Research Training Program

Differences in microscopic characters of plumulaceous barbs has proven to be valuable in the identification of many different groups of birds. However, the function of the diagnostic nodal characters is still unknown. This investigation describes the nodal morphology of the plumulaceous barbs in the family Anatidae by comparing microscopic feather characters in two tribes: Aythyini (diving ducks) and Anatini (dabbling ducks). Thirteen species of ducks were selected according to feeding habits, habitat preferences, diving skills and number of specimens available in the collection of the NMNH. Eight species of diving ducks of the tribe Aythyini were identified for exhibiting preferences for foraging in deep waters at different depths. Three species of this group were considered as medium divers because, although they are good divers, they prefer to forage in shallow waters by tipping on the surface of the water. Five species from the tribe Anatini were selected as typical dabbling ducks for comparison. The microscopic feather characters examined in this study include: number of barbules with expanded nodes, number of expanded nodes per barbule, length of the barbule and node width. The analysis of the microscopic characters revealed that there are differences between the three groups of ducks (diver, mid-diver, and non-diver) for three of the four characters studied. Within the diving species, the depth and duration of dives was compared with each character and the results provide support for a decrease in the size and number of nodes as depth and time under water increased. More studies need to be done including other diving groups and other nodal characters, in order to understand if the simplified nodal morphology observed in this study could function to prevent entrapment of air in diving birds.

This research was supported by a grant from the Smithsonian Women Committee Research Experiences for Undergraduates program

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