Date: 1/30/18 5:14 pm From: John Fussell <jofuss...> Subject: Do feeders keep hummingbirds from migrating south in the fall?
Recently on this listserv there was a bit of discussion about whether feeders keep hummingbirds from migrating south in the fall. This discussion was prompted by reports, including mine, of mortality/apparent mortality of hummingbirds in eastern North Carolina during the persistent cold in early January.
I doubt that feeders keep hummers from going south in fall, at least to any significant extent.
Every winter, especially in early winter, birders find many individuals of many species of landbirds that did not go south to "where they should be". These are birds of varying sensitivities to cold or to lack of food due to cold. Most are insectivorous; they do not use feeders. They include warblers and many other species. Many of these birds will not survive the winter, especially if there are periods of severe cold and/or icy weather. Perhaps the most unfortunate of these birds that did not "go far enough south" are those that really screw up, and actually go northward in the fall, ending up in places like Nova Scotia and Newfoundland, where they are certainly doomed. A large percentage, probably a majority, of these "lost" birds are immatures. (I wonder if immature males predominate--am thinking of the human analogy!)
I looked back through old Chat magazines recently to check on my memory. Hummingbirds, presumably almost all Ruby-throateds, were occasionally spotted in early winter well before there were any feeders being maintained in winter--in fact, to the best my knowledge, back when very few persons maintained hummingbird feeders at any season. For instance, in my county of Carteret there were four reports (at four different sites) of hummers in early to mid-winter (early December to mid-January) in 1979-1980. Again, these birds were not here because of any feeders. Some of you old-timers may remember that particular winter. It was very mild in December and through most of January (I remember the flowers where I was staying in late January), but then we went into a deep freeze in February, topped off by a snowstorm at the beginning of March. During that winter I think that many hummers could have survived without a feeder through most of January, but would have been doomed later on.
However, I do think it is likely that we are sustaining a wintering population of hummingbirds that is occurring somewhat farther north than where it would survive without feeders. I am not saying that we are keeping individual birds from migrating south, but that perhaps by keeping birds with a genetic tendency to not migrate farther south in winter from perishing, we are allowing such birds to survive and reproduce, thus contributing to this more northerly wintering population. In this regard, I think back to the first wintering birds at feeders in my area (I think it was in the late 1980's/early 1990's). We were arguing a lot about what species they were, in part because we had heard so much from Gulf Coast birders about how our birds could NOT be Ruby-throateds, but also because those first wintering birds at feeders were almost exclusively immature birds--we did not see any adult males which would have helped us identify them more confidently.
If we are maintaining a more northerly wintering population, is that good, bad, or neutral? Might there be an intense winter storm some year that will eventually wipe out most of this wintering population (such as the "blizzard" of December 1989--I can't believe a single hummer could have survived that weather here). Or will such events become increasingly less likely in a warming world (although some research suggests that a warming Arctic leads to wilder kinks in the jet stream, resulting in some invasions of very cold air into the eastern Unitied States, like the recent cold). Anyway, the cold in early January was statistically a very rare event, especially in terms of its persistence. As I've said earlier on this listserv (I think I have anyway), I have had wintering hummers in my yard since 2002-2003. I think the only hummers that have died here during this period other than the ones this year were two (of eight birds) in January 2003. The conditions then were actually more severe than this winter, but they did not last as long.
Another comment I have is if one thinks that hummingbird feeders keep hummers from going south, shouldn't we also be concerned about plants that flower in winter, most of which are exotic planted (and invasive) species like sasanqua and elaeagnus, although there are native ones like coral honeysuckle. I have seen hummers in winter that were associated with thick growths of elaeagnus that were nowhere close to any feeders. And how about those relatively cozy micro-climate situations, many of which are man-made, although there are some natural ones too. I remember one mid-December day watching a Ruby-throated that was going after swarms of tiny flying insects over a relatively warm south-facing slope (on a dredge island). And there was a coral honeysuckle plant with numerous flowers at that same site.
Something I do feel very strongly about: If someone has been feeding hummingbirds in winter such that the birds are really tied to that particular yard, I think they have an obligation to keep those feeders maintained throughout the winter, but especially in really cold, severe weather. When conditions get really bad, and the birds are really stressed, they will not have the luxury of making a long flight. I feel that this is especially the case for people like me, who do not live close to any other feeders.
And, a final comment: I remember when I was in college being told (by my major professor) that beginning about 1950 feeders had kept Baltimore Orioles from migrating south to Central America. Do we think that is really true? Or is more likely that orioles that did not migrate south to "where they should have gone" found feeders, which enhanced their survival. I think the latter is more likely.
Susan Campbell and Ann Maddock may want to make some comments about my thoughts, especially in regard to the degree that Ruby-throateds might survive in witner without feeders. I do think that for my area--Carteret County--hummers would not be able to survive throughout an average winter, although they might (and obviously have) survive well into a typical December, and into January of some years.