Líffræðifélag Íslands
Líffræðiráðstefnan 2015
Erindi/veggspjald / Talk/poster V29
Gunnar Thor Hallgrimsson (1,2), Halfdan H. Helgason (2,3), Elinborg S. Palsdottir (2,3), Snæbjörn Palsson (1)
1. University of Iceland, Department of Life and Environmental Sciences, 2. Southwest Iceland Nature Research Institute, 3. Norwegian Polar Institute
Kynnir / Presenter: Gunnar Þór Hallgrímsson
Tengiliður / Corresponding author: Gunnar Þór Hallgrímsson (gunnih@hi.is)
Gulls are monomorphic in plumage characteristics but show a sexual size dimorphism where males are larger than females. In this study we use Discriminant Function Analyses (DFA) and Generalized Linear Model (GLM) to provide sexing criterion based on morphometrics for adult and fledgling Lesser Black-backed Gulls of the subspecies graellsii. Males were significantly larger than females in all variables measured and this was the case for both age classes. The best sexing model for adults included skull length, bill depth and tarsus length and classified correctly 99.1-99.5% of the sampled individuals. Posterior sexing probability of 95% only excluded 5.4% of the adult birds from the sample. The best sexing model for fledglings included skull length and tarsus length and classified correctly 89.4-93.6% of the sampled individuals. Posterior sexing probability of 80% excluded 31.9% of the fledglings from the sample showing that relatively few birds could be sexed with high accuracy in contrast to adults. DFA and GLM showed same or similar accuracies as sexing criterion.