Why are Bullfinches often less able to switch to common garden seeds compared to generalist species?

Answer

They are highly sensitive to changes in the availability of preferred woody food sources

Due to their powerful bill usage for expertly extracting seeds and buds, Bullfinches are highly sensitive to changes in the availability of preferred woody food sources, making them less adaptable generalists.

Why are Bullfinches often less able to switch to common garden seeds compared to generalist species?
raritybirdornithologywildlifeBullfinch