Hummingbird Science, Part I

Last time we shared the counting methods of a true hummingbird expert, Sheri Williamson. Ms. Williamson is the author of the Peterson A Field Guide to Hummingbirds of North America which, at the risk of her accusing us of “absolutely gushing” — something we leave to artesian wells — is a fine book; full of useful information. Ms. Williamson has forgotten more about hummingbirds than we will ever know. She has blogs and a website which you can find here, here and here.

Still, we thought her post a bit haughty; written with a certainty and hubris scientists are well advised to avoid. In addition to calling Dan True’s book on hummingbirds “full of half-baked ideas, misinterpretations of other people’s work, and out-of-date information. . . .” she accuses us of misleading you into thinking that Ruby-throated Hummingbirds migrate over the Gulf of Mexico rather than taking the longer shoreline route. More about that in a minute.

First though, a word about science. Science is the best, most successful method of describing and explaining reality yet invented. But it is slow. It has to be. Hypotheses must be developed, data painstakingly accumulated, tested and peer reviewed. Even after a theory explaining all the known data is erected, wise scientists know the entire edifice can come crumbling down on their heads if a new pertinent, reliable piece of data is discovered which contradicts all that earlier work. We have a scientist friend who is delighted if he is right half the time.

More important, ignorance engulfs us. We must stand stupefied before all we do not know. Why was there a “Big Bang?” What does it mean to say that a black hole is a singularity? How do electrons act at a distance? How many dimensions exist? Are Boltzman Brains really possible? What is consciousness? Why is so much of the world explainable by mathematics? What cures the common cold? How can we stop cancer cells before they kill their hosts? How did Aspen trees learn to clone themselves? Why do some thunderstorms become super cells? How do birds navigate? What routes do Ruby-throated Hummingbirds follow on their migrations? How many are eating at your feeder?

Here is a scientist on the point:

As a human being, one has been endowed with just enough intelligence to be able to see how clearly, how utterly inadequate that intelligence is when confronted with what exists.
Albert Einstein.

But to get back to Ms. Williamson’s complaint about our post. Here is what she said:

One additional nitpick about the TFFBBB entry: It assumes that Ruby-throated Hummingbirds migrate south across the Gulf of Mexico when the evidence strongly suggests that the majority take an overland route around the Gulf in fall migration.

First, we did assume that large numbers of Ruby-throats migrate south across the Gulf of Mexico. And, while we are not — and never claimed to be — scientists, we don’t just make stuff up. Our statement that Ruby-throats fly directly over the Gulf of Mexico in autumn had two scientific sources.

The first, which we utilize frequently, is Cornell University’s Birds of North America. (BNA) (Available online, subscription required) According to one ornithologist: (Sheri Williamson, actually)

The most valuable published resource on the biology and natural history of North America’s hummingbirds is the Birds of North America series. . . .

Here is what BNA has to say about Ruby-throat migration:

Despite their tiny size, many of these birds fly nonstop across the Gulf of Mexico during fall and spring migration, a round-trip of more than 1,600 km. To accomplish this, individuals often double their body mass by fattening on nectar and insects prior to departure. (Emphasis added)

There is one problem with BNA. It is not updated frequently. For instance, the article on Ruby-throated Hummingbirds was written in 1996. So we checked one other, newer source: The 2001 Peterson A Field Guide to Hummingbirds of North America by Sheri Williamson. (That name sounds familiar, where have we heard it before?) In that book, at page 188, we read:

To reach their eastern nesting grounds each spring, many individuals take a direct but hazardous route across the Gulf of Mexico, flying non-stop over [sic] more than 500 miles of open water.

But, you say, that is the northbound trip. Could the southbound trip be different? Possibly. And, Ms. Williamson may have newer data and we hope she will share it with our readers and hers.

But the range map on page 192 of Ms. Williamson’s book flatly states:

Both trans-Gulf and overland migration routes used in spring and fall. (Emphasis added)

To be fair, both BNA and Ms. Williamson hedge their bets. BNA says:

Many fly across Gulf of Mexico, but many also follow coastal route. Routes may differ for north- and southbound birds. . .In general, however, migratory routes of this species remain poorly documented, and some proportion of the population may follow a coastal route south during the fall.

Ms. Williamson, on page 29 of her book, states:

Ruby-throated hummingbirds wintering in Central America take the most direct route available in spring migration, up the Yucatan Peninsula and across the Gulf of Mexico. This route would be dangerous in reverse, with a significant chance of missing the peninsula which may be one reason many thousands of southbound Ruby-throats follow the Gulf Coast through Louisiana and Texas.

To us, that smacks of anthropomorphism. The Yucatan Peninsula is a pretty big place and just because a flying human might miss it, doesn’t mean that Ruby-throated Hummingbirds, whose ancestors have been finding it for hundreds of thousands of years, will. Besides, even if they somehow missed it, the odds are good that they would make land-fall in Central America or in South America; another, even bigger place. Only an east-bound bird, leaving from Florida, could miss land. That would only be possible if the prevailing winds were blowing east, but we know the Trade Winds over the Atlantic blow toward the Gulf so would not be likely to blow birds out to sea.

But that isn’t science. To know for sure we need a professional meteorologist to tell us about the prevailing wind and weather patterns of the Gulf of Mexico. Then we might know if there was any autumnal danger for Ruby-throated Hummingbirds “missing” the Yucatan Peninsula.

We could ask Dan True.

Tags: Gulf of Mexico, Hummingbird MIgration, Hummingbirds, migration, Ruby-throated Hummingbirds