In year’s past Yellow Warblers were exceedingly uncommon in Texas in the winter season. There would always be that odd one or two in the extreme lower Rio Grande Valley, but by in large they were absent until returning in the spring. Of course there are those warbler species that winter here at the northern fringe of their wintering range (Black-and-white, Black-throated Green, Wilson’s, Ovenbird, Northern Waterthrush), but Yellow, for the most past, has not been among this group.

In the past several years this has changed. Now Yellow is being seen regularly in winter as far north as the Coastal Bend (see Ebird map). This year there have been several along the central coast, including one in Port Aransas at the Turnbull Birding Center and four at Hans Suter Park in Corpus Christi. There have also been several Rose-breasted Grosbeaks, with one seen as far north as Galveston. So what gives?

As most CBC participants are aware, there are good years and there are bad years. There are years when there are volumes of lingering migrants, and there are years when you couldn’t buy one. But when we look across the vagaries of these annual fluctuations, it does appear as though there are increasing numbers of neotropical migrants that are short-stopping their flights to the tropics to spend the winter season along our coast.

The difficulty with assessing the concepts of global warming as applied (not theorized) is in finding tangible evidence of its impacts. Sea level rise in Texas? No problem. Melting ice shelves and glaciers? Got ’em. Rising mortality in coniferous (boreal) forests? No doubt. But what about these seemingly insignificant scraps of evidence such as lingering neotropical migrants or tropical species (Couch’s Kingbird, Green Jay, Greater Kiskadee, Clay-colored Thrush) pushing north? Aren’t these just as important in piecing together the global effects of temperature changes?

Texas is on the frontier of this work. By being positioned at the doorstep of the tropics, slight changes in northern ranges in bird species are felt here first. This is precisely why it is critical to collect as much information on these wintering birds as possible, including being sure that the data related to these sightings are entered into a repository such as eBird. Yes, it is great fun to find a rarity out of season (such as the recent Swainson’s Thrush). But this find may also provide evidence of a much more significant change afoot, one that will ultimately impact us all, feathered or not.

Of course you can contribute to piecing this puzzle together. Enter your sightings, not matter how brief or (to you) insignificant into Texas eBird. The combined efforts of thousands of birders are critical to documenting these changes at the landscape scale. Spend the time necessary to correctly document and identify these lingerers (isn’t it amazing how many species one can turn an Orange-crowned Warbler into?). Finally, follow these lingering neotrops throughout the season. Some are late fall migrants, but many are true winter residents. The trends in those that actually remain here for the entire winter could be a critical study.