| Summary: | 碩士 === 國立臺灣大學 === 生態學與演化生物學研究所 === 101 === Waterbirds are one of the important natural resources of Tamsui River. There have been many studies focusing on short-term population change of them, mostly based on
single sample site. Those studies suggested that pollution and terrestrialization might be the causes of population decline. But population trends of migratory waterbirds are
affacted by both local and global factors, it should be verified in the first step. Besides, the trend within a single site doesn''t represent the situation of the whole Tamsui River.
Therefore, this study regards the populations at downstream of Tamsui River as one community, constructs long-term population trends, and explains the interspecies differences of population trends by biological traits. The data of waterbirds in wintering season (Nov. to next Feb.) are collected from 1991 to 1995, in 1997, 1999, and 2011, covering 9 sample sites. The long-term population trends of 20 years of 27 common species are constructed using poisson
regression log-linear model. Then univariate and multivariate analysis are conducted between population trends and 7 biological traits, related to habitat preference, food preference, and global factors, identifying the biological traits that better explain population trends. The study also replicates the analyses on the scale of individual sample sites, attempting to find out the differences between different study scales.
In the results, most of the long-term population trends of 27 common species are positive, 10 species have significantly increased (P < 0.05), only 2 species, common teal and black-headed gull have significant decreased. The results on the sample-site scale indicate the Guan Du and Lu Zhou support more waterbirds now, but most populations in other sample sites have decreased in the past 20 years. Among all biological traits, food preference explains the population trends best. Compared to food generalists, relying on both coastal and freshwater habitats, the species depending only on coastal habitats have more negative population trends. The study As to global factors, including global population trend, wintering location, breeding location, and habitat preference in breeding location, can''t well explain the trend in Tamsui River.
This study is the first one which constructs the 20-years-long population trends of waterbirds in Tamsui River. It also provides suggestion for monitoring those species that are food specialists or coastal-habitats-dependent in the future. Besides, the methods of this study can be applied to those studies focusing on waterbird populations of Taiwan.
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