What factor means that observed ground feeding near human habitation is often heavily biased toward grains?

Answer

The sheer volume of seed they consume in proximity to human habitation.

While they consume insects found close to the ground, the large volume of seed available near human dwellings means that the observed ground feeding is frequently dominated by grains.

What factor means that observed ground feeding near human habitation is often heavily biased toward grains?
dietbirdfeedgroundHouse Sparrow