American Birding Podcast



Caribbean Hurricanes and Birds: Interview with Dr. Joseph Wunderle

In 2017, the Caribbean was hit with several powerful hurricanes, most notably Irma and Maria, both Category 5 storms.  The April 2018 issue of Birding will include an article I wrote about the impact of hurricanes on Caribbean birds.

Dr. Joseph M. Wunderle Jr. wrote a number of the key scientific papers on this subject and he was kind enough to talk to me during the writing of the article.  Dr. Wunderle is a scientist at the International Institute of Tropical Forestry (IITF), a part of the U.S. Forest Service.  The IITF has been conducting ecological research throughout the Caribbean since the 1930s, much of it in El Yunque NF (also known as the Luquillo Experimental Forest) in eastern Puerto Rico.

Dr. Wunderle lives and works in Puerto Rico and has been studying the behavior and conservation biology of Neotropical birds and Nearctic-Neotropical migrant birds for decades.  He moved to the island in 1982 to teach at the University of Puerto Rico and joined IITF in 1988. His current research includes wintering Kirtland’s Warblers.

As publication of the article approaches, I checked back in with Dr. Wunderle and he was kind enough to answer some questions via email.  His lightly edited responses are below, and I thank him for his continuing assistance.


Q:  Although they are a regular risk in the Caribbean, most of us have never experienced a hurricane.   Can you provide some sense of what that is like?

A:  The sounds are the most un-nerving aspects of hurricanes as one rides out the storm at home, even in a sturdy cement block home, with windows covered in metal storm shutters.  The winds and wind-blown rains have been likened by some to the roar of a fast train as it passes nearby.

Many of the sounds can be extremely unsettling, especially when we’re inside with windows shuttered and can’t see the source of the sound and therefore we can only imagine the worst-case scenarios.  The snap and crackle of breaking branches and trunks and crashing sounds as branches and trunks fall on the ground or walls, buildings, or vehicles are disturbing. The occasional crash of a hard item such as a tile or other piece of building material colliding against the storm shutters adds to the cacophony of sounds.  The rains arrive in bands or intense showers so there are periods with moderate or light rains punctuated by heavy rains driven almost horizontal by wind gusts.

Even with good tight doors and storm shutters, water can be forced through cracks or openings, so mopping up water is a frequent activity.  Even a concrete house shudders with the strongest wind gusts. With time, the closed house becomes hot and muggy. Thus, getting a good night’s sleep is a challenge, even with ear plugs to deaden the sounds.

Q:  Can you describe the state of the island after Maria?  

A:  I was not on the island for the arrival of Maria, but returned three weeks later, so much of my account of the immediate aftermath comes from friends and neighbors as well as my personal experience with other hurricanes.

The immediate aftermath, even with prior hurricane experience, is usually a shock, because of the sudden transformation.  What once was mostly green is gone or on the ground and many of the vertical stems are leaning or on the ground. The post-storm aftermath reminds one of a leafless deciduous forest in winter.  The smell of decaying vegetation becomes apparent quickly after the storm. Where green was the dominant color theme, gray and brown now predominate. With the leaves gone, we discover buildings which we never knew existed on the hillsides.  

Given fallen trees, limbs, utility poles and downed phone and electric lines covering the highways, access and driving is impossible and challenging even on foot.  Depending on strength of the hurricane, it may take days for paths to be cleared to allow transit, assuming there are no major landslides. Landslides in the mountainous areas prevented transit and isolated so many communities, making rescue and recovery efforts so very challenging.  The absence of electricity, communications, and water add to the challenges.

Once personal stores of water, food, and generator fuel become exhausted, people leave home, crowding highways, stores, and gas stations.  Waiting in long lines for necessities becomes a way of life.

Q:  Irma passed near Puerto Rico on September 6, 2017, and Maria directly hit the island on September 20, 2017.  How are the forests and other habitats recovering, approximately six months later?

A:  My Forest Service and university colleagues and I have done some informal assessments of the conditions of the forests in the Luquillo Mountains using satellite imagery as well as by driving and walking (or more precisely climbing, crawling, scrambling over fallen branches and fallen or leaning trees).  

