In the middle of the Atlantic, some small islets located northwest of Africa serve as shelter for the Eleonora's Falcon (Falco eleonorae) or aleta in the Canary Islands. Carried by the trade winds, only in the Chinijo Archipelago, composed of Alegranza, Montaña Clara, Roque del Este and Roque del Oeste, can this species of falcon be observed during its migratory journey through the African continent.
As a result of the presence of this species in the four eastern islets, Laura Esther Gangoso, Doctor in Conservation from the Complutense University of Madrid, has spent 18 years investigating the behavior of this type of bird of prey in the Canary Islands that breeds in the Chinijo Archipelago. This species only spends three months a year in Alegranza, then begins its journey through several African countries until it reaches Madagascar, where it hibernates.
"The Canary Islands is not in itself a migratory route for these birds, but they only arrive here if they are diverted by the action of the wind itself," explains the expert. The wind is also responsible for feeding these 300 pairs of falcons that nest in the Canary Islands islets. "The wind is the engine or the thread that unites the falcons with the Canary Islands, if there is no wind there are no falcons here."
"The wind and the Eleonora's Falcon are not conceived separately," explains expert Laura Esther Gangoso.
The roadmap that has helped determine where this type of falcon spends its time comes from the ringing work of the specimens. This has helped scientists to locate their journey around the continent. After leaving the Canary Islands and entering through the Saharan border, it reaches the Sahel countries and heads to southeastern Africa towards Madagascar, a journey it makes back at the end of winter.
The Eleonora's Falcon chooses these islets for the small birds that the trade winds drag to the Canary Islands and that serve as food. In addition, they are located in particular in the Chinijo Archipelago due to its proximity to Africa and being uninhabited and small islands where they can perceive the entry of these birds. "These islets are the first points of land that these diverted birds find. They have a perfect location," says the professor. In addition, "they have a funnel factor" that facilitates the hunting of food, she adds.
This research team has been studying their movements for years, where they go to hunt, their migration, where they spend the winter, their diet and their relationships with changes in the climate.
How climate change affects
Among the field work carried out for more than a decade and a half in Alegranza, Montaña Clara and the roques tries to explain how the imminent climate change affects the behaviors of this species. "Climate change is in turn changing the behavior of the trade winds. We say that this type of falcon is a sentinel of the climate, of those changes that we can measure and that we all witness," says the expert in Conservation.
For the scientist, changes in the climate globally also affect small populations such as the Eleonora's falcon as it passes through the Canary Islands. For example, it affects the prey it feeds on. "If in Europe there are very dry and hot years, it affects the populations of these little birds in Europe, they do worse. There are many things that are chained. If spring starts earlier, everything is brought forward, a series of imbalances occur and it affects the populations of these birds, changing their migration dates," she justifies.
Changes in routine interfere with the survival of this and other species. "The falcons are fully synchronized to reproduce at the precise moment when the autumn immigration of these little birds to Africa begins," she points out.
The lack of food means that, on occasions, the Eleonora's falcons end up feeding on other species of seabirds that nest in the Chinijo Archipelago, although they are not really their normal food. Gangoso explains that this is not the case of the shearwaters, "which are too large and cannot be prey for a falcon, but other seabirds that are smaller can." She also adds that, "the breeding season of seabirds coincides with that of the falcon and the latter are beginning to take advantage and feed on these birds."
"The relationship with seabirds is taking on enormous importance in the growth of falcon populations, but it is interesting to see how this change affects seabirds," she specifies.
This research that has been extended for 18 years in time reflects that the growth of the falcon population "is stable, and in slight increase, even." However, when emphasizing other details, such as the number of chicks that they manage to get ahead in the breeding season "fluctuates a lot from one year to another." It is for this reason that this group persists year after year in continuing to collect data on this bird of prey during its stay in the Canary Islands. "There have been terrifying years where that productivity value has been very low.
The Eleonora's Falcon nests on the slopes of the mountains, with its back to the wind and in rocky areas sheltered from the sun to be able to escape the heat. Like any story of perseverance, the research work of Laura Esther Gangoso in the Chinijo Archipelago has been supported by different institutions over the years. The project began with the Doñana Biological Station-CSIC. After that, the University of Amsterdam and now the Complutense University of Madrid. It has also been financed with many different projects (regional, national and European), and for many years they have also received support from the Cabildo de Lanzarote.
The complete work can be read on the website about the research.
