Common Yellowthroat is one of the most widespread warblers in the country, and unlike most warblers, is a denizen of marshes, grasslands, and wet meadows. It breeds in every one of the lower 48 states and winters across the southern states and well into Mexico and Central America.
In winter it can be found along the southern margins of the United States, but many more occur in Mexico and Central America. In April and May, this attractive warbler surges northward en masse, occurring in grasslands and marshes countrywide.
Like many species, it has an earlier migration along the Pacific Coast than in the East. Watch how the migration jumps up to fill in the coast of Oregon and Washington in mid-April, while the species is just starting to occur at more southerly latitudes in the East. With weather moving over the Pacific Ocean, the air is comparatively warmer and the climate of coastal Pacific areas is always comparatively more temperate than inland areas at the same latitudes. Many birds take advantage of this and have adjusted their migration accordingly. This is a common pattern of earlier Pacific coast arrival in these STEM maps and just one of the many fascinating migratory patterns that become obvious in these types of visualizations.