Endemism… Excuse me?
I mentioned it in my introduction; there are about ten endemic bird species in Réunion. But what does endemism mean? Simply put, a species is endemic when it occurs in a limited geographical area. Isolation is one of the key factors that can lead to species having a restricted distribution. When a particular population becomes isolated from the source population, that new population adapts to the new environment. In this way, new species may emerge over time. Not surprisingly, islands are often hotspots of endemism. Reunion is no exception. Numerous endemic plants, insects, birds, and even mammals occur on the island. There used to be many more. Endemic species are particularly vulnerable to environmental changes because their limited distribution means they cannot simply ‘flee’ from danger. The colonization of Reunion in the 18th century had a far-reaching impact on the island's biodiversity. For example, did you know that giant tortoises used to live here?
Reunion is located relatively close to Madagascar. The nearest neighbouring island is Mauritius at about 180 kilometres. Source: WikiCommons - TUBS
The last of the mohikans…
By 2003, only seven pairs of the Reunion cuckooshrike remained, which was the signal to take far-reaching management measures to save the bird from extinction. How did it come to this? Let's go back in time for a brief history lesson. About two million years ago, Réunion rose out of the Indian Ocean courtesy of a massive volcanic eruption. Réunion sits on a volcanic hotspot, which causes intense volcanic activity. Neighbouring Mauritius is much older than Reunion and used to lie on top of the hotspot eight million years ago. The volcanic activity on the island caused animals to go extinct even before humans colonized the island. Genetic research has also shown that the cuckooshrike was already on the verge of extinction some 5,000 years ago. Unsurprisingly, this period coincided with a major volcanic eruption.
Even today, volcanic activity can still be found in Réunion. The Piton de la Fournaise volcano is one of the most active in the world. Its last eruption was in 2023.
In 1642, the first people arrived on hitherto uninhabited Reunion. These were prisoners deported from Madagascar by the French. In 1663, the French East India Company colonized the island. From that point onward, the population rose massively, driven in large part by the massive importation of enslaved people, which is a story I keep for another time. The story's moral is that colonization caused an extinction wave. For instance, nearly all species associated with the savannah on the island's eastern side disappeared, including the Réunion giant tortoise.
At first, the Reunion cuckooshrike seemed to stand firm. In 1885, François P.L. Pollen, a Dutch naturalist and explorer, noted that the cuckooshrike was abundant and found at 800 meters altitude and higher. The human population continued to rise. Ecosystems came under increasing pressure. Today, some 73% of the original vegetation is gone, 30 out of 45 vertebrate species are extinct, and more than 900,000 people live on an island with an overall population density similar to Belgium. If you know that much of the island consists of uninhabitable, rugged mountains and volcanoes, you know there is a massive pressure on the coastal area. Hence, the cuckooshirke retreated to tropical forests between 1,300 and 1,800 metres altitude. Nowedays, the species still occurs in a patch of about 12 square kilometers. Compared to the seven breeding pairs of 2003, things are improving. Today, about 125 to 180 adult birds roam around in the wild.
Here we overlook the island's east coast. Heavily built-up in stark contrast to the rugged interior. Factory smoke spreads. Cars show where the highways are.
On rats, cats, and other scum
How did the Réunion cuckooshrike recover from just seven breeding pairs in 2003 to 125–180 adult birds today? Most effort goes into exterminating black rats, the ultimate alien species. Virtually wherever humans have colonized islands, black rats have caused the islands to become a few species poorer. Special trapping devices with rat poison are strategically placed throughout the area to eliminate them. However, this does not come without any risk. The rat poison must be carefully managed to ensure it does not harm the island's only bird of prey, the endangered Réunion harrier.
In addition to rats, domestic cats are another culprit. While rats primarily feed on eggs, cats are capable of preying on adult birds too. Cats are trapped and spayed/neutered, among other things.
A third problem case is the red-whiskered bulbul. This beautiful invasive species of bird is becoming more and more widespread. Once confined to the coastal regions, this species is now steadily expanding into the inland tropical forests.
In conclusion, human activity introduced these invasive species to Réunion, pushing the cuckooshrike and other native wildlife toward the brink of extinction. Yet, with ongoing conservation efforts, there is hope for recovery.
This red-whiskered bulbul is the newest enemy of the tuit-tuit. This bird is colonising the native forests and outcompetes the original fauna.
