| The Crested Ibis (Nipponia nippon), is an endangered bird species of the world. During the past30years, a great deal of conservation effort both in-situ and ex-situ, has been successfully undertaken by researchers and Chinese government. The wild population has increased from seven to approximately1500:more than800wild individuals and700captive-bred individuals reside in eight protection centers located in China, Japan and Korea. The distribution range of wild population has increased from5km2to approximately6000km2. Once it comes down with the malignant incident, they will Probably bring the crushing consequence to wild population in existence, so it is extremely urgent to carry out a reintroduction program of the Crested Ibis, look for the suitable habitat, and establish the self-sustained population with genetic vigor in the historical habitats. The first reintroduction program of the Crested Ibis was established at Ningshan County in May2007. Until2012, the captive-bred individuals has increased to56,25adults were monitored in the wild,10pairs were formed,21clutches (66eggs) were produced and33nestlings had fledged successfully. The result means that the first reintroduction program in the world has achieved one of its first targets.In order to determine the population dynamics and habitat use of the post-fledging dispersal, In order to determine the population dynamics and habitat use of the post-fledging dispersal, and provide necessary theoretical and practical basis for Crested Ibis conservation, Dispersal patterns and habitat use were investigated by monitoring color-banded and by tracking radio-tagged birds from April2008to December2010, and the results have been showed as follows:Natal home ranges were occupied for an average of8.93±5.16days (n=15) from time of fledging (39-43days of age) to departure from the nest tree (roosting site). Movements of family groups prior to dispersal were centered on nest sites during the period, fledglings typically flew<100m and perched in oak-pine forest patches at the edge of open habitats. During this period, fledglings were still partially dependent upon parental care and were typically fed on a daily basis. A significant negative correlation was found between the number of days that juveniles remained at the natal sites for roosting and the mean distance from nest site to primary foraging grounds(Pearson r=-0.754, P=0.031, n=8). After11.5±3.5days (n=11), Siblings increasingly became independent of their parents by mid-August and then moved progressively farther from their natal home ranges to post-dispersal locations. Mean dispersal direction was204.4±SD of60.1°and a mean dispersal distance was11.3±3.5km (n=11). Hatch-year birds took75.2±39.5days (n=11) to disperse from their natal area to their post-dispersal locations.Distances of post-fledging dispersal among11nestlings was significantly different (t=6.31, df=10, P=0.000), ranged from1to118days; Speed of post-fledging dispersal was not significantly different (t=2.04, df=10, P=0.069), ranged from0.09to2.38km/d. In addition, distances of post-fledging dispersal was significantly different in different months (F=9.535, df=6, P=0.000), the minimum in July (1.95±1.21km), and the maximum in November (11.07±3.43km).During the period of postfledging dispersal, shallow rivers (48.36%)were used most around the dispersal period, and the proportion of time differed significantly (F=1.019, P=0.003), ranged from0(June and December) to66.7%±22.9%(September), and Paddy or lotus fields (40.44%) were another important selection, the proportion of time spent foraging in paddy fields differed significantly (two-way ANOVA:F34,2101.02, P=0.015), ranged from30.0%±3.2%(September) to100.0%±1.5%(December). Patches of Chinese Red Pine were primarily used by ibis fledglings for night roosting which was by far the most abundant habitat (54.96%) available to juveniles during the period of dispersal, ranged from30.0%±0.5%(June) to65.2%±4.3%(December).Roosting habitat selection is an important form of habitat use. Four main roosting sites were used along river with the southwest direction. Of11tracked fledglings, five individuals used three roosting sites; four individuals used four roosting sites; and two individuals separately used two and one roosting sites.The number of biggest cluster in different years was not significantly different (F=0.416, P=0.673, df=2), but contrarily in different months (F=4.041, P=0.040, df=5). Roosting habitat selection during three years was not significantly different for all the reintroduction individuals (F=0.040, df=2, P=0.961), but contrarily for the nestlings (F=3.324, df=2, P=0.043). Roosting habitat selection during different months (July-December) was not significantly different for all the reintroduction individuals (F=1.519, df=5, P=0.199), and similarly for the nestlings (F=1.053, df=5, P=0.397). Habitat selections of the four roosting sites for nestlings and all individuals were both significantly different (F=4.354, df=3, P=0.008; F=20.154, df=3,P=0.000).At present, there are three main seasons for explaining post-fledging dispersal: inbreeding avoidance hypothesis, competition avoidance hypothesis and changing the breeding locations hypothesis. Increase in food availability seems to be the proximate factor resulting in post-fledging dispersal, but the ultimate factor may be that the fall/winter flocking period can provide the opportunity to interact with possible mates and appears to be very important for persistence of the surviving population.Although the wild birds dispersed approximately twice as far as the released individuals, and the dispersal directions were also different, but the overall pattern and behavior characteristics of post-fledging dispersal is similar between the reintroduced and wild population. |
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