Abstract
The foraging ecology of pelagic seabirds is difficult to characterize because of their large foraging areas. In the face of this difficulty, DNA metabarcoding may be a useful approach to analyze diet compositions and foraging behaviors. Using this approach, we investigated the diet composition and its seasonal variation of a common seabird species on the Ogasawara Islands, Japan: the wedge-tailed shearwater Ardenna pacifica. We collected fecal samples during the prebreeding (N = 73) and rearing (N = 96) periods. The diet composition of wedge-tailed shearwater was analyzed by Ion Torrent sequencing using two universal polymerase chain reaction primers for the 12S and 16S mitochondrial DNA regions that targeted vertebrates and mollusks, respectively. The results of a BLAST search of obtained sequences detected 31 and 1 vertebrate and mollusk taxa, respectively. The results of the diet composition analysis showed that wedge-tailed shearwaters frequently consumed deep-sea fishes throughout the sampling season, indicating the importance of these fishes as a stable food resource. However, there was a marked seasonal shift in diet, which may reflect seasonal changes in food resource availability and wedge-tailed shearwater foraging behavior. The collected data regarding the shearwater diet may be useful for in situ conservation efforts. Future research that combines DNA metabarcoding with other tools, such as data logging, may provide further insight into the foraging ecology of pelagic seabirds.
Highlights
Seabirds are critical organisms within marine ecosystems as they are top-order predators in hierarchical food webs
Using a DNA metabarcoding approach, we investigated the dietary composition of the wedge-tailed shearwater during the prebreeding and rearing periods to compensate for the deficiency of the current knowledge of shearwater diet during the prebreeding period and its seasonal dietary shifts
In the 12S region, the assigned operational taxonomic units (OTUs) were taxonomically separated into 25 genera, four families, one order, and one superorder of prey fishes (Table 2)
Summary
Seabirds are critical organisms within marine ecosystems as they are top-order predators in hierarchical food webs. DNA metabarcoding of fecal samples is a noninvasive and sensitive method for identifying prey taxa [8,9]. This method does not place stress on the animals to determine their stomach contents; the metabarcoding method requires less effort than conventional morphological analyses [7]. With the development of high-throughput sequencing techniques, it is possible to recover DNA sequences from fecal samples relatively [10,11] In recent years, this method has been mainly used in dietary studies of large terrestrial mammals [12]. Continuous dietary research that applies noninvasive and sensitive DNA metabarcoding to seabirds is likely to be useful for monitoring marine ecosystems with very little impact on birds. Only a few such studies have targeted marine animals, such as penguins and seals [13,14], and only a limited number of Procellariidae species have been examined using DNA metabarcoding [15,16,17,18]
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