Abstract
Subsistence harvest studies use number-to-mass conversion factors (CFn-m) to transform numbers of animals harvested into food production (CFn-m = body mass × recovery rate; where recovery rate is the percentage of the body mass represented by the processed carcass). Also, if egg harvest was reported as volume (e.g., a bucket), volume-to-number conversion factors (CFv-n) are needed to calculate the number of eggs taken. Conversion factors (CF) for subsistence harvest of birds and eggs have been based on unclear assumptions. We calculated a mean recovery rate (65%) by weighing and processing wild birds, compiled data on bird and egg mass, developed an egg CFv-n equation, and presented CF for 88 bird species, 13 subspecies or populations, and 25 species categories likely to be harvested in Alaska. We also made recommendations on how to apply and adjust CF according to study objectives. We recommend that subsistence harvest studies (1) collect egg harvest data as egg numbers (not volume); (2) clearly explain considerations and assumptions used in CF; (3) report recovery rates and mass of birds and eggs; and (4) cite original sources when referring to CF from previous studies. Attention to these points of method will improve the accuracy of food production estimates and the validity of food production comparisons across time and geographic areas.
Highlights
Number-to-Mass Conversion Factors for Birds and EggsStudies of subsistence uses of wild resources report harvest as the number of animals taken and as the amount of food produced
The following ethnographic information was used to identify bird parts that should be included as edible mass when calculating the recovery rate
Key respondents reported that Alaska subsistence users consumed wild birds as bone-in, skin-on preparations, usually as a roast or soup
Summary
Studies of subsistence uses of wild resources report harvest as the number of animals taken and as the amount of food produced (edible mass). Food production data are used to depict the relative importance of resources (e.g., moose, salmon, geese) and their role in subsistence economies (Brown and Burch, 1992), to assess exposure to contaminants derived from wild foods (Usher, 2000), and to estimate the monetary (replacement) value of harvest. Food production estimates do not account for the nutritional and cultural importance of different resources White (1953) and poultry carcass yield (Watt and Merrill, 1963), including meat, edible organs, half of the bone mass, and two-thirds of the mass of blood and feathers JBNQNHRC (1982) Poultry carcass yield, White (1953); JBNQNHRC (1982); Georgette and Loon (1993) Poultry carcass yield Researcher estimate Researcher estimate Poultry carcass yield Not explained Wolfe (1981); Braund & Associates (1993); CSIS (2016a) Wolfe (1981); CSIS (2016a) Not explained
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