I will give one example: Hummingbirds use many alien species, in urban, rural, and natural areas. In Southern California (SC), for example, I have observed their use of the South American tree-tobacco, Nicotiana glauca (NG). This plant is fairly common in disturbed habitats such as farmlands and "channelized" rivers, streams, dry washes, and drainages where much of the indigenous riparian habitat has been extirpated. Under the best circumstances there are few indigenous species that provide nectar in SC riparian habitats to begin with, and fewer still that do so almost all year.
At least some ecosystem restoration (ER) projects have provided for the extirpation of NG, and control efforts have been common in management, particularly of wild areas. I use the past-tense because I have not made too many observations in recent years. 1. Do public agencies that oversee ER and manage public lands currently control NG? 2. Are there any known adverse effects of NG nectar on hummingbirds? 3. Is there any evidence that NG plays any significant role in hummingbird survival, reproduction, range extension, etc., and are any of these roles critical, as, for example, in providing otherwise deficient habitat along migration corridors, or, for that matter, effective creation of such corridors? 4. Have there been any studies, for example, hummingbird activity before and after extirpation of NG, and/or after recovery of riparian vegetation and subsequent reduction in NG populations and/or distributions? Finally, does anyone have any specific information on other examples of indigenous/alien species interactions? I am grateful for your reply. WT
