Laura Erickson's For the Birds

The Brownsville Dump’s biggest claim to fame, at least in the birding world, was being the only place in the United States where this species could be reliably found, at least from the 1970s into the 1990s. This is the species Steve Martin’s character searched for at the dump in the movie The Big Year. Russ and I had tried for this species back in 1978, right after the Brownsville Dump location was moved—we went to the wrong one and were skunked. I saw my lifer at the dump on 10 February 1991. The crows were already dwindling by then, and after they completely disappeared, it was many years until one was sighted again in November 2017, when lots of birders in the Rio Grande Valley got to enjoy sightings once again. It will be interesting to see if they stick around longer this time.

According to Neotropical Birds:

Formerly treated as conspecific with Sinaloa Crow (Corvus sinaloae) under the name Mexican Crow, Tamaulipas Crow is fundamentally endemic to northeast Mexico, although it is regularly recorded in the southernmost corner of the United States, in southeast Texas, principally during the nonbreeding season. This small, slender crow’s plumage is entirely black, but is glossed purple, blue, and green. Morphologically it differs from Sinaloa Crow solely in having a slightly shorter tail. However, its lower-pitched vocalizations and genetic distance appear to confirm the split from the Sinaloa Crow. Tamaulipas Crow is generally found below 300 m, where it inhabits scrubby farmland and open woodland, as well as habitation, where it regularly attends rubbish dumps.