Surprising to us is how my tree stems are still vertical, or almost vertical, despite the intensity of storm winds.  As expected, there are areas of blow downs of trees, including some palms, which tend to be resistant to high winds, possibly because they readily shed their fronds. The frondless palms, especially at higher elevations were especially notable, as were the almost complete absence of palm fruits, which are normally abundant at this time of year. The loss of sierra palm fruits suggests a food shortage for those dependent on the fruits for breeding, especially the Puerto Rican Parrot and Pearly-eyed Thrasher.

A view from Bano del Oro, El Yunque National Forest

Despite the radical transformation, signs of recovery, at least in the lowlands, were apparent within a couple of months, as new leaves sprouted from remaining branches and even on tree trunks, resulting in a peculiar bottle brush appearance in many tree species.  New vine growth was perceptible after a month as vines began to cover fallen debris and started to ascend tree trunks. In the absence of a canopy, increased sunlight, at least on shrubs in forest edges or openings contributed to rapid leaf-out followed by flowering and fruiting.  

At the higher elevations, however, recovery is slower due to the slow growth typical of most high-elevation plants, but even there, tree ferns grew new fronds after two months.  Fast growing early succession plants, typical of forest edge or tree fall gaps, such as the trumpet tree are now sprouting and growing and will dominate disturbed areas of the forest, whereas the larger old-growth trees, typical of mature forest, will take many years to replace lost branches and close the forest canopy.

Q:  And what about the birds in El Yunque?  

A:  Immediately after Maria, my Forest Service colleagues found dead Bananaquits, Pearly-eyed Thrashers, and Red-legged Thrushes in El Yunque while observers in urban areas reported dead Greater Antillean Grackles and Rock Pigeons.  Of the survivors, many were easier to detect in the hurricane’s aftermath, given absence of foliage, and canopy dwellers were also easily spotted as they foraged at eye level in the fallen canopy remnants. Species such as the Puerto Rican Woodpecker, Puerto Rican Lizard Cuckoo and Puerto Rican Tody vocalized more frequently than normal, perhaps because they now could easily see neighbors or intruders formerly obscured by the foliage.  

El Yunque Rock, in El Yunque National Forest, previously surrounded by old growth forest.

In contrast, normally noisy and social, Puerto Rican Tanagers were silent as they foraged alone.  It appeared that most birds were ranging further and foraging more intensively than normal, and sometimes feeding in unusual locations, such as ground foraging by Puerto Rican Parrots, a first for this canopy species documented in a photo on the U.S. Fish and Wildlife Service’s parrot website.  Even now, almost six months after Maria, many birds, including the parrot, are moving too widely to obtain accurate population estimates, but we expect that wandering birds will settle down in the coming months, as vegetation and food resources recover.

Q:  You were involved in the Fajardo Christmas Bird Count.  (Fajardo is located near the northeastern corner of Puerto Rico.)  How do those numbers compare to historical counts?

A:  Our 24th Fajardo Christmas Bird Count (FCBC) was conducted on 17 December 2017, after substantial storm damage and lingering shock and disruptions from Irma (7 Sept.) and Maria (20 Sept.).  Despite extensive defoliation (estimated 50-100%), and loss of branches with some trees felled or snapped, vegetation recovery by count day was well underway, at least for re-growth of leaves and some vines in the lowlands.  

Overall, the post-hurricane 2017 FCBC tallied 1,934 birds of 82 species, both of which were low counts for past FCBCs (e.g., 2016 FCBC had 2,579 birds, 97 species).  When corrected for search effort in the field, we found 1.8 species per party hour (ph), a value not much lower than the mean for counts of the previous 10 years and within the range of earlier counts (1.8-2.2 species per ph).  

