Consider the Birds of the Air: These Songbirds Predict Hurricanes

November 5, 2019


Every Animal Knows more than You do. – Chief Joseph

Will life be gone before we even begin to understand it?


WILMINGTON, Del. – This year, a little bird signaled a Delaware researcher that the 2019 tropical storm season in the Atlantic Ocean was going to be more active than normal.

“If you think about it, it makes a lot of sense,” said Christopher Heckscher of Delaware State University, who found the link between veery thrushes and tropical storm activity.

“These birds have evolved in concert with storms in the fall, during their migratory period for, theoretically, thousands of years if not more. It would make sense that they would, at some point, get in sync with the climate at a larger global scale.”

For two decades, Heckscher has been studying Delaware’s densest population of veery thrushes, a cinnamon-colored songbird with a spotted chest that migrates every spring from the southern Amazon basin to northern breeding grounds that stretch from Delaware to Canada.

Over the years he has watched and tracked one population of veeries nestling into the forests of White Clay Creek State Park each spring. Even though the species travels thousands of miles for this moment, they only ever raise one clutch, or one successful nest of usually two to four chicks.

“I started to notice that in some years the birds were stopping their breeding season earlier than other years,” the ornithologist, entomologist and environmental science professor said.

He began to wonder why after a few years of shorter breeding seasons. Did they not have enough food? Was it because the weather was too dry or too hot?

Eventually, he started looking at what advantage the birds would have by shortening their nesting season. That’s when he thought to look at tropical storm activity, which occurs along their long migratory route.

“It turns out that in years they stop breeding earlier, there’s more tropical storm activity on their migration route,” Heckscher said. “I thought of that idea, I tested the hypothesis, I looked at the data, but I really wasn’t expecting there to be any relationship there.

“And it was a really strong relationship.”

Nearly 20 years of data showed Heckscher that not only does the length of the veery’s breeding season relate to future tropical storm activity, but the average number of eggs in each nest could also signal whether the season will be normal, slow or overly active. He found that females produce more eggs when an active hurricane season is in store.

“The chances of this relationship being coincidental, in my opinion, are pretty small,” he said. “We don’t know for sure that the relationship is real, but there is a relationship between what the birds are doing and the following tropical storm season.”

In late May, NOAA predicted that this year’s Atlantic tropical storm season, which lasts from June 1 to Nov. 30, would be near normal. It called for up to 15 named storms, two to four of which would become major hurricanes.

Meanwhile, the veery thrush data from this spring indicated the season would be a bit more active than normal.

By their next update in August, NOAA changed its prediction for the season and increased the chances of an above-normal season with up to 17 named storms. As of Nov. 1, there have been 17 named storms and three major hurricanes.

The birds had it right all along.

“Which is pretty incredible if you think about it because these birds, the timing of their breeding season is determined in May and June, and that storm activity is happening in September, October, November,” Heckscher said.

Nature Scientific Reports –
A Nearctic-Neotropical Migratory Songbird’s Nesting Phenology and Clutch Size are Predictors of Accumulated Cyclone Energy:

The breeding season phenology of Nearctic-Neotropical migratory songbirds is constrained by subsequent seasons resulting in single-brooded behavior (one successful clutch per year) in some species. Early cessation of the nesting season prior to an active hurricane season will allow for behavioral plasticity during a physiologically challenging migration. Hurricane activity shows a high degree of inter-annual variability. I show that a single-brooded Nearctic-breeding species’ (Catharus fuscescens) nesting phenology and clutch size are significant predictors of Accumulated Cyclone Energy. The most skilled predictive model includes both mean clutch initiation date and mean clutch size (R2 = 0.84). Spearman rank correlation coefficients for both predictors with subsequent major hurricanes (1998–2016) are −0.55 and 0.52, respectively. Therefore, May and June clutch initiation and clutch size showed stronger correlations with subsequent hurricanes than early season (prior to August) meteorological predictions widely publicized by CSU, NOAA, and TSR (≤0.45, 2003–2014). Rainfall anomalies in the southern Amazon basin associated with ENSO cycles are a possible proximate cue affecting phenology and clutch size. This discovery potentially has far-reaching ornithological, meteorological, and social implications and shows that tropical storms significantly constrain breeding season behavior providing renewed evidence that hurricane activity is a primary factor regulating Nearctic-Neotropical migratory songbird populations.


5 Responses to “Consider the Birds of the Air: These Songbirds Predict Hurricanes”

  1. […] via Consider the Birds of the Air: These Songbirds Predict Hurricanes | Climate Denial Crock of the Week […]

  2. Bryson Brown Says:

    Of course there are plenty of climate deniers who are also evolution deniers…

  3. doldrom Says:

    There are possibly thousands of such clues of which animals and nomadic cultures (now extinct) were aware of. Of course there must be something orchestrating such awareness, which means they could be important leads for researchers looking to understand weather/climate science and mechanisms. Fascinating.

  4. rhymeswithgoalie Says:

    Those that preferred to breed in the wrong season were not successful at reproducing? What a concept!

  5. […] Peter Sinclair, Climate Denial Crock of the Week […]

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