How do buffs on birds work during events?

During events, certain birds receive specific buffs that make them much more effective for the duration of the specific event.

In order to see which birds are buffed, look to the top right of the Event Island's screen. 

Customarily, on the top row, you will see the special Event Birds along with their corresponding buffs.

On the second row, you will usually see the previous event's special birds along with their corresponding buffs. Please note that if a 5-star version of a 4-star bird or a Master 5-star version of a 5-star bird has appeared as an event reward, the buff pertains to these boosted versions of the birds. 

Finally, on the bottom row, you will see an attribute-specific buff. All birds that share the selected attribute, will receive the corresponding buff for the duration of the event.