Tag Archives: poleward

The Limpkin explosion: Like an invasive species in a changed world

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When this field guide was published in 1966, it was clear from the range map that, if I wanted to see a Limpkin in the US, I had to go to Florida.

Limpkin species account from 1966 Golden Field Guide.
The Limpkin range map from this popular 1966 field guide.

Growing up as a kid birder in the 1970s, this was one of my first field guides. I did not see my first Limpkin until decades later, in 2005. At that time, this freshwater snail and mussel specialist was still largely a Florida bird, with only a scattering of records north of their usual range.

Limpkin records north of Charleston, SC up thru 2015
Extra-limital records up thru 2015 (on eBird).

Between 1956 and 2015, eBird shows only 18 Limpkin sightings north of Charleston, South Carolina, though presumably some historical records have not been entered. Suffice it to say, a Limpkin in this region was a rarity. There were no Gulf Coast records in Texas, Louisiana, Mississippi, or Alabama, and only a few in the Florida panhandle west of the Tallahassee area.

Suddenly, all this changed. 2019 saw records from Illinois, Ohio, Virginia, and coastal Louisiana, in addition to dozens of records from Alabama, Georgia, and South Carolina. 2020 and 2021 added a scattering of records from Texas to Minnesota(!) to Maryland.

Extralimital Limpkin records across the eastern US in 2022 and 2023 (so far)
The remarkable Limpkin invasion so far.

In 2022, they simply exploded, with first state records across much of the continent. 2023 looks like it is picking up where last year left off.

This kind of rapid range expansion is typically seen in invasive species who are introduced into a new ecosystem. They either die out or explode. The Limpkin invasion, however, is not because they have just arrived in Florida — they are a native species — but because the ecosystem north of Florida has been transformed by a warming climate. It is as if they have landed on a new continent. They are following food — an invasive apple snail, as well as freshwater mussels.

This kind of poleward range expansion is predicted with climate change and has already been documented in hundreds of species. See, for example, my posts here:

And these scientific papers:

  •  Amano et al. 2020. Responses of global waterbird populations to climate change vary with latitude. 10: 959-964.Chen et al. 2011. Rapid range shifts of species associated with high levels of climate warming. Science 333 (6045): 1024-1026.
  • Devictor et al 2008. Birds are tracking climate warming, but not fast enough. Proc. R. Soc. B 275, 2743–2748.
  • Hitch and Leberg. 2007. Breeding distributions of North American bird species moving north as a result of climate change. Conservation Biology 21(2): 534-9.
  • Langham et al 2015. Conservation status of North American birds in the face of future climate change. PLoS ONE 10(9): e0135350.
  • La Sorte, F.A., and F.R. Thompson III. 2007. Poleward shifts in winter ranges of North American birds. Ecology 88(7):1803–1812.
  • La Sorte FA and Jetz W. 2012.  Tracking of climatic niche boundaries under recent climate change.  J Anim Ecol. 81(4): 914-25.
  • Prince, K. and B. Zuckerberg. 2015. Climate change in our backyards: the reshuffling of North America’s winter bird communities. Global Change Biology 21(2): 572-585.
  • Stephens et al 2016. Consistent response of bird populations to climate change on two continents. Science 352(6281): 84-7.
  • Virkkala, R. and A. Lehikoinen 2014. Patterns of climate-induced density shifts of species: poleward shifts faster in northern boreal birds than in southern birds. Global Change Biology 20: 2995–3003.

[A more complete list of academic papers about birds and climate change, with highlighted abstracts, is available in the Documents section of the Birds and Climate Change Facebook group.]

Like many birds with expanding ranges, Limpkins have been slowly recovering for decades from historic habitat impacts. There are historic records (from the 1800s) from Georgia, which they did not occupy again meaningfully until 1994. Likewise, expansion into the Florida panhandle was not until the late 1980s. This fits the typical climate change pattern, with ecosystem changes beginning in the mid to late 1980s. Range expansions, however, can be variable, with different species crossing ecological and climatological thresholds at different times.

eBird status map for Limpkin
The current eBird status map for Limpkins shows them as regular from Houston to North Carolina.

Like most of the species shifting their ranges, Limpkins are generally non-migratory, though may have some seasonal movements based on water levels and foraging conditions. Most the recent northern records have been in summer. It is not known if these birds return south in fall, or die, not being able to withstand the winter. That said, they are undoubtedly establishing year-round presence in southern Louisiana (where the first state record was in 2018), and likely from Texas to South Carolina. There are recent winter records from Iowa, Ohio, Oklahoma, Kentucky, and Virginia.

Limpkin southward expansion in Argentina and Chile
The Limpkin may be one of the few species expanding poleward in both directions.

