Abstract:

Objective: The purpose of the present study was to explore the foraging strategies of oriental storks ( Ciconia boyciana ) under different conditions, and their population distribution in two areas of Poyang Lake, so as to provide a theoretical basis for the protection of this species. Method: From December 2021 to March 2022, the foraging behavior of oriental storks in Poyang Lake National Nature Reserve and Wuxing Siberian Crane Conservation District was observed using the focal animal observation method. In 2015–2021 and 2012–2022, the population of oriental storks in East Poyang Lake National Wetland Park (PLNWP) and Nanji Wetland National Nature Reserve (NWNNR) at Poyang Lake was investigated in January of each year. Result: The mean water depth of oriental storks habitat was (17.22 ± 6.28) cm (n = 754). The water depths in level III and level II were the most common depth used by oriental storks, accounting for 51.33% and 35.94%, respectively. The storks’ foraging water depth was (14.64 ± 6.26) cm (n = 669), and the main water depths were H3 and H2, accounting for 43.20% and 37.52%, respectively. The foraging frequency was (6.58 ± 3.13) times·min^?1 (n = 334), the success foraging frequency was (0.2 ± 0.53) times·min^?1 (n = 334), the success rate of foraging was (3.36 ± 9.55)% (n = 334), and the step frequency was (20.15 ± 11.49) steps·min^?1 (n = 334). The step frequency at water depth I was significantly higher than that at water depth II ( P < 0.001), III ( P < 0.001), and IV ( P = 0.006), and the foraging frequency at water depth III was significantly higher than that at water depth I (P = 0.038). The step frequency in the morning was significantly lower than that at noon ( P < 0.001) and in the afternoon ( P < 0.001), and the step frequency at noon was significantly higher than that in the afternoon ( P = 0.017). The success foraging frequency ( P = 0.005) and success rate ( P= 0.006) in the afternoon were significantly higher than those at noon. The step frequency showed a highly significant negative correlation with water depth ( P< 0.001), and foraging frequency showed a highly significant positive correlation with water depth (P = 0.004). A total of 979 stork-time were recorded in PLNWP from 2015 to 2021, and 5 233 stork-time were recorded in NWNNR from 2012 to 2022. The population size of storks in NWNNR was greater and more stable than those in PLNWP. In PLNWP, the storks were mainly distributed in Niejia and Hanchihunan, and in NWNNR, they were mainly distributed at Sanhu Lake and Changhu Lake. Conclusions: Foraging parameters of Oriental Storks were different at different water depths an Foraging parameters of oriental storks are different at different water depths and periods. The results have demonstrated that the storks can adapt their foraging strategies quickly and flexibly depending on environmental variables such as water depth and period of time to guarantee that they obtain sufficient energy. The storks tend to have a concentrated distribution pattern in PLNWP and NWNNR and exhibit high requirements for its habitat environment. NWNNR can provide a stable habitat and foraging environment for this species; therefore, this site is of great significance for its protection.

Key words: foraging behavior, Oriental Stork, population dynamics, Poyang Lake