NATIONWIDE ESTIMATES OF BLACKBIRDS AND STARLINGS

An estimated 538 million blackbirds and Starlings are found in the United States, based on the national cooperative blackbird/Starling winter roost survey conducted by the U.S. Fish and Wildlife Service during the 1974-75 winter period of December 20-February 15. Ap- proximately 74% or 398 million of these blackbirds and Starlings occurred in the Eastern States, including the tier from Minnesota to Louisiana; 26% or 139 million birds were in the West. The national roosting population in 1974-75 was composed of 11 species (Table 1) in the following approximate proportions: 38% Red-winged Blackbirds; 22% Common Grackles; 20% Starlings; 18% Brown-headed Cowbirds; 2% Brewer’s Blackbirds; and less than 1% six species combined (Rusty Blackbirds, Boat-tailed Grackles, Great-tailed Grackles, Tri-colored Black- birds, Yellow-headed Blackbirds, and Bronzed Cowbirds). (Some 2 million robins also were reported in the 1974-75 survey, though not solicited and therefore not tabulated, from 20 of the blackbird roosts in the Southeast.) The 1974-75 species proportions are similar to those found in the last nationwide winter survey (1969-70). In the 1963-64 national winter survey, Redwings made up 33% and Common Grackles 31% of the total population.

Effective Thermal Conductivity Estimates Of Particulate Mixtures

Several theories have been advanced to estimate effective thermal conductivities of particulate mixtures, but most theories have focused on the dilute case. A method is proposed to estimate the effective thermal conductivity coefficient of mixtures of arbitrary concentration. Earlier the authors developed a theory to determine the expected contact area between different species. This theory is employed to determine the Kapitza resistance of the heterogeneous mixture and forms part of an overall theory to estimate the effective thermal conductivity. Results are compared with other theoretical estimates and with experiments.