A review of waterfowl investigations and a comparison of aerial and ground censusing of waterfowl at Minto Flats, Alaska

The Minto Flats is one of the important waterfowl concentration areas of interior Alaska. Aerial surveys and ground studies were initiated in this area in 1950 and have continued in succeeding years. This study began in September, 1955, as a research project of the Alaska Cooperative Wildlife Research Unit. The study was financed largely by Pitman-Robertson Project Alaska W-3-R. The Minto Flats is an area of about 450 square miles, located about 35 miles west of Fairbanks. The important nesting species are scaup, pintail and widgeon. The Minto Lakes area serves as an important molting and flocking area for these and other species. Climatically the Minto Flats resemble the rest of interior Alaska. Water levels in the area are highly variable and influence the vegetation and breeding. Minto Lakes, Big Lake, and the Tolovana Flats were selected for concentrated study in 1956. During the 1956 field studies, data were collected for comparison with data available from previous years. Waterfowl production in the Minto Flats area is affected principally by weather, changes in water level, and predation. Among the factors influencing censusing are the census methods, stratification, and sample size. Enumeration of waterfowl is affected by differences in the visibility of birds, population composition, environmental conditions, and the accuracy of observers in relation to the other variables and in regard to individual partiality and talent. The difference between observers, when analyzed statistically points out the need for continuity of observers with known levels of ability. Breeding bird census figures from aerial surveys from 1950 t o 1956 are not comparable due to differences in census methods. Aerial brood surveys are valuable for determining year to year production trends while ground surveys provide data on brood species composition. Together they are the best guide to waterfowl production. Nesting studies have provided some data on nesting terrain, clutch size, and nesting success. The effect of nest hunting on the breeding population and the time necessary for obtaining an adequate sample indicates that nest hunting is not an economical or accurate means of measuring yearly productive success. Aerial surveys are recognized as the most feasible way of measuring production if the accuracy of the information gathered from the air can be increased

Requirement for the Murine Zinc Finger Protein ZFR in Perigastrulation Growth and Survival

The transition from preimplantation to postimplantation development leads to the initiation of complex cellular differentiation and morphogenetic movements, a dramatic decrease in cell cycle length, and a commensurate increase in the size of the embryo. Accompanying these changes is the need for the transfer of nutrients from the mother to the embryo and the elaboration of sophisticated genetic networks that monitor genomic integrity and the homeostatic control of cellular growth, differentiation, and programmed cell death. To determine the function of the murine zinc finger protein ZFR in these events, we generated mice carrying a null mutation in the gene encoding it. Homozygous mutant embryos form normal-appearing blastocysts that implant and initiate the process of gastrulation. Mutant embryos form mesoderm but they are delayed in their development and fail to form normal anterior embryonic structures. Loss of ZFR function leads to both an increase in programmed cell death and a decrease in mitotic index, especially in the region of the distal tip of the embryonic ectoderm. Mutant embryos also have an apparent reduction in apical vacuoles in the columnar visceral endoderm cells in the extraembryonic region. Together, these cellular phenotypes lead to a dramatic development delay and embryonic death by 8 to 9 days of gestation, which are independent of p53 function