Body weight (mass) and plumage reflectance of birds are related to their ability to conserve and/or release heat and maintain thermal equilibrium. Although 55% of the light reflectance of bird feathers is in the NIR spectral range, this has been poorly studied, and research has focused mainly on UV and VIS wavelengths (300 to 700 nm). In addition, environmental factors, plumage structural properties, bird behavior and physiology make the absorbance/reflectance and thermal load relationship difficult to explain. In this work we used a spring scale and a spectrometer AvaSpec ULS2048L to analyze the relationships between avian weight and reflectance (between 300 to 1000 nm) of 13 body patches of 53 lowland bird species from Santander, Colombia. The results of a Principal Component Analysis (PCA) showed that reflectance values from the VIS and NIR regions can distinguish the lighter from the heavier birds. Moreover, multiple linear regression models showed that heavy birds had significantly higher NIR reflectance values (p-values < 0.05) compared to lighter birds. The patches most strongly related to the NIR range were the upper and lower back regions, showing that the birds have a high reflectance in the body regions that are exposed directly to the sunlight. This suggests that the high reflectance of feathers in the NIR range may be a bird strategy to dissipate heat, avoid overheating and maintain an optimal body temperature.