Open AccessSex Ratios and Age Ratios in North American Ducks
Author(s) -
Frank C. Bellrose,
Thomas G. Scott,
Arthur S. Hawkins,
Jessop B. Low
Publication year - 1961
Publication title -
illinois natural history survey bulletin/bulletin - illinois natural history survey
Language(s) - English
Resource type - Journals
eISSN - 2644-0687
pISSN - 0073-4918
DOI - 10.21900/j.inhs.v27.175
Subject(s) - waterfowl , juvenile , sex ratio , biology , productivity , population , ecology , sexual maturity , zoology , demography , fishery , habitat , macroeconomics , sociology , economics
The sex classes and age classes of various species of ducks constitute measurable elements of the populations. The present study deals primarily with sex ratios and age ratios and the ways in which they relate to population productivity. The present study is an evaluation of sex and age ratios in North American duck populations and the ways in which, in waterfowl management, these ratios can be used to measure productivity. Drakes occurred in relatively greater numbers among diving ducks than among dabblers; however, examination of the available knowledge on the reproductive biology characterizing these two subfamilies revealed nothing which suggests that extra drakes may be more important to the maintenance of populations of diving ducks than of dabblers. Juveniles were found to be more vulnerable to hunting than adults; the vulnerability differential varied with place, time of hunting season, vear, and species. Age ratios obtained from bagged ducks and corrected for the greater vulnerability of juveniles offered the best means of determining the adult-juvenile composition of duck populations.