By: Chance Hines
10/5/23

While temperatures outside continue soaring, the shortening days and falling leaves remind us that autumn is nearing. This time of year also finds many of us in coastal areas checking those long-term forecasts hoping tropical storm activity doesn’t affect weekend plans to take advantage of the last warm weather of the season.

Unfortunately, birds are unable to check out the local news or internet for long-term weather forecasts despite making plans for long-distance trips. Some of these trips include non-stop flights over thousands of miles. Many of these miles are also over the open ocean, far from land that might be needed for an emergency landing.

For the past two years CCB has collaborated with The Nature Conservancy in an effort to capture and tag whimbrels along their southbound migration during autumn. During late summer, these birds travel more than a thousand miles from their breeding grounds near the Hudson Bay to reach the seaside lagoon system of Virginia’s eastern shore. This part of Virginia is an integral staging location where birds spend up to four weeks to accumulate fuel for the trans-Atlantic leg of their southbound journeys during autumn. Once they leave the shore, they will often fly continuously for four days to reach South America.

Past CCB tracking efforts have revealed that whimbrel do encounter storms during their flights and birds typically change course to avoid the worst of the storm or land on islands that are nearby. Birds using the migratory pathway that includes the eastern shore were five times more likely to encounter a storm than those that use a more northern departure location in Atlantic Canada to cross the ocean further to the east. Birds that depart from Atlantic Canada require an additional two days of non-stop flight time over the open ocean.  It appears that, for birds flying through Virginia, the tradeoff is an increase in exposure to tropical storms in exchange for a shorter flight.

This strategy of shorter flight times pays off in years with little tropical storm activity. The 2022 hurricane season brought the fewest tropical storms to the Atlantic Basin since 2015 and we did not document a single storm interaction for birds that we tagged. However, it seems that 2023 will be a different tale. We have nearly reached the total number of tropical storms from 2022 with more than two months of hurricane season to go and tropical activity has already affected at least three of the sixteen birds we tagged.

Unlike previously described interactions where birds either maneuvered around storms or were grounded on Caribbean Islands, whimbrels that encountered storm after departing the shore in 2023 all turned back toward their departure locations to refuel and try again. One whimbrel flagged “CP9” traveled nearly 1,500 miles over the ocean before the ominous winds and rains associated with hurricane Franklin spurred a U-turn back to the eastern shore to replenish those spent fuel reserves. Another bird, whimbrel CP8, met Hurricane Franklin a couple days later about 800 miles after departing the eastern shore and quickly headed back from where it initially departed. The third bird, CM0, only had to fly 150 miles before being turned back to the Outer Banks by Hurricane Idalia.

Unfortunately, scientists expect the frequency and intensity of tropical storms to increase in the coming decades.  Hopefully research like this will help us understand how greater tropical storm activity will affect whimbrels and other shorebird species.