Morphometric Variation and Randomization Testing Among Museum Skins of Hornbills (Family Bucerotidae) From Borneo

Hairunizam, Amiruddin (2019) Morphometric Variation and Randomization Testing Among Museum Skins of Hornbills (Family Bucerotidae) From Borneo. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Hornbills are well-known for their diverse morphology and unique nesting behaviour. Their contribution towards forest regeneration and ethnobiological value, especially in Borneo make this group of a bird remarkable wildlife to be studied. Hornbills classifications are well established, but most of the classification only focus on their genetic relationships with a limited number of species. Up until today, no study has been conducted on classification, and intraspecific variations involved Bornean hornbills using morphometric approach. In this study, 210 of museum skin specimens were measured from eight species of Bornean hornbills. Multivariate analyses using eight morphological characters which included bill depth (BD), bill width (BW), tarsus (TR), bill length (BL), head bill length (HB), tail (TA), wing length (WL) and total length (TL) as predictor to classify eight species of Bornean hornbills according to their major clades (Berenicornis, Rhinoplax, Anorrhinus and Aceros). Wing length (WL) was the most distinctive character to discriminate between the eight species of Bornean hornbills according to their major clades with a cross-validated accuracy rate of 82.9%. Overlapping in grouping Berenicornis, Anorrhinus and Aceros showed this group are related to each other and can be classified as medium size hornbill. Rhinoplax group formed a distinct group from the other three major groups showed that this group possess the largest WL thus can be classified as large size hornbill. The difference in WL size also showed that the hornbill with large WL tend to forage at upper canopy level while small WL tends to forage at lower canopy level. Discriminant analysis on three major groups excluding large hornbill, Rhinoplax showed more characters need to increase classification resolution in Bornean hornbills. Tail (TA) is proven useful to distinguish Berenicornis from Anorrhinus and Aceros, which previously cannot be differentiated and wrongly classified iv into Rhinoplax and Anorrhinus. Meanwhile, wing length (WL) and bill depth (BD) have proven useful to group Rhinoceros hornbill and Bushy crested hornbill according to its locality (Sarawak and Kalimantan) using randomization test. There was no significant different (p<0.05) between specimens from Sarawak and Kalimantan on its WL or BD based on randomization test using 5000 and 7000 iterations. It is advisable to use 5000 iterations when the samples size between both groups are much different, while 7000 iterations when dealings with the difference sample size for both groups are small. Four discriminant models were produced which can contribute to specimens identification of Rhinoceros hornbill and Bushy crested hornbill. Studies related to museum specimens are prone to a missing value that must be treated wisely before considering involving the data into multivariate analysis. The study is giving insight into the importance and contribution on morphometric to reconstruct recent classification of Bornean hornbill.

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