Portuguese Society for the Study of Birds
Portuguese Society for the Study of Birds
News Article | July 11, 2017
As we hike through the cool, low-canopied forest along a levada – a centuries-old water canal carved out of the mountainside – our guide talks effusively of a pigeon. It’s the “guardian of the forest” the guide with MB Tours tells me and the other hikers. Known as the Trocaz pigeon, or alternatively the laurel pigeon or the long-toed pigeon, it’s only found here: on the Portuguese island of Madeira. We halt under an ancient laurel tree and the guide explains that the endemic pigeon is vital to Madeira because it disperses many of the plants found in this unique forest ecosystem: the laurisilva. A UNESCO World Heritage Site, the laurisilva – a name that sounds like it was invented by Tolkien – is a relic ecosystem found only in a few places on our planet: the Azores, the Canary Islands, and the largest remnant here in Madeira. Made up largely of laurel trees, it’s an ecosystem that once covered much of southern Europe, some 15-40 million years ago. And it’s home to many species found no-where, including the Trocaz pigeon with its unmistakably silver strips crisscrossing the nape of its neck. “[The Trocaz pigeon] play[s] a determinant role for [the laurisilva’s] balance and expansion,” Catia Gouveia, with the Portuguese Society for the Study of Birds (SPEA) in Madeira, writes to me later. And yet since 2012 the pigeon has been routinely culled on the island by the Forestry Police due to its propensity to raid agricultural fields, especially cabbage plantations and fruit orchards, important crops to the small island. On its website, the government claims the pigeon has “disastrous socio-economic consequences for farmers and, consequently, for the family economy.” This guardian of the forest is seen by many in Madeira as a pest, despite being a species found nowhere else and playing a vital role in keeping the laurisilva vibrant. Madeira in Portuguese means ‘wood.’ When the Portuguese first settled in the 1420s they found an island blanketed in lush forest, specifically, the laurisilva. There were no natives living on Madeira – allowing the Portuguese to settle it without enslaving or exploiting indigenous people as they did in Brazil, Angola, Mozambique and East Timor. Not only was Madeira free of people, but, like a mini-New Zealand, the island also held zero land mammals – no rats, mice, cats, monkeys, dogs, or rabbits – just a few bats (the Azores was the same). Lying over 500 kilometers from the African coast, Madeira – about half the size of Hertfordshire – was simply too far over rough seas for land animals to make the crossing, even haphazardly. The total absence of land mammals allowed the Trocaz pigeon to become the royalty of Madeira. Believed to be descended from common wood pigeons, the Trocaz pigeon found a niche on the island with few predators, no humans and little direct competition. When people arrived, of course, things changed. Most of the forests were chopped down, some replaced with villages and towns, others with crops like cabbage, fruit and vineyards, others with exotic forests like eucalyptus. Today, only about 20 percent of the island remains covered in the laurisilva. In the 1980s the Trocaz pigeon almost went extinct as hunting pushed the population to less than 3,000 animals. Only when hunting was outlawed and the pigeon was added to the Europe-wide Birds Directive in 1986 did the species began to recover. Today its population has reached about 10,000-14,000 individuals. The story was a conservation success – and then some flocks started feasting on crops. When it comes to food, the Trocaz pigeon is an unfussy opportunist. Research has shown that they eat at least 33 plants from the laurel forests. But pigeon colonies living near agricultural areas have also taken a liking to locals’ fruit trees and crops, especially cabbage. When a farmer reports they have problem pigeons, the government urges them to purchase various tools to force the birds away including petrol-fueled ‘bird scares’ that cause loud noises periodically, nets to keep the birds out of certain areas, and holographic tape that scares them off. But where such measure haven’t succeeded, a spokesperson from the government’s Institute of Forests and Nature Conservation said the government was allowed to perform a “correction of the population” by the Forestry Police. In others words, government officials come in and shoot the cabbage-devouring pigeons. The government did not respond to several queries asking how many pigeons have been shot. Gouveia with SEPA said that culling birds protected under the EU Birds Directive should only be allowed in “exceptional cases.” She added that SEPA has not seen “sufficiently detailed studies to date” on what crops are being eaten and “above all” how much farmers are actually losing in economic terms. “This information is important in order to take decisions on other possible measures, including compensation to farmers,” Gouveia said. She said she does not believe that the government has “exhausted” all alternatives before turning to shooting. Nor does SEPA have information on how many farmers have actually tried all the other options before they turn to the government to deal with the problem pigeons. While the Trocaz pigeon is currently listed as least concern that doesn’t mean it is at zero risk of extinction. Already, humans have eradicated a population that once lived on the neighboring island of Porto Santo. Now, it is a bird surviving on a single island with a population that, while stable, isn’t especially large. There are more people living in the village of Louth than all the Trocaz pigeons in Madeira – and therefore the world. An epidemic could