Paul L. Errington

The Evaluation of Nesting Losses and Juvenile Mortality of the Ring-Necked Pheasant

Stoddard (1931, pp. 224-225) concluded after his first 5 years of intensive study of the bob-white quail (Colinus virginianus) in southeastern United States that 60% to 80% of the nesting attempts could normally be expected to fail. Nevertheless, few pairs were completely unsuccessful in bringing off young, as, in the event of loss or abandonment of one or of successive clutches of eggs before hatching, renesting attempts were usually made unless the season was too late or the breeding birds were in poor condition. The heavy nesting losses, therefore, served to delay rather than to prevent the final hatching of a brood by a breeding pair, with a resulting higher percentage of immature birds by fall and a lower total hatch and percentage of young birds reared. No evidence was found that the bob-white made any effort to produce a second brood in the same season if a first was successful. Erringtons (1933) data on 69 bob-white nests in Wisconsin, so far as they go, substantiated Stoddards findings. Like the bob-white, the introduced ring-necked pheasant (Phasianus colchicus torquatus) is capable of repeated renesting attempts during the breeding season if previous efforts to bring off a brood have failed. It, too, appears to be a typically one-brood-per-season bird, though the evidence on this point is not conclusive. We have a record of one pheasant brood hatched about April 30, 1933, and it may be possible that a hen hatching out a brood as early as this may still have time, ability, and inclination to bring off a second brood by mid-summer. Even early young, however, are seldom hatched before the latter part of May in Iowa pheasant range and these are commonly seen in regular company with adults as late as August, when the laying season is essentially

The Special Responsiveness of Minks to Epizootics in Muskrat Populations

The exploitation of such a valuable fur-bearer as the muskrat (Ondcatra zibethicus) by the closely associated mink(Mustela vison) is sufficiently conspicuous over the common range of the two species in North America to arouse the antipathies of muskrat trappers. Likewise, the relationships between one of the most prolific and widely distributed of rodents and its most formidable racial enemy are of interest to biologists. However much the philosophical approaches of trapper or of biologist may differ, many people in both groups impute to mink predation a very great depressive influence on muskrat populations. The life history, behavior, ecology, and population dynamics of the muskrat have been investigated on a year-around basis on Iowa marsh and stream areas since 1934. Of all the specific subjects thus investigated on the Iowa areas kept under intensive, longterm observation, one must rate mink-muskrat relationships as being by now among the most fully explored. Still, the subject is one about which it is easy to learn things that look true but are not. The Iowa investigations verify some of the major beliefs of outdoorsmen concerning mink-muskrat relationships. The mink usually is able to kill muskrats if any wild predator can, and, under a variety

Natural Restocking of Muskrat-Vacant Habitats

In late years, many of the habitats of Iowa muskrats (Ondatra z. zibethica) have been practically devoid of the animals by spring. Not only has severe winter-killing occurred during recent droughts, but some of these droughts have also concentrated and handicapped population remnants so much that they were annihilated locally by public trapping for fur. Even when environmental conditions were favorable to the muskrats, trapping was often drastic-especially when the market price for pelts reached a dollar or more, flat rate.

Food Habits of Marsh Hawks in the Glaciated Prairie Region of North-Central United States

Both authors have for some years been interested in the correlation of the food habits of the marsh hawk (Circus hudsonius (Linn.)) with the availability of prey species and have, with this objective in mind, carried on studies in different types of North-Central States environment. The need was felt especially for data of recent origin secured from areas with which one author or the other was intimately familiar. The literature, therefore, has been of limited help to us except in a general way, and we have relied primarily upon the products of our own joint or separate investigations.