Tyrannus savana

Copied from the Mass Avian Records Committee:
Fork-tailed Flycatcher is a widespread species of the Neotropics. Its four poorly-differentiated subspecies break down as follows: T. s. monachus is resident from Veracruz to Colombia; T. s. sanctaemartae is resident in a small area of Venezuela and Colombia; and T. s. circumdatus is resident in lower Amazonian Brazil. Remarkably it is T. s. savana, the most southerly subspecies which breeds from Brazil south to central Argentina and Chile, that occurs as a vagrant in the United States and Canada. This species occurs annually in the US and Canada, with most records in the Northeastern US, eastern Canada, and the Gulf Coast; more anomalous records as scattered as far north as Nunavut and as far west as California.