Habitat Selection And Carrying Capacity Analysis Of Breeding Oriental White Stork (Ciconia Boyciana) In The Yellow River Delta

As a threatened large wading bird, the oriental white stork (Ciconia boyciana) is classified as endangered species by IUCN. Its population size is estimated less than 3000. In recent years, it was reported that the breeding areas of oriental white stork to expand in the migration stopover sites and wintering areas continually. As one of the most important migration stopover site of oriental white stork, the Yellow River Delta region maintained a breeding population that has gradually formed a stable breeding population in recent years. It was significant for the conservation of the species and the management of the Yellow River Delta Nature Reserve to understand how the breeding population utilized the habitat resources and how many breeding pairs the region could stay there for succeed breeding.Habitat resources were investigated by field work supported by remote sensing maps in the Yellow River Delta Nature Reserve during February to July 2010. Route survey method was utilized to investigate the situation of production and utilization of various types of habitats. Sampling method was utilized to investigate the foraging microhabitat and analyzing the ecological factors that affect the habitat selection and foraging.The minimum areas necessary for foraging of oriental white stork and the available foraging areas in Yellow River Delta were investigated during the breeding season. Habitat utilization of the oriental white stork was also investigated to get the optimal foraging area (the utilization coefficient i) Using the formula K=(S/s)/i estimated the space carrying capacity of oriental white stork in the Yellow River Delta Nature Reserve.A total number of 28 pairs oriental white stork bred there in 2010. Only 22 pairs of the 28 breeding pairs bred successfully with 73 eggs hatched and 65 nestlings survived to fledging. The breeding situation is more significant growth compare with previous years. The Habitat Preference Index (Pi) of the 11 major habitat types showed the oriental white stork favorite habitat type was the reed wetland (7.509) and shallow water wetlands (7.460). The oriental white stork was prefer to the reaped reed wetland in the early breeding period and the shallow water wetland was selected firstly in the last breeding period. The oriental white stork preferred to select the habitat where water area ratio were greater than 75%, water depth between 5 and 15cm, low vegetation height and small vegetation coverage, the distance from road between 500 and 1000m, near the nest and the hidden objects. The habitat where water area ratio less than 50%, water depth less than 5cm, high vegetation height and large vegetation coverage, the distance from road too near, far from the nest and the hidden objects were not selected. Hydrological factors, vegetation factor, disturbance factors were the main ecological factors that affected the foraging habitat selection of oriental white stork.Nearly half of the individuals (45.45%) generated alert or escape behavior to disturbance in the early breeding period, but the proportion dropped to less than 15% in the last breeding period. The oriental white stork increased tolerance to disturbance in the last breeding period. Levels of foraging effort were different in different breeding period and at different habitats. Differences of foraging displacement distance was significant between early breeding period (69.67±47.60m, n=30) and last breeding period (165.22±140.90m, n=23) (Independent samples t-est: t=-3.119, P=0.004,α=0.01). It was also significant between shallow water wetland (179.35±134.81m, n=23) and reaped reed wetland (60.17±33.21m, n=29) (Independent samples t-test: t=-4.141, P=0.000, a=0.01). Differences of foraging duration reached statistical significance between early breeding period (69.67±47.60m, n=30) and last breeding period (32.57±17.31min, n=23) (Independent samples t-test: t=-2.110, P=0.042,α=0.05). Differences of foraging duration was also reached statistical significance between shallow water wetland (33.91±16.27min, n=23) and reaped reed wetland (23.13±11.91min, n=29) (Independent samples t-test: t=-2.661, P=0.011,α=0.05).The daily foraging time of oriental white stork in nesting-hatching period was less than the parent care period significantly. Foraging activity was low in 9:00-11:00 during nesting-hatching period.There was suitable foraging habitat area 63.74km2 for oriental white stork in the early period, but the area dropped to 24.45km2 in the last breeding period. Habitat quality changed significantly during the breeding season and the suitable habitat reduced observably in the last breeding period. According to the estimate result, the nature reserve can accommodate 333 pairs of oriental white storks in the early breeding period and 79 pairs in the last breeding period.