The birds strongly preferred the conventionally grown, non-organic seeds. When the feeder positions were switched, the birds quickly switched as well so as to continue to eat the conventional seeds.
The scientists suspect that the preference was due to the higher protein content in the non-organic seeds. On average, the conventional seeds had 10% more protein, a significant difference to a small bird trying to maintain energy levels.
Lab tests of captive canaries confirmed the avian preference for non-organic feed.
As McKenzie explains:
Conventionally-grown crops tend to contain significantly higher levels of protein than those grown organically due to the application of inorganic nitrogen fertilizers in conventional farming systems. This makes our findings potentially applicable across many food types and suggests the issues surrounding organic food are not as cut and dried as some might think.