Tuesday, November 13, 2007

Green-breasted Mango captured!

Green-breasted Mango, courtesy of Bill Hilton and Hilton Pond.

The Green-breasted Mango, Anthracothorax prevostii, is a spectacular (are any hummingbirds not?) species of Mexico and Central America. In their normal haunts, mangos can be common and don't cause much of a stir. North of the U.S. border, it's a different story.

The first United States Green-breasted Mango was found in south Texas in 1988. Since then, records have steadily picked up in the Rio Grande Valley region. To date, there have been but three records elsewhere in the U.S.; North Carolina in 2000, Georgia just this past October, and the subject of this post - a bird that turned up in Beloit, Wisconsin back in September. All have been juvenile males (the bird pictured above is an adult).

The birding blogosphere has been alive with buzz about the recent capture of the Beloit bird. As it tarried on, frequenting the same feeder where it was found, Wisconsin's famously frosty winter began to set in, as it does every year. This prompted some of the local birders to understandably worry about the fate of the mango. After all, tropical hummingbirds are not well-equipped to withstand the ravages of cold, snow, ice, and sub-freezing temperatures.

So, a few days back well-intentioned mango fans captured the bird, and have made a home for it at the Brookfield Zoo near Chicago. The questionable legality of this bit of do-gooderism aside, a few other issues pop to mind. First, should we really meddle with wild birds like this? This Green-breasted Mango reached Wisconsin on its own power, and although it did seem increasingly unlikely that it would flee the onset of winter successfully, one never knows. We get Rufous Hummingbirds annually now in Ohio - as do many other northern states - and they frequently linger into very cold weather. Most then disappear, and in some cases have reappeared again the following year, demonstrating that they were able to bail out on weather that would eventually do them in, and manage to return to more hospitable climes. Strong fliers like hummingbirds can cover great distances quite speedily if need be. Good ole Ruby-throated Hummingbirds migrate 500 miles across open waters of the Gulf of Mexico, and probably do so in about 24 hours. Mangos can likely move along at the same clip, which means the Wisconsin bird could be a much warmer bundle of feathers quite soon should it have decided to speed due south, which it may well have eventually.

What this mango is doing is part and parcel of evolution, a beautiful process that humans would do well to leave alone. Many species of birds, and flighted insects, send pioneering scouts far beyond their normal range. No, it's not part of a conscious plan of attack by the Green-breasted Mango Central Committee; rather it is just the constant underlying energetic need of a species to expand and conquer. We humans do it, too, most relentlessly of all. With birds, it is often the young males that go far beyond the pale to prospect, searching out possible new empires to colonize. One might think of a species like Green-breasted Mango as an inert bag of popcorn (stay with me). Most of the year, the kernels in the bag just sit there, happily remaining in their range (the bag). However, once a year - fall, typically - the microwave activates and begins jostling the kernels. As they pop, some are flung very far from the core population. Nothing will come of most of these wayward kernels, especially the ones that end up far distances from home, like the Beloit mango.

Some of the explorers eventually stick, though - witness mangos going from a first U.S. record in 1988 to becoming regular in south Texas now. Over long periods of time, this is how bird populations expand. Sure, the Wisconsin mango isn't going to start a new breeding colony amongst the cheeseheads, but it is still part of mango evolutionary expansion. We should leave it alone.

Hummingbirds, and insects like butterflies and dragonflies, are environmental change hyper-responders. Because of their extreme mobility and ability to benefit from slight temperature changes that cause greater food sources such as nectar and prey insects for longer periods, some species in these groups have become conspicuous northward invaders in recent times. Witness the now common phenomenon of western/southern hummers into the Midwest. Ohio's first non-Ruby-throated Hummingbird was a Rufous Hummingbird in 1985; now we've had dozens of records and three other species have appeared since. As temperatures gradually warm, we will see more and more northward hummers.

What if we were to capture all of these extralimital hummingbirds because of foolish and unfounded fears about their well-being? It would be like erecting a Hoover Dam to staunch nature's grand scheme, the continuous ebb and flow of species trying to expand their populations and evolve. Over the eons, in huge time spans that most of us humans don't do well grasping, such wayward vagrancy in fits and spurts led to the evolution of the fantastic phenomenon of waves of migrant warblers, vireos, flycatchers, and other neotropical wanderers. I don't mean to criticize any indivuals for the Wisconsin mango fiasco; after all it is all too common for people to think we know what is best for nature, and to manipulate it. The reasons for the mango capture are well-intentioned; unfortunately the basic understanding of nature and biology that drove this action are lacking.

For a good solution to the Beloit mango, go here.

For an interesting read from the Milwaukee Journal Sentinel, go here.

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