New study reveals nesting secrets of Golden Eagle
New tracking project reveals crucial information for the conservation of Mexico’s national bird, including five new breeding territories near a quarry in Sonora. The majestic predator loves places that are hard to reach.
Careful footsteps shuffle forwards in the night. It’s a few hours before sunrise and an intense rainstorm threatens. A flash of lightning freezes the wincing face of a conservationist, who hopes his creaking backpack is not making too much noise. His colleague stumbles, so he quickly shines a red light to make sure she doesn’t collide with a prickly cactus.
They are in the remote Sonoran desert of north-west Mexico, on a special mission for a special bird. “Fear coupled with an adrenaline rush. Because if you make a mistake, they can maim you.” This is how Javier Cruz, Field Technician from Pronatura Noroeste (BirdLife in Mexico), describes fitting a radio transmitter to a Golden Eagle Aquila chrysaetos. The team has scaled cliffs and camped wild in mountains to locate the Golden Eagle nests, as part of a joint project between Pronatura Noroeste and the global cement and aggregates company, CEMEX.
The project is centred on CEMEX’s nearby Cerrito Blanco quarry, set deep in the biodiverse Sonoran desert, where the partnership – which began in 2012 – has undertaken field surveys for birds, mammals, plants, reptiles and amphibians and assessed the potential impacts of human activities in the area. As part of this ‘Biodiversity Action Plan’ to ensure good management of this sensitive area, Pronatura Noroeste and CEMEX studied the abundance and distribution of Golden Eagles and organised a national workshop to find out more, but this process unearthed important information for the team: the population is poorly understood nationally, let alone in the area around the quarry.
Despite a stable population trend when averaged out globally, the Golden Eagle is threatened in Mexico having been extirpated from most of its original range. The study found that over-grazing of native flora by cattle ranching is a factor, as it likely inhibits the abundance of prey availability for Golden Eagle and other top predators in the area like Mountain Lion.
One of the tagged Eagles © Pronatura Noroeste
Golden Eagle is a priority species for conservation nationally. “They are Mexico's national bird”: stresses Martha Laura Argüelles Corral, from CEMEX Corporate Social Responsibility at their Yaqui plant. “We are proud to participate in a Biodiversity Action Plan to support Golden Eagles, their conservation is a concern”.
With surveys revealing at least two pairs of Golden Eagle nesting not far from main quarrying operations, Pronatura Noroeste’s project with CEMEX provided a unique opportunity to find out more – a chance not to be missed. The team set out to tag juvenile birds with radio-transmitters to better understand their range and dispersal, working with the Mexican Environment Agency (CONANP). “It was a unique experience,” says Javier Cruz. “And we never thought that it would yield so much information, from the daily movements, where they perch, where they fly to and above all, where they sleep.”
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The transmitter-backed eagles have produced maps of the birds’ movements and now a picture is emerging of their post-natal dispersal. According to Francelia Torres, Field Technician, Pronatura Noroeste: “Now we know that their distribution can often include many municipalities, including an individual crossing the US border. As well as places very difficult to access, what surprised us the most was that Golden Eagles frequent places often with very little human disturbance.”
The project is showing that this region is very important for the conservation of Golden Eagle, and giving a real insight into their lives. After a year of having fitted transmitters, five new breeding territories have been confirmed in Sonora in 2016. The project’s workshop also enabled the training of a skilled local Golden Eagle conservation team. Miguel Cruz, Project Coordinator, Pronatura Noroeste is excited for what they can continue to find: “The team continues to strengthen, in a region where it was unknown that they could be nesting.”
One very special bird
Slap-bang in the middle of the Mexican flag, clutching a snake in its talon, perched on top of a prickly pear cactus, is a Golden Eagle. With an impressive wingspan of over two metres, the Águila Real (Royal Eagle in Spanish) is a great choice for a national emblem. But as a top predator, it is also a good indicator for the health of the Mexican environment, as it relies on abundant prey.
This is why the next phases of the project include restoration of Sonoran grassland habitat, especially focussing on a tree-like cactus that reaches over 20 metres: the Saguaro. This cactus is recognised as a keystone species in the ecosystem, meaning it supports a wide variety of other life; particularly bats and birds, which use them to nest. Other current plans include engaging landowners since changes in cattle ranching are needed to benefit the whole ecosystem, including Golden Eagle.
Pronatura and CEMEX surveying the landscape © Pronatura Noroeste
Nearby, CEMEX wants to ensure they have a positive impact around the quarry. “The alliance between CEMEX Mexico and Pronatura Noroeste has been very valuable,” says Martha. “We look forward to continuing to work together to contribute to the biodiversity management of Cerrito Blanco”.
Pronatura Noroeste have also begun outreach work to prevent the persecution of Golden Eagles. But surprisingly for the most part, despite their size, they are not well known by local villagers. “This is a very cautious bird,” according to Francelia. “They are even overlooked by the locals”.
The team hopes to restore local Sonoran attachment to the Golden Eagle, as their project uncovers more conservation secrets. Javier knows what this feels like, already: “After fitting the radio transmitter, freeing the eagle I felt the most immense satisfaction and sense of peace.”
A quick photo before releasing the tagged bird © Pronatura Noroeste