 10.63 m [41,45].…”

“…Given these constraints, animals have likely developed flexible foraging strategies to optimize the benefits of foraging to facilitate survival, and they are able to respond to the complex environment in a timely manner and adjust their foraging behavior to attempt to consume food resources that offer the greatest energy gain at the least cost [13][14][15]. Waterbirds, in particular, must display flexibility due to the constantly changing water levels of wetlands, as well as the management of agricultural lands (such as paddies) [13,[16][17][18][19][20]. Migratory waterbirds display flexibility in foraging behaviors, e.g., dunlin have changed their foraging mode, as well as morphological and digestive strategies, in response to changes in environmental conditions [21,22].…”