hypothetically wipe out such a population quickly. For example, disease is believed to have killed off two native rodents on Christmas Island within a decade of the arrival of black rats and their contagions. The best safeguard against a similar fate is a robust, genetically diverse population. Still, there is no question that the species is a nuisance to many – and arguably an economic problem on Madeira. It is a conflict species: farmers have been known to illegally shoot and poison the pigeons. But Manuel J. Nogales Hidalgo, a reseacher with the Spanish National Research Council, said the government’s decision to cull the pigeons was “difficult to understand” given that usually endemic island species are suffering from far too few individuals – rarely too many. In some ways, the plight of the Trocaz pigeon is a microcosm for our global wildlife crisis. Around the world, wildlife populations have plunged by approximately 58 percent in just the last forty years, according to WWF and the Zoological Society of London, which are tracking 3,700 vertebrate species worldwide. As the human population has grown – seven billion plus – the world’s other life-forms have less and less habitat in which to make their homes and fewer resources to keep them alive. And whenever any of these non-human species – whether it is wolves, bears, elephants, rabbits, lions, spiders, snakes, leopards, deer, crows, coyotes, or Trocaz pigeons – dare to bother us in our space it rarely ends well for them. Sure, we’re fine with wild species – but only so long as they stay where they belong: in national parks and other protected areas (about 14 percent of land and 3 percent of the oceans). The human species is evolutionary covetous for the most part, unwilling to share, unwilling to live and let live, unwilling to sacrifice even just a little for another species’ well-being. Our lawns are manicured into grassy deserts, our lakes stocked with the fish we want to catch, our oceans blanketed by nets and lines, even our national parks are invaded by oil, gas, mining, and logging industries. It’s difficult enough for humans to share with other humans – let alone other animals. Still, as the Earth undergoes a potential mass extinction, it remains to be seen whether we humans are capable of viewing the natural world a little differently. Are we able to see our earth as something no longer limitless and no longer abundant, as something that is being displaced and wrung out? Something that’s maybe even worth sacrificing a little for? We don’t see any Trocaz pigeons on my hike through the laurisilva. But one afternoon I find them with my binoculars cooing on the sea cliffs. Large and heavy-set, the flashing stripes on their neck gives them an unexpected beauty. And I realize: this is the only place on our planet where one can do this - watch the light glint off a Trocaz pigeon’s silver feathers. Chilling out in the noon sun, the birds look as inoffensive as any life form could be – but then again they aren’t eating my garden. As I watch the pairs, I find myself trying to solve the puzzle: how do we keep the people happy and the pigeons alive? Should farmers be asked to give up on some of their crops? Should pigeons be moved out of agricultural areas? Should we just keep shooting? My mind wanders: why not stop the culling? But will farmers simply retaliate with illegal shooting and poisoning? Why not sell wildlife-friendly cabbage at a premium? Maybe the Maderian hipsters will love it – but most would still buy the cheap stuff. Or why not pay farmers for every lost cabbage? Why not ask tourists to donate to the ‘save the pigeons’ fund? Hey, we could rewild the island of Porto Santo with Trocaz pigeons – then we’d have an insurance population! I soon realise I don’t have an easy answer. But that’s the luxury of being a journalist: I don’t need one. I just need to tell the story and hope someone cleverer figures it out.
Valle S.,Manchester Metropolitan University |
Barros N.,Portuguese Society for the Study of Birds |
Ramirez I.,BirdLife International |
Wanless R.M.,Seabird Division |
Wanless R.M.,University of Cape Town
Ostrich | Year: 2016
The Tinhosas islands, in São Tomé e Príncipe, host the most important seabird breeding colony in the Gulf of Guinea, but information on its conservation status was hitherto unpublished or anecdotal, the last assessment having been performed in 1997. A two-day expedition to the Tinhosas islands was undertaken to estimate the status of breeding seabirds in 2013. Four of the five seabird species known to breed in São Tomé e Príncipe, namely Brown Booby Sula leucogaster, Sooty Tern Onychoprion fuscatus, Brown Noddy Anous stolidus and Black Noddy Anous minutus, occur on the Tinhosas. A decrease of 80% in Brown Booby numbers, possibly due to occasional exploitation, and a 30% increase in Sooty Tern and Black Noddy numbers, were found compared to 1997 data although survey methods differed. Breeding of Brown Noddy and Madeiran Storm-petrel Hydrobates castro remains unconfirmed. Our estimates confirmed that BirdLife International Important Bird and Biodiversity Area criteria are met for at least one species, the Sooty Tern. The islands are not legally protected, nonetheless, apart from moderate levels of disturbance by fishermen who land on Tinhosa Grande, no alien species were seen, and no immediate threats to the Tinhosas colony were detected. Multiple visits within and between years are recommended, to census breeders, monitor threats and establish breeding phenologies. © 2016 NISC (Pty) Ltd
Hervias S.,Portuguese Society for the Study of Birds |
Hervias S.,University of Murcia |
Hervias S.,Island Ecology and Evolution Research Group |
Henriques A.,Portuguese Society for the Study of Birds |
And 9 more authors.