Orange-white, red metal
This gibberish is the ring code of the individual I could observe during my holiday. Each bird in the population is assigned a unique color ring code, allowing for individual tracking. These ring codes revealed that cuckooshrikes start a new life at (on average) 360 meters from their parental nest. This limited urge to explore new territory makes the bird enormously vulnerable. Expansion of the current range will be a long-term work. The rugged landscape of the island doesn't help either. If we want the cuckooshrike to return to other parts of the island where it historically occurred, artificial translocation is the only solution.
Hundred-metre-deep valleys criss-cross the island. Even for birds, these pose considerable barriers. Without human help, tuit-tuit cannot pass these obstacles.
In total, it took me two attempts to see a cuckooshrike. The first time I hiked through the breeding area was when I started the big crossing of the island (GRR1) with Amber. We didn't have much time, as we had to cover quite some distance each day. We could hear a few callings anyway, which gave me hope for later! Three weeks later, I returned alone to pull out all the stops to see one.
It is early and the full moon is still high up the sky. Still, noise can be heard from the forests. I can hear some tuit-tuit, réunion bulbuls, réunion stonechats and réunion olive white-eyes.
The alarm goes off at 4:30 a.m., and the sun will rise within a good hour and a half. I will have to walk for over an hour before the spot where I heard a male call three weeks earlier. It rained all day yesterday, and the path is slippery. I begin my journey by walking through a forest of cryptomeria, a non-native tree species widely planted for timber production. The only problem is that wood rots quickly in humid climates, limiting the usefulness of cryptomeria. Large tracts of cloud forest disappeared in turn for cryptomeria plantages. Luckily, the Roche Ecrite Nature Reserve still has plenty of natural vegetation. In particular, I am impressed by the tree ferns. Where the forest opens up, and heather bushes emerge, the tuit-tuit area begins. Soon, I hear several birds. One of them sounds suspiciously close. I can’t leave the path, but a bit further down, I find a good spot to look out, but no sign of a tuit-tuit. Luckily, a tec-tec (Réunion stonechat) poses perfectly for a photo, helping me pass the time while I wait for the tuit-tuit.
The réunion stonechat, locally called tec-tec, is distinguished from our stonechats by its distinctive eyebrow stripe.
A little later, I hear the tuit-tuit again, close by. On the thicket-covered slope in front of me, I suddenly see a bird flying through the thicket. Could that be the bird I am searching for? I lose the bird again. Fortunately, a little later, I find the bird in the bushes. Yes, It is a male tuit-tuit! What a magnificent bird! He comes closer and closer, and suddenly, I see that it is color-ringed, making the observation even more interesting! Orange and white mark its left leg, and red and metal on the right leg. I lose the bird again, but mission accomplished!
There he is! A male réunion cuckooshrike, it even starts singing right in front of me.
So, what do we know about OrangeWhiteRedMetal - for the sake of the story, I'll call him Alfred for a moment. Thanks to people from the Life program and SEOR (Société d'Études Ornithologiques de La Réunion) who focuses on tuit-tuit conservation, I know almost everything about the bird. Alfred was born in December 2017. In other words, he is seven years old, which is a decent age for a Reunion cuckooshirkes. Alfred is a pretty loyal guy. He had a relationship with a first female that lasted for two years. After this, he has been a couple with the same female till today, and they successfully provided offspring during several seasons. This year is another success too! Researchers spotted the couple again breeding eggs in the same tree as before.
Let's keep our fingers crossed for a new generation of spout-tufts and a hopeful future for this critically endangered species!
The tuit-tuit's preferred habitat. Tropical semi-open forest and well-developed scrub. An indescribably magical place!
More information:
- Salmona, J., Dawson, D.A., Fouillot, D. et al. The utility of existing passerine microsatellite markers for genetic studies in endangered species: as demonstrated for a critically endemic forest bird endemic to Réunion Island, the Réunion cuckooshrike (Coracina newtoni). Conservation Genet Resour 2 (Suppl 1), 361-364 (2010). https://doi.org/10.1007/s12686-010-9254-x An article about the genetic research on this bird species.
- Nicolas Le Roux, Evaluation des risques génétiques dans la population d'échenilleur de la Réunion (Lagage newtoni): Implications pour conservations - Masters thesis about the genetic background of the species
- https://lifecapdom.org/videos-40/article/tuit-tuit?lang=fr more information about the Life project