Friday, February 15, 2013

No, birds do not give birth to chicks


Last time I talked about the oldest known wild bird, a Laysan Albatross nicknamed “Wisdom” who is still, at 62 years of age, producing and successfully raising young. Since her chick from this year hatched on February 3, a lot of news reports have covered the story. I’ve read the news releases put out by the US Geological Survey and know they presented accurate information, but some of the media got two important elements wrong.

First, Wisdom is definitely not the oldest bird in the world—some captive parrots live into their 80s—and she’s probably not even the oldest wild bird. What she is is the oldest wild bird that we know about. The vast majority of birds, including the vast majority of albatrosses, are never banded, so we have no means of tracking their age. Most banded birds are never retrapped—the way we get data on their ages usually comes from finding a dead bird with a leg band and finding out when it was first banded. Of the birds that are banded, only a tiny fraction are caught again, and only in a few careful studies, such as Ryan Brady’s tracking of the oldest known Northern Shrike, are bands carefully scrutinized year after year—even in his case, Ryan puts a unique combination of color bands on each banded shrike’s legs so that he doesn’t actually have to catch them repeatedly to verify their returns.

In the case of Wisdom the Albatross, the hard work and tenacity of one man, Chandler Robbins, was necessary to confirm Wisdom’s age. Leg bands deteriorate over time, and hers has been replaced with a new one several times since 1956. Each time a band is replaced, the old one’s number is recorded, but that provides just one entry in the Bird Banding Lab’s enormous database. Of the very few birds whose leg bands ever need replacing, only a tiny fraction need the replacement replaced even once, much less several times. So there has never been a specific and easy-to-use protocol for tracing replacement leg bands that were replacing already-replaced ones, much less a way to trace them through four or five or even more changes. Chandler Robbins is painstakingly going through the database, tracking each change on the Midway albatross bands, which is how he confirmed in 2001 that this particular bird was, indeed, one of the ones he’d banded in 1956. 

Some of the birds banded then may have moved to more remote islands, and some birds living back then may have eluded capture all along, so we’ll never know if she’s the oldest surviving albatross on Midway Island, much less if Laysan Albatrosses living elsewhere are just as old or older. We don’t even know for sure how old Wisdom was in 1956—all we know is that at that time she was nesting, so was a minimum of 5 years old. For all we know, she could have been 10 or 20 at that time.

Next, Wisdom did not give birth to an egg—she laid it—and certainly did not "give birth to a live hatchling" or "birth a chick"—something that would deservedly make headlines. Her chick hatched from an egg on February 3. I do occasionally refer to a bird’s hatch-out day as its birthday, but that’s stretching the truth by quite a bit. Some reptiles produce extremely thin-shelled eggs retained in the mother’s body until they hatch and the young can crawl out. That may be interpreted by some as giving birth, but birds don't do anything like this. I don’t know if headline writers belong to a group of people that tuned out their elementary and high school biology classes, but if they were daydreaming while looking out the window, I wish they’d have noticed the birds out there. 

It’s thrilling that the news media recognize a good story when they see it, and most of the headlines and stories presented the news accurately, but it’s depressing to have found yet more examples of the media’s lack of understanding of such a basic part of natural history and biology. I wish that when people taught kids about "the birds and the bees," they'd actually teach them something about the birds and the bees. 


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