In Part 3 of our look back at the 2010s, we’re examining how the climate crisis is affecting birds and how our understanding of climate change has developed in the last decade.
I asked Brooke Bateman, senior climate scientist at the National Audubon Society, to compare what we know about climate change and birds now with what we knew 10 years ago. Here’s her reply:
“From the careful observation of bird enthusiasts and community scientists, we have known for a few decades now that birds are already responding to climate change. Long-term records have provided insights in how bird species are shifting their migration timing earlier, while others are laying eggs earlier than they used to. However, in the last decade we have a more complete picture of this story. We now know that migration timing is shifting not just for a few species, but for North American birds as a whole, and at a steady rate due to climate change.
“This knowledge is available to us now as weather radars have enabled scientists to study hundreds of species and billions of birds over time. Birds are also shrinking in body size as the climate has been warming, and they’re growing longer wings to keep pace with the changes and migration pressures. It’s not only migrants, but also backyard birds, where studies show that the birds at our feeders are reshuffling. Southern warm-adapted species like the Chipping Sparrow and Carolina Wren are able to expand northward due to milder winters. This was all uncovered from data collected by community scientists, a data collection powerhouse that has surged in recent years.
“In the last decade, due to a more comprehensive understanding of climate change and better data availability, we have learned that some species have lost entire parts of their range to climate change already, such as the Rusty Blackbird with a range that has retracted 143 km northward. Entire communities are becoming disrupted. The Broad-tailed Hummingbird’s migration is now out of sync with its glacier lily food resource, arriving after the blooms have finished, and climate change is causing mass die-offs in seabirds more frequently, as oceans warm and ecosystems collapse.
“We are also armed with a more solid understanding of how birds will continue to be affected by climate change. Audubon’s Survival by Degrees report provides a comprehensive look at the vulnerability of 389 North American bird species to climate change, with each species losing large parts of their range, and revealing two-thirds of the species are at risk of extinction from climate change if we don’t take action now. The advances in climate modeling, technology and computing, modeling methodologies, and bird occurrence databases over the last decade have made a continental-scale analysis of this scale feasible.”
Trends in rare-bird sightings
And I asked field-guide author and BirdWatching Contributing Editor Kenn Kaufman if any trends in rare-bird sightings over the last 10 years might be specifically tied to climate change. Here is what he said:
“Certainly, climate change is having an impact on overall bird distribution, as we continue to see ranges shifting northward — with many southern species advancing and many northern birds retreating. It’s probably having a negative effect on the populations of many boreal breeders, as their total available habitat shrinks. But it’s harder to link individual rarity sightings to climate change. The most noteworthy vagrants are so seemingly random, their discovery is so subject to chance, that trends would be hard to detect.
“More rarities are being found now, but a big part of that would be owing to the increasing numbers of birders. Photography and the Internet have played a big part also, as many, many rarities have been documented because some casual birder saw something odd and snapped a photo and posted it online. In the past, most such finds would have gone unidentified and unremarked. To know if overall numbers of birds straying out of range are changing, we’d have to look at long-term data from a site with consistent effort, like the Farallon Islands (off California) or the tip of Ontario’s Long Point.
“But if individual rarities are hard to connect to climate change, there are some shifts in status of former rarities that seem more straightforward. A couple of the best examples involve boobies and whistling-ducks.
“If you go back a couple of decades, boobies of any species were extremely rare in California’s offshore waters (although Blue-footed Boobies would occasionally show up at Salton Sea). Now Brown Boobies are being seen regularly year-round off California, in numbers, and there are also regular sightings of Masked, Blue-footed, and even Nazca and Red-footed Boobies. They’ve all been seen multiple times at multiple offshore locations in the last couple of years. It’s really an astounding change. Farther east, Brown Boobies are being seen along and off the Atlantic and Gulf Coasts, from Newfoundland to Texas, and on numerous inland lakes north at least to Massachusetts, Indiana, and Nebraska. Locally many of these are still regarded as great rarities, but the cumulative totals are nothing short of amazing. Since boobies are warm-water seabirds, their spread seems naturally tied to the warming climate and warming oceans.
“Whistling-ducks provide another great example. Black-bellied Whistling-Ducks used to be a specialty of southern Texas, but in recent years they have wandered all over the map, especially east of the Rockies. I saw them in New Jersey and Ohio this year, and I didn’t have to go more than a mile out of my way to do so. This year’s reports included a flock of 6 in Nova Scotia, a flock of 9 in Quebec, a flock of 10 in northern Illinois, and a flock of 8 in Wisconsin, just to name a few of the northernmost records from this year alone. The total number of individuals found north of the Gulf Coast this year was probably in the hundreds.
“Fulvous Whistling-Ducks haven’t expanded as much, but they’ve been moving up the Mississippi River Valley. This year, multiple pairs of both Black-bellied and Fulvous Whistling-Ducks nested in southwestern Illinois! Again, this is something I would have considered unbelievable just a few years ago. Whistling-ducks showing up in the north are still considered local rarities, but they’re clearly a part of this much larger pattern. And since these are tropical ducks, the warming climate seems like a logical element in their spread.
“The latest version from this year of Audubon’s birds-and-climate work makes some really important projections about what will happen to bird distribution as the climate warms up. Some of the predictions may look extreme at first glance, but they’re no more extreme than the examples I just mentioned, things that we know are already happening. So, I hope that birders will look at the Audubon climate work and take it seriously.”