: The coat and feather cover of birds is a good thermal insulation against cold winter and hot summer. In order to study the process of heat and mass transfer in a feather-like covering, first the permeability tensor and the thermal properties of this covering must be extracted. In this study, through the laboratory method and numerical simulation, the permeability coefficient of the bird's cover is studied. In the laboratory part, feathers of 23 birds were tested and the diameter, density, and permeability coefficient are measured in various porosities. The barbules diameter of the studied birds increases with increasing the mass and their body length. With numerically simulating the structure of bird’s feathers, the effect of cover’s permeability coefficient on fiber diameter, fiber volume fraction and Pennaceous fiber arrangement is studied. The permeability coefficient is decreased with increasing the fiber volume fraction nonlinearly. The average dimensionless permeability coefficient for the simulated angles in the 1%, 3%, 5%, and 7% fiber volume fraction is 68.09, 17.65, 8.84, and 4.46 respectively. In different fiber volume fraction, with increasing the rachis angle from 0 to 90 degrees, the average permeability coefficient decreased more than 26%. Moreover, by increasing the angle of the feather’s rachis, the variation in the angles of barb and barbule had less effect on the permeability coefficient. In order to calculate the radiation properties of the feather-like covering, a code is written based on the Monte-Carlo method and effect of the radiation properties of feather-like covering is studied according to the fiber diameter, fiber volume fraction, fiber color and fiber arrangement. In the volume fraction of the studied fibers, with increasing the fiber diameter from 5 ?m to 20 ?m, the average extinction coefficient is decreased by 75%. Also in the studied diameters, with increasing the fiber volume fraction from 1% to 7%, the average extinction coefficient increased more than 6 times. The color of the fiber is the most important influential characteristic on the ratio of the scattering coefficient versus the extinction coefficient. In the light color fibers, with increasing the fiber volume fraction from 1% to 7%, the average ratio of the scattering coefficient versus the extinction coefficient is decreased by 12%. With extraction the permeability coefficients and radiation properties for various states, the heat transfer of the feather-like covering subjected to the sunlight is possible. Covering thickness, color, diameter and fiber volume fraction are the issues that are studied on the heat transfer of feather-like covering in winter and summer conditions. The results of this study show that the heat transfer of the feather-like covering subjected to the sun and the wind is the function of various characteristics. Increasing or decreasing each of these characteristics according to the season, sunlight and wind speed will have different results in the heat transfer rate. As an example, in the calm winter conditions, although the fiber diameter increases from 5 ?m to 20 ?m leads to increase 7.4% in the heat loss at night, the heat absorption is increased 46.7% during the day. In the absence of the wind, the surface including the dark cover absorbs more heat from the sun than the light cover up to 27%; however, with increasing the wind speed growing to 5 m/s, the heat transfer difference between the dark and light cover is reduced to less than 3%. In the same weather conditions, different kinds of birds have the different covering thickness, diameter, arrangement and the volume fraction; the set of these characteristics are chosen to provide thermal comfort for the bird. Keywords: Heat transfer, Feather-like, Porous media, Radiation, Forced convection