Biological Invasions | Year: 2013
The most common invasive mammals-mice, rats, and cats-have been introduced to islands around the world, where they continue to negatively affect native biodiversity. The eradication of those invasive mammals has had positive effects on many species of seabirds. However, the removal of one invasive mammal species may result in abundance changes of other species due to trophic and competitive interactions among species. Understanding the overall impact of several invasive species is a key challenge when evaluating the possible effects of eradication programmes. Here we assess the influence of the three most common invasive mammals on nest survival of Cory's shearwater (Calonectris diomedea). We monitored six breeding colonies over 3 years and measured the activity of mice, rats and cats to examine the influence of invasive mammals on nest survival. We found that nest survival showed a similar temporal trend in all years, with lowest weekly survival probabilities shortly after chicks hatched. Cats were identified as major predators of chicks, but no measure of colony-specific cat activity was able to adequately explain variation in shearwater nest survival. Nest survival was on average 0. 38 (95 % confidence interval 0. 20-0. 53) and varied among colonies as well as over time. We found a small positive influence of rats on nest survival, which may indicate that the presence of small rodents as alternative prey may reduce cat predation of chicks. Our findings suggest that the eradication of rodents alone may exacerbate the adverse effects of cats on shearwater nest survival. © 2012 Springer Science+Business Media B.V.
Ceia R.S.,Portuguese Society for the Study of Birds |
Sampaio H.L.,Portuguese Society for the Study of Birds |
Parejo S.H.,Portuguese Society for the Study of Birds |
Heleno R.H.,CSIC - Mediterranean Institute for Advanced Studies |
And 3 more authors.
Biological Invasions | Year: 2010
The invasive Clethra arborea has a dual-role in the diet of the Azores bullfinch, a critically endangered bird species endemic to the island of São Miguel (Azores, Portugal). This is a crucial winter food resource but it lowers the availability of native laurel forest species that compose most of the bird's diet throughout the year. The removal of this and other invasive alien species is part of current laurel forest habitat restoration programmes, disregarding the impact on the Azores bullfinch population. In order to evaluate the first responses of the Azores bullfinch to habitat restoration, we studied bird diet, foraging behaviour, food availability and habitat occupancy in managed (without C. arborea) and control areas. Significant increases in the availability of native food resources in managed areas were noticeable in the diet, particularly the intake of Ilex perado ssp. azorica and Prunus lusitanica ssp. azorica flower buds. In most of the studied months birds heavily used and foraged in managed over control areas. The one exception was in December, when a resource-gap occurred in managed areas, which may be overcome in the short-term due to re-establishment of native plants following removal of invasive aliens. © 2010 Springer Science+Business Media B.V.
Hervias S.,University of Murcia |
Hervias S.,CSIC - Institute of Natural Products and Agrobiology |
Ceia F.R.,University of Coimbra |
Pipa T.,Portuguese Society for the Study of Birds |
And 3 more authors.
Zoology | Year: 2014
This study assessed the impact of introduced black rats (Rattus rattus) on Cory's shearwater (Calonectris diomedea borealis) in a multi-invaded insular ecosystem where rats are mesopredators. We hypothesized that black rats should have little impact on Cory's shearwaters in the presence of cats as superpredators. Stomach contents and stable isotope analysis (SIA) in tissues of black rats were analyzed to assess the trophic ecology and the importance of Cory's shearwater in their diet. We also studied the isotopic signature in tissues of house mouse (Mus domesticus) to confirm previous data showing no predation of this species on Cory's shearwaters. For both rodent species, temporal variation in diet composition in response to the availability of seabird prey was evaluated, and short- and long-term consistency in diet was tested using different tissues from the same individual. For black rats a Bayesian isotope mixing model (SIAR) was applied to determine the relative contribution of each prey to the individual diet. SIA of mouse tissues varied between the Cory's shearwater breeding and non-breeding periods. However, no significant differences were found in diet and SIA for black rats. In contrast, individuals of both species showed a strong consistency in diet which apparently benefited their body condition index. Although black rats supplement their diet with Cory's shearwater eggs and chicks (8.3% in stomach contents and 10.6% in the SIAR model), their current impact on the Cory's shearwater population appears to be small, probably due to several factors including the small size of the rat population and a high level of rat predation by cats. © 2014 Elsevier GmbH.