Hummingbirds on the move: Evolution on fast-forward

by Anders Gyllenhaal
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A few weeks ago, dozens of readers from around the country shared their hummingbird stories on our Facebook page after we ran a post on the growing numbers of the tiny birds that are skipping migration and staying in the U.S. for the winter.

Birdwatchers from Michigan to Texas, Seattle to North Carolina reported seeing the birds stay longer into the fall, and sometimes through the winter in the warmer states. Randell Fleet of Houston seemed to speak for everyone when he said: “I hope they’ll be OK.’’

Ruby-throated Hummingbird

The outpouring made us want to know more about what was going on. So we talked with scientists and researchers around the country who specialize in hummingbirds. The story that emerged, which is running in The News & Observer of Raleigh this week, is not just about the changing migration of hummingbirds.

It’s also a look at modern-day evolution on a fast-forward speed as birds struggle to adjust to their altered environments. The story focuses on North Carolina, because this is where a lot of the action is. But hummingbirds, particularly Ruby-throated and Rufous, are starting to stay the winter all along the southern Atlantic coast and down through the Gulf states.

Hummingbird researcher Susan Campbell explaining how she bands the tiny birds

“It’s a really fascinating subject,’’ said Scott Weidensaul, an author and researcher who’s one of the country’s leading experts on hummingbirds, “one that ties together a couple of important threats, including climate change and the adaptability of birds in the face of change.’’

One part of the story we found particularly intriguing, which we couldn’t delve too deeply into in The N&O piece, is how this break with the migration pattern places a spotlight on exactly how birds adjust – and how a pivot like this can play out for generations to come.

Nobody can say when the first hummingbirds decided to skip the long and arduous fall trip to the tropics. I loved the comment by the Audubon Society’s Geoffrey LeBaron, head of the Christmas bird count, who said: “If you don’t have to fly across the Gulf of Mexico, why do it?’’

Cornell Lab’s migration map shows the usual range of the Ruby-throated Hummingbird. The red is the breeding territory and the blue is the spring migration target.

But the first birds who skipped the migration may have done so by accident. Researchers say that young birds, often on their first migrations, tend to stray far and wide, like teenagers of any species. As they’ve found the climate mild enough for stay through the year, more and more of them join the migration revolt.

What happens next is the interesting part.

Birds that stop short of the tropics will return in the spring to their breeding grounds in the far north. Their new migration routes become part of the genetic instruction they pass along to their offspring. If they happen to mate with another bird that winters in the U.S, the genetics will be straight-forward.

But if they mate with a migrator, the genetics may include mixed messages. “It all depends on who they mate with,’’ said Weidensaul.

Either way, the migration instincts can be muddled and possibly give the birds more leeway, researchers say. As the birds experiment with where they go and what routes they take, they are beginning to form a new routine. As a rule these kinds of  tiny adjustments are the fabric of evolution and are spread over thousands and even millions of years as birds jostle for survival.

The challenge of modern-day changes is they are coming so fast. A major report on migration released two weeks ago by the Cornell Lab of Ornithology and two research universities found evidence that birds have sped up their spring migration cycle over the past 20 years alone by as much as a month to adapt to flowering and insect schedules.

The research also suggests that despite their early spring arrival, some species are nevertheless falling out of sync with the blossoming of plants and insects . That could mean they don’t have the food and nourishment they need to start the breeding season, and eventually determine which birds survive and which don’t.

A female Ruby-throated sips the nectar on a flower on North Carolina’s Outer Banks.

Our Facebook followers, from west and east, who shared their experiences are seeing all kinds of unexpected behaviors on the part of their local hummingbirds.

 Flip O’Reilly, who lives on Vancouver Island, remembers seeing Anna Hummingbirds in the summer only. “Now they’re here year-round!’’ he wrote.

Lewis Miller, who lives in north central Illinois, said Ruby-throated Hummingbirds have been staying into mid-October. “Very unusual for them to be here this late,’’ he said.

Many folks say they keep their feeders out longer to help the hummingbirds. It’s a big part of the relationship between bird lovers and the hummingbird. Some of our Facebook followers go to great lengths on this front. Judy Starks Gargano, who lives in Southwest Michigan, makes her own solution for the 12 feeders she keeps out at the busiest parts of her season.

“By the middle of August, I’m going through a couple of gallons a week.’’

Several people asked whether they should keep their feeders out in the winter, and whether that might tempt birds that should be going south to stay longer than they should.

Brooke Bateman, a climate scientist with the National Audubon Society, said people should use common sense about how long the feed hummingbirds.

In warmer Southern states where the birds are known to be overwintering, it’s fine to keep the feeders out, she said. The western species of hummingbirds can withstand the winter weather, while the dominant eastern species, the Ruby-throated Hummingbird, can only take shorter periods of freezing temperatures.

 

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