The Limpkin also ranges south into Central and South America. Its scientific name is Aramus guaranauna, the latter part being the Tupí name for it. Until 2018, it did not occur south of Bahia Blanca, Argentina (at least not in eBird). Its core range ended closer to Buenos Aires. However, with a record in 2018 and four more in 2020 (based on eBird, which is used less in South America), it has spread up to 700 miles south, mimicking its poleward spread in North America. Northern Ohio is also about 700 miles from the Limpkin’s core range in Florida. The southernmost record, found dead at Puerto Deseado, Argentina, is at 47.8 degrees south latitude. The northernmost record, just north of Minneapolis, is at 45.2 north latitude. Like a true invasive species, one even crossed the Andes!

Limpkins are not the only waterbird associated with Southeast wetlands that are expanding north. Birders have noticed northward range expansions among the following:

  • White Ibis
  • Neotropic Cormorant
  • Black-bellied Whistling Duck
  • Purple Gallinule
  • Anhinga
  • Roseate Spoonbill
  • and even Snail Kite, Swallow-tailed Kite, and Mississippi Kite
Limpkin

Many of these are actually declining in Florida (or Louisiana) as they increase in the north.

Indigenous Americans relied on observations of nature to provide information about weather, or when certain plants could be planted or harvested, or when certain fish or game were available. An Anhinga in New York, a Purple Gallinule in Ohio, White Ibises nesting in New Jersey, all of which have happened in this year – would be portents of change – or doom.

Miners kept canaries in coal mines to monitor the atmosphere. A sick or dead canary meant dangerous conditions in the mine. But imagine their surprise if their mine was suddenly invaded by a hundred canaries. That would mean something was amiss outside. Limpkins are becoming those canaries.

BREAKING: One day after posting this, a first record for Ontario, Canada.

UPDATE IN JULY 2023: Limpkin has reached Pennsylvania.

Eastern Towhee: Can the white-eyed subspecies survive even 1.5C climate change?

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Pale-eyed and red-eyed forms diverged approximately 18,000 years ago.
Photo by Melissa James/Macauley Library.
eBird abundance map for Eastern Towhee. It is resident in the southeast, but expands north in summer.

The Eastern Towhee, a bird of scrub and thickets, is a common resident in the southeast United States. One subspecies migrates north in summer.

They are a prime example of a species that is considered “Least Concern” by the International Union for Conservation of Nature (IUCN), but “High Risk” in National Audubon’s assessment of birds under climate change. In their 3.0 C scenario, they predict it would lose 83% of its current breeding range, while gaining only 23%.

This is National Audubon’s projection for the Eastern Towhee’s breeding range under just a 1.5C scenario. This would spell extinction for the white-eyed birds of Florida and the deep South.
Their winter range is not anticipated to change much.

These projections are consistent with recent literature showing poleward shifts of species ranges– of the northern edge of their range, of the southern edge, and of their range’s geographic center. The predictions for Eastern Towhee are among the most dramatic.

Recent research also suggests that non-migratory and short-distance migrants are more adaptable to climate change than are long-distance migrants, and more able to shift their ranges. Indeed, we are already seeing that with Eastern Towhee. The Audubon projections appear to be in progress.

Based on Breeding Bird Survey (BBS) data, the Eastern Towhee breeding population in Florida has declined over 50% since the late 1990s. The timing of this is consistent with worldwide ecological shifts which began in the mid-1980s.

The white-eyed subspecies appears to be already in trouble. eBirders in Florida in May and June are encountering the species half as often as they were just six years earlier.

eBird data from Florida, focusing on frequency of lists reporting the species during the May-June period, shows that the maximum frequency has fallen from 18.3% in 2015 to 8.6% in 2021.

Not all range shifts are due to climate. As a scrub specialist, the Eastern Towhee prefers habitat that is in the act of regrowth, such as after a fire or being cleared. But they don’t want a forest either. To quote the Birds of the World species account for Eastern Towhee: “As farmland is abandoned, successional changes produce suitable midseral habitats that towhees favor, and their numbers increase. But, successional time is against towhees, and their numbers decrease as seres age.” That may be the explanation for the Georgia data (orange dots), which show a decline in the late 60s and early 70s, possibly due to forest growth or land clearance for development, and then a leveling off.  

As the climate warms, many species are expanding north and/or declining in the southern part of their range. But these need not happen simultaneously. Opportunities for suitable habitat may open doors in the north, and doors may close in the south, at different times. There is evidence of Eastern Towhee expansion in Minnesota, but look at the vertical axis; it does not compare with the losses in Florida.

In Florida, the white-eyed subspecies faces extinction based on National Audubon’s 1.5C scenario. They appear to have declined dramatically in the past two decades.

Photo from National Audubon website that provides range change projections under 1.5C, 2.0C, and 3.0C scenarios.

For more on climate change impacts on birds, I invite you to join the Birds and Climate Change Facebook group.