| Summary: | 博士 === 國立成功大學 === 生命科學系碩博士班 === 95 === The Black-faced Spoonbill (Platalea minor) is a critically endangered species. About 50%~70% of individuals regularly winter on the southwestern coast of Taiwan. This study investigated the stomach contents of Black-faced Spoonbills killed by avian botulism between December 2002 and January 2003 to identify the food of this species at the wintering site. Fourteen fish species belonging to eight families and one species of prawn were retrieved from 43 stomachs. The Shannon-Weiner index for the diet was 1.90. The estimated mean total dry weight of contents per stomach containing animal items was 23.3 g (range, 0.1~111.7 g). The dogtooth-toxic goby (Yongeichthys caninus) was the most abundant diet species comprising 39% of the total diet items but contributing only 2% of the estimated total dry weight. The large-scale mullet (Chelon macrolepis), comprising only 17% of the total diet items but contributing 54% of the estimated total dry weight, was the most important diet species. Our results suggest that conservation of the large-scale mullet in the habitats is important to this endangered wader. This study also investigated the food resources of the Black-faced Spoonbill at Chiku Wetland from November 2003 to May 2004. In total, 70 fish species belonging to 33 families were collected. The most abundant fish species in those habitats was Leiognathus equulus (19.9%) followed by C. macrolepis (11.5%), C. alata (8.4%), Sillago sihama (7.8%), and L. bindus (5.6%), which together accounted for > 50% of the total number. These results indicate that the Chiku Wetland is an important foraging habitat for the wintering Black-faced Spoonbill. Over the past 15 years, the global population of the Black-faced Spoonbill has steadily increased. I estimated global population growth rates of the Black-faced Spoonbill based on annual counts of wintering populations in East Asia between 1991/1992 and 2003/2004. The mean global annual growth rate was 1.13 ± 0.08. The estimated survival rate was 86.6% ± 9.3% based on the annual return rates of color-banded birds in Taiwan between 1998 and 2005. I also predicted global Black-faced Spoonbill populations in 2003/2004~2013/2014 using a stochastic exponential model and showed the mean global population in 2013/2014 should exceed 4000 ± 950. The probability of a global population decline to less than the 2003/2004 level is low (p = 0.06). If the 1991~2004 growth rate is sustained, the probability for the global population to increase to twice that of the 2003/2004 level is 0.98 and the predicted mean wintering population in Taiwan could exceed 2000 in 2013/2014. Because the wintering population at Chiku Wetland is increasing, establishment of new protected areas in southwestern Taiwan will be necessary to ensure continued growth. Furthermore, maintaining sufficient quantities of fish in the existing reserves and adjacent fish ponds will be important to this endangered wader.
|
|---|
