Reliability of determining adults from juvenile ducks by presence or absence of notched tail feathers in various species of North American ducks

• Main Author: Siwarski, Thomas Michael
• Format: Text
• Language: unknown
• Published: LSU Digital Commons 2006
• Subjects: Aythya affinis; lesser scaup; Anas strepera; gadwall; redhead; Anas americana; tail molt; age determination; mallard; Anas platyrhynchos; northern pintail; Anas acuta; morphometric measures; Environmental Sciences
• Online Access: https://digitalcommons.lsu.edu/gradschool_theses/2905; https://doi.org/10.31390/gradschool_theses.2905; https://digitalcommons.lsu.edu/context/gradschool_theses/article/3904/viewcontent/uc.pdf

I estimated when juvenile tail molt occurs for several commonly harvested duck species, mallards (Anas platyrhynchos), northern pintails (A. acuta) (hereafter referred to as pintails), gadwalls (A. strepera), lesser scaup (Aythya affinis), and redheads (A. americana). Tests showed that aging mallards by notched tail feathers became unreliable the earliest (early September), followed closely by pintails (mid-late September), with gadwalls being the latest of the dabbling ducks to lose reliability in aging by notched tail feathers (late November). Lesser scaup and redheads retained their notched tail feathers throughout January and the completion of hunting season. Based on initial banding and band recovery data I was able to separate birds into three age classes, juvenile (59), 1.5 years old adults (11), and adults 2.5 years old or older (23), creating a total sample size of 93 birds. From this sample of known-age banded birds I recorded five morhpometric variables including weight, wing length, bill length, tarsus length, and total length to determine if body size is related to ages over 1 year. Tests revealed that the only significant difference between the age classes was in wing length. However further tests showed that differences were not apparent between the 1.5 year old and 2.5 year old or older adults.