New Bird Species Discovered in Collections: A Tawi-Tawi Tale of Mismatched Specimens
The Delaware Museum of Nature and Science (DelMNS) houses an expansive bird collection in its Collections & Research Division, with over 116,000 bird specimens and 37,000 egg clutches, which are used for both scientific research and education. This collection is managed by DelMNS Research Director and Curator Dr. Matthew Halley, who has worked full-time at the museum since June 2021.
Last year, Dr. Halley encountered something that made him take pause: a single white-throated specimen in a drawer of brown-throated Pink-bellied Imperial Pigeon specimens (Ducula poliocephala) from the Philippines. The peculiar white-throated specimen was collected on Tawi-Tawi Island in 1971 by Dioscoro S. Rabor.
In a paper published in the Bulletin of the British Ornithologists’ Club, Dr. Halley has designated this specimen (DMNH 14999) as the “holotype” of a new species—the Tawi-Tawi Imperial Pigeon (Ducula tawitawi)—the first new (living) species of imperial pigeon to be described to science since 1928.
Species in the genus Ducula (family Columbidae) are commonly known as “imperial pigeons.” They live in the rainforest canopy throughout the Indo-Pacific region, and can reach considerable sizes (35–45 cm). Because their diet primarily consists of fruit, they likely play an important role as seed dispersers in tropical forests.
The last living Ducula species was described in 1928, nearly a century ago, and before that, it was 1896. For decades, it has been assumed that the scientific inventory of the world’s Ducula species was complete—until now. Unfortunately, around 20% of the ~353 species of pigeons and doves are threatened with extinction, and we can probably add D. tawitawi to the list. It is only found in the threatened rainforests of Tawi-Tawi, a single oceanic island.
Dr. Halley searched through museum databases to locate other Imperial Pigeon specimens from Tawi-Tawi, and contacted colleagues at the Philippine National Museum in Manila, but he only managed to locate two others—both in the Smithsonian National Museum of Natural History (USNM). They were collected during the Menage Expedition in 1891 by Dean Conant Worcester and Frank S. Bourns. Dr. Halley went to the USNM earlier this year, to examine these specimens, and found that they too had white throats like the DMNH specimen!
Halley also found evidence that the songs of D. tawitawi are unique. The mating songs of the closely related Pink-bellied Imperial Pigeon (brown-throated D. poliocephala) and White-bellied Imperial Pigeon (D. forsteni) consist of two “coos,” but recordings from Tawi-Tawi made by Desmond Allen, a British ornithologist and field guide author, consisted of 5–8 coos. Because songs are innate (genetically encoded) in pigeons and doves, this implies that these populations are reproductively isolated—more evidence that D. tawitawi was an undescribed species.
complex, as demonstrated by adult males held in the Delaware Museum of Nature and Science, Wilmington:
(A) DMNH 4501: Samar, May 1970; (B) DMNH 66314: Sibuyan, June 1973; (C) DMNH 1701: Mindanao, June
1961; (D) DMNH 14999: Tawi-Tawi, December 1971; (E) DMNH 10576: Mindoro, March 1971; (F) DMNH
66318: Marinduque, April 1972; (G) DMNH 3501: Luzon, March 1969 (Matthew R. Halley)
Amazingly, this isn’t the first time Dr. Halley has uncovered a new kind of bird. In previous years, he led a team that described a cryptic new species (Catharus arcanus) and two new subspecies (C. opertaneus tenebris, C. berlepschi nebulus) of nightingale-thrush from Panama, Ecuador and Peru, respectively, and he has also described two new subspecies of tailorbirds (genus Orthotomus) from the Philippines. The holotypes of the tailorbird subspecies are in the DelMNS collection.
D. tawitawi is the first new Ducula species to be identified in almost one hundred years—without a doubt, there’s always something extraordinary to find in the collections at the Delaware Museum of Nature and Science!
References
Halley, M. R. 2022. A new subspecies of Black-headed Tailorbird Orthotomus nigriceps (Cisticolidae) and clarification of age-related plumage sequences. Journal of Asian Ornithology 38: 129–134
Halley, M. R., Catanach, T. A., Klicka, J., and J. D. Weckstein. 2023. Integrative taxonomy reveals hidden diversity in the Catharus fuscater (Passeriformes: Turdidae) complex in Central and South America. Zoological Journal of the Linnean Society 199: 228–262.
Halley, M. R. 2025. Plumage variation in White-eared Tailorbird Orthotomus cinereiceps (Cisticolidae) with a description of a new subspecies from Mindanao, Philippines. Journal of Asian Ornithology 41: 51–57.
Halley, M. R. 2026. A new species of imperial pigeon (Columbidae: Ducula) from Tawi-Tawi, Philippines. Bulletin of the British Ornithologists’ Club 146: 295–310.
