What primarily governs the timing of the northward push for orioles returning from Central America?

Answer

Photoperiod changes and weather fronts.

The date of arrival in the spring is keyed to changes in the length of daylight (photoperiod) and specific weather fronts that serve as the trigger for the northward migration segment.

What primarily governs the timing of the northward push for orioles returning from Central America?
locationbirdanimalmigrationoriole