100 pigeons and their diet

Due to a high degree of faunal and floral endemism oceanic island ecosystems are of high priority when it comes to biodiversity conservation. Evolution under isolated conditions formed unique ecosystems, but those are highly vulnerable to human disturbances, such as deforestation or the introduction of invasive species.

For example knowing the diet of an endangered animal might become very important for adequate restoration efforts on oceanic islands because introduced species may already be a major component of the diets of some endangered species.

The red-headed wood pigeon Columba janthina nitens is a critically endangered subspecies endemic to the Ogasawara Islands, a chain of oceanic islands located 1000 km south of the main islands of Japan. The current population of this species might only comprise of 100 individuals. Furthermore, the native forest of the Ogasawara Islands has been destroyed as a result of human settlements in the 19th century and World War II. As a result the islands are now home to several introduced plants which have expanded their natural range replacing the eradicated local flora. Researchers supected that the red-headed wood pigeon might have shifted its diet in favor of the introduced species in order to cope with the lack of native food resources. 

A group of Japanese colleagues went ahead and tested this assumption by using next-generation sequencing of fecal samples from the birds. They called it DNA Barcoding although they used a different marker (the chloroplast trnL P6 loop) for their analysis. It is not clear why this marker was chosen although it had been used for similar studies before.The disadvantage of using a non-standard becomes clear when reading their publication. In order to get some useful results they first had to construct their own library of reference sequences (over 200 species) before moving on to the fecal samples. Not only does that sound like a lot of extra work but for all other scientists following agreed upon standards this library is not very useful unless they shift their attention to trnL P6. I find this very frustrating as the study as such is great and the results very important for the planning of any restoration efforts:

In this study, a diet analysis using DNA barcoding provided a high-resolution identification of food plants and clearly overcame the bias of traditional microhistological analysis. The results of the DNA barcoding indicated frequent consumption of introduced species, rather than only native species, by the pigeons. The rapid eradication of some introduced species without restoration of the native seed plants may reduce available food resources for this pigeon. Thus, a strategy that balances the eradication of introduced plants and the restoration of native food resources is important. Differences between the composition of pigeon diets on Chichijima and those on Hahajima should also be considered during the restoration of each island. Although some existing technical problems must still be solved (e.g., the discrimination rate of the P6 loop database, sampling strategy), the NGS DNA barcoding approach will provide a better understanding of the food web, including the interactions between native and introduced species and appropriate nature restoration planning for oceanic island ecosystems.

Overall a great example showing the advantages of a deeper understanding of food webs provided through next generation sequencing. If it helps those birds even better. They just shouldn't call it DNA Barcoding because it isn't.