The hurricane season of 2020 has already broken many records – most named storms and the earliest seven storms have made landfall in the U.S., among others – and the season isn’t over yet. Hurricanes are expected to increase in intensity as a result of climate change, and while hurricanes may become less frequent overall, the most intense storms will actually become more common. This could be devastating for vulnerable, low-lying beachfront communities, but coastal birds and habitats are also at risk.
Hurricanes and tropical storms can cause mass mortality of staging, migrating, and nesting birds. In 2005, Hurricane Wilma carried thousands of birds – including over 700 Chimney Swifts – as far as Western Europe. The next year, Chimney Swift populations were half of what they were before the storm. Hurricane Bob passed over a major Roseate Tern migratory staging area in August 1991, and was linked to a 17% decline in nesting pairs the next year. Sooty Tern mortality in the Atlantic Ocean is higher in years with more frequent and intense hurricanes. Hurricanes even affect waterbirds nesting far inland: Cyclone Fani demolished tern and shorebird nests on a river sandbar over 100km from the ocean.
However, hurricanes more commonly affect birds indirectly by damaging the habitats they rely on for nesting, foraging, and roosting. Hurricanes change beach profiles, redistributing sand from dunes to beaches. While on some beaches and barrier islands critical nesting beaches are lost, in other places nesting and foraging habitats are increased by fresh sand deposition. Snowy Plovers prefer early successional habitat, and as a result they nest in areas frequently impacted by hurricanes. As a result, this species will be negatively impacted if hurricane frequency declines, as predicted. Other beach-nesting birds, such as Brown Pelicans and Black Skimmers, declined following the one-two punch of Hurricanes Gustav and Ike to Louisiana’s coasts in 2008, which washed away nesting habitat.
Forest birds are threatened by the increasing intensity of hurricanes. Hurricanes wreak havoc on forest structure, creating canopy gaps, removing limbs and vegetation, and stressing the trees that remain standing. Consequently, fruit- and nectar-eating birds decline following hurricanes, while insectivores that forage aerially or on standing dead trees increase in abundance. For example, critically endangered West Indian Woodpecker populations in the Bahamas initially declined then rebounded within three years of hurricanes. Yet birds that are disturbance-sensitive or require intact forest canopies declined after rare storm damage in a Chiapan cloud forest.
The good news is that many bird populations are highly resilient to hurricanes. While richness and abundance will decline in the months and years following storms, populations recover within 20 years on average. In some cases, populations recover even more quickly – or are minimally affected in the first place. Understory forest birds in Cozumel returned to pre-storm abundances a year following dual hurricanes. In the northeastern U.S., nest survival of marsh birds following Hurricane Sandy was similar to the rates prior to the storm. Frequently, hurricane damage will displace birds to habitats unaffected by the storm, but if the birds have room to move – and if another hurricane doesn’t hit the region too soon – birds will eventually return. Additionally, restoration tactics like beach renourishment can help raise nesting elevation out of the reach of storm surges, protecting beach-nesting birds. By protecting and restoring habitats, we can help ensure that coastal birds weather the storms to come.