This paper describes the effects of weak collisions on the linear kinetic theory of electrostatic density drift instabilities. The model assumes a weak, uniform density gradient, a uniform magnetic field and the BGK collision operator with a modification of the local approximation to derive a dispersion equation valid at all frequencies and wave numbers. The properties of the universal and collisional density drift instabilities at maximum growth rates are presented in detail. Their thresholds in an ionospheric model, which includes ion-neutral, electron-neutral, and electron-ion collisions, are in an ionospheric model, which includes ion-neutral, electron-neutral, and electron-ion collisions, are discussed and compared with the threshold of the lower hybrid density drift instability. In particular, the ionospheric conditions (plasma density ≲106 cm altitute >250 km) and maximum scale lengths necessary to excite the universal at wavelengths of the order of the ion gyroradius are presented. We conclude that the k-5 short wavelength density power spectra observed above 280 km in the PLUMEX experiment are due to the effects of the universal density drift instability.