A Device for Determining Duck Brood Hatching Dates

Abstract

A circular calculator is described for determining duck brood hatching dates. The inexpensive device, which was found to be accurate and time saving, is easy to operate and construct. Biologists working with large volumes of brood data have found that special devices expedite back-dating for constructing hatching curves. Schroeder (1957) developed a series of calculators for dealing with large numbers of duck broods. Kabat et al. (1950) described a modified slide rule used for back-dating natural events in game animals. Another modified slide rule was used by Reeves (1952) for back-dating quail broods. With the exception of Schroeder's (1957) device, the aids to back-dating broods involve modifying a standard slide rule. Unfortunately, to do this accurately is difficult, and the cost of a slide rule to be modified is considerable. Schroeder's device for duck brood data consists of a set of circular calculators; one is required for each species of duck. The device described here is a single c lculator developed for determining hatching dates of duck broods in conjunction with Gollop and Marshall's (1954) field guide to aging. The hatching dates of other species, of course, can be determined where aging criteria are available. 195 also. There was no animal material in any of the stomachs. My data suggest that leading sources of food for wood ducks in the Southeast are water oak, pin oak, baldcypress, sweetgum, water hickory, ash (Fraximus sp.), green hawthorn (Crataegus viridis), and American hornbeam (Carpinus caroliniana). Where wood ducks are important, I recommend that these trees be left when timber stand improvement is being conducted on areas managed for both timber and wildlife.