21 Jun 2019

After the storm: can this rediscovered bird recover?

Amongst the destruction and tragedy on Grand Bahama caused by Hurricane Matthew, there is an untold story of a rediscovered, but very threatened bird with a potential population of just two.

By Claudia Hermes and Margaret Sessa-Hawkins

How low can a bird species’ population drop and still be saved from extinction? It’s an interesting theoretical question, and it became more than an academic one for scientists and conservationists last summer, when the Bahama Nuthatch Sitta insularis, a bird feared extinct, was rediscovered.

Prior to the rediscovery, the nuthatch had not  been seen since Hurricane Matthew ripped through Grand Bahama – the island on which the bird is endemic – in June of 2016. Two years on from the carnage, two students from the University of East Anglia, working in conjunction with BirdLife International and the Bahamas National Trust (BirdLife Partner) went on an expedition to catch sight of the bird.

“We had been scouring the forest for about six weeks, and had almost lost hope,” says Matthew Gardner of the rediscovery. “At that point we’d walked about 400 kilometres. Then, I suddenly heard its distinctive call and saw the unmistakable shape of a nuthatch descending towards me. I shouted with joy, I was ecstatic!”

The world was ecstatic along with him. The news made international headlines, and the ornithological world celebrated the rediscovery of the Bahama Nuthatch. But are the celebrations warranted? Gardner and his partner, David Pereira, saw the Bahama Nuthatch six times throughout their three-month survey, but they never saw two birds together, leading them to believe there may only be one individual left. A team of Bahamian students, led by Zeko McKenzie of Loma Linda University, independently recorded five sighting of the nuthatch in the same forest, and believe they may have seen two birds together. With only one or two Bahama Nuthatches left though, is it possible for the bird to make a comeback?

It’s not unprecedented for a species to dodge extinction even with population numbers in the single digits. Perhaps the most famous case is the Black Robin Petroica traversi. Endemic to Chatham Island, off New Zealand, the robin’s population had crashed to only five individuals in 1980. Remarkably, there was only one adult female among these birds. But even though the Black Robin seemed doomed to extinction, conservationists didn’t give up. They moved the remaining individuals to a nearby predator-free island, where the population finally increased when the robin’s eggs were given to New Zealand Tomtits Petroica macrocephala, which acted as foster parents while the robins continued to produce more eggs. There are around 250 Black Robins alive today, meaning the species is still Endangered, but also that it has made an incredible recovery. And all of them are a descendant of that one surviving female in the 1980s, “Old Blue”.

Can these successes be replicated with the Bahama Nuthatch though? Whether a bird can make a comeback depends heavily on the ecology of the individual species, as well as the reasons for its decline. One problem for the nuthatch may be its sex ratio. In bird species with low populations, males tend to far outnumber females, mainly due to to higher female mortality. If there truly are only two nuthatches left in the wild, they may all be males. There may be another reason it’s hard for the nuthatch to replicate the success other birds with low populations have had, though. In other cases, for every species pulled back from the verge of extinction, the exact causes of the initial population crash was known. On this particular issue, the Bahama Nuthatch may run into trouble.

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Overall, there is not much known about the Bahama Nuthatch – and the little we know isworrisome: just fifteen years ago this species, while hardly thriving, was far from the precarious position it finds itself in today. In 2004, a few hundred individuals were recorded on Grand Bahama. By 2007 though, only 23 individuals were spotted; the suspected drivers of this steep demise were invasive species and habitat loss. The species only lives in forests of Caribbean Pine. Since the 1950s these have been cleared rapidly on Grand Bahama in order to create space for roads, housing developments and tourist resorts. Without widespread pine forests, the nuthatch has limited places to nest, and will not be able to find food. Invasive predators like snakes, cats and raccoons also likely contribute to the threats facing the bird. When Hurricane Matthew swept through the island in 2016, it was feared that the storm had wiped out an already dwindling population.

What makes things really worrying for the nuthatch is that it is unclear what precisely caused the population crash occuring even before the hurricane hit. Therefore, it is not possible to directly address the underlying cause of decline with conservation measures. Given this information, bringing back the Bahama Nuthatch would be extremely difficult. This does not mean conservationists are giving up though. The nuthatch has previously been found mostly around an area known as Lucayan Estates - small tracts of both private and corporate land that remain mostly undeveloped. The protection and restoration of Caribbean Pine forests in this area would be key to bringing the Bahama Nuthatch back.