Palm stand at El Yunque National Forest

In marked contrast, we had only 43 individual birds per ph, which was well below the 10-year mean of 59.6 individuals per ph and outside the 10-year range of previous counts (47.7-68.2 individuals per ph).  Thus, post-hurricane field groups (or parties) encountered new species for their lists at a rate only slightly lower than in previous counts, but encounters of new individual birds were markedly lower than previously.  Thus, not surprisingly after two hurricanes, the number of individual birds was much reduced, although there was considerable variation among species.

Some species or species groups showed marked changes in the post-hurricane FCBC numbers relative to the pre-storm 2016 FCBC.  For example, nectarivorous species as a group (hummingbirds and Bananaquits) showed a dramatic decline in detections, which was not surprising given the loss of flowers to winds.  

In contrast, frugivore/seedeaters showed an increase despite expected declines in fruits and seeds in the hurricane aftermath.  The loss of fruits and seeds may have required some species to actively search widely and hence making them easier to detect in open habitats (Monk Parakeet, Scaly-naped Pigeon, Red-legged Thrush, Pearly-eyed Thrasher and Puerto Rican Oriole), while other frugivore/seedeaters showed decreases possibly due to mortality or movement to other sites on the island (White-crowned Pigeon, Ruddy Quail-Dove, Puerto Rican Bullfinch).  

Thus, the 2017 FCBC coincided with the post-hurricane period when many birds were still wandering in search of resources eliminated or damaged by the hurricanes.  Therefore, the count occurred during a difficult period to evaluate population status. This will require future FCBCs to determine the status of the island’s species after the 2017 hurricanes.  Although there will be substantial differences among bird species in their rates of recovery to pre-hurricane abundance, I remain optimistic that most bird populations will recover as in the aftermath of past hurricanes.

Q:  You have been conducting research on Kirtland’s Warblers on their wintering grounds in The Bahamas for years and have suggested that hurricanes pose short-term risks but potential long-term benefits to that endangered bird.  I think most people think hurricanes are invariably bad for birds, so can you elaborate on the potential upside?

A:  We expect that hurricanes contribute to some mortality of Kirtland’s Warblers (KIWA) on their Bahamas wintering grounds, especially in the winter immediately after a storm when food resources have been lost to high winds, flooding. and salt spray.  Long-term, however, hurricane-induced storm surges may create KIWA habitat by eliminating leaf litter and exposing bare soil where seedlings of two important KIWA fruit plants (black torch, wild sage) may establish.

Our experimental studies of seedling establishment of these two important KIWA fruit plants demonstrate that the seedlings can establish only on bare soil and not on soil covered with leaf litter. Even on exposed soil, seedlings establish only on sunny sites. Consequently, these two KIWA fruit plants are common in coastal areas.  Therefore, storm surges may play an important role in producing habitat for the warbler on its wintering grounds. Other bird species, especially those typical of early successional communities may also see long-term benefit from increased light, which facilitates flowering and fruiting. Woodpeckers can benefit from additional dead trees and branches.

Q:  Hurricanes have a powerful impact on Caribbean ecology and tend to spur scientific research.  Can you describe some of the research at IITF and elsewhere that will assess the impact of Irma and Maria on birds?  

A:  My graduate students from the University of Puerto Rico (UPR) and I are re-sampling sites along an elevation gradient in the El Yunque NF where my IITF colleague, Dr. Wayne Arendt sampled bird populations over a 17-year period before Irma and Maria.  By using Dr. Arendt’s studies as a baseline we will document the rates of recovery of individual bird species and bird communities at elevations along the gradient.

In addition, we are initiating a collaborative study (with U.S. Fish and Wildlife Service and El Yunque NF biologists) on the response of the threatened Elfin-woods Warbler to the hurricanes by assessing population size and distribution relative to various pre-hurricane baseline studies. Also, the response of urban bird populations to hurricanes is being studied by one of my UPR students.  Finally, monitoring, management, and studies are continuing on the endangered Puerto Rican Parrot in El Yunque NF by U.S. Fish and Wildlife Service biologists and their collaborators.


Photos:  Grizelle González, U.S. Forest Service.

For more on hurricane impacts on Caribbean birds, see this episode of the American Birding Podcast with Alvaro Jaramillo.