New Blue Crane research answers age-old
questions, and raises concerns
Blue Cranes keep surprising us, as we continue to learn more about South Africa’s enigmatic national bird.
And no one knows this better than Christie Craig, Researcher at the Endangered Wildlife Trust and Extension Officer for the Overberg Crane Group.
Christie has spent the past five years studying Blue Cranes, their movements and the threats to them in the Overberg and the Swartland. This forms part of her PhD into understanding how viable the Blue Crane population is into the future. While Christie is in the process of completing her doctorate, she’s already shared some of her incredible results with the Overberg Crane Group.
Spreading their wings
Between 2016 and 2021, Christie and her EWT colleagues fitted 30 trackers on Blue Cranes across the Overberg and the Swartland. Most of the cranes were post-fledgling cranes, caught over winter using foot noose traps at feeding troughs.
Christie has shared the movements of three non-breeding Overberg birds. These three are not resident here, and move across regions. Take a look at the distances these cranes travelled:
- Crane 1 moved east, but his tracker failed close to George.
- Crane 514 moved along the southern coast of South Africa – all the way into the Eastern Cape, including a couple of stopovers in the Addo Elephant National Park. Unfortunately, this individual became entangled in a fence close to Humansdorp and died.
- Crane 512 may also come from the Overberg, but this individual has headed up along the West Coast and inland past Worcester – all the way up to the Western Cape boundary. It spent quite some time on the West Coast, and even made a few stops just north of Cape Town, before returning to the Overberg. As far as Christie knows, Crane 512 is still alive and well.
The exception rather than the rule
She says that despite these three showing their ability to travel massive distances, most cranes fitted with trackers are more sedentary. She shared the results of the home ranges of two Blue Cranes in the Overberg.
- BCRA02 is a breeding bird in the Overberg making use of the agriculture land in the Rûens, especially around Klipdale.
- OV502 is a non-breeding bird that remains in the floater flock in the Agulhas area, moving around some of the agricultural and natural areas between the De Mond Nature Reserve and the Agulhas National Park. Note this crane is mostly reliant on land in private ownership, and not on the formally protected areas.
(On the map to the right, the solid lines provide the home range estimates; and the dotted lines provide 95%
confidence intervals. Black lines are the total home range; blue lines are the winter home range and red lines the summer and breeding home range.)
Christie says, “My analysis shows that non-breeding birds have larger home ranges than breeding birds.”
Loyal to the end
Christie has also reaffirmed the loyalty that Blue Cranes have towards each other. She captured and put satellite trackers on two birds in the Swartland that turned out to be a breeding pair. She says, “There have always been questions about whether breeding pairs remain together throughout the year, or whether they go their separate ways. But during the study period, we came to see that that they stay together year-round.”
Some concerns flagged by the research
There are also some worrying results coming out of Christie’s research. There are increasing concerns about the breeding success rate in the Overberg and Swartland, which is considerably lower than the grassland and Karoo regions. Her research estimates a success rate of 0.81 fledglings per Blue Crane pair in the Overberg. It’s even lower in the Swartland, at 0.64 fledglings per pair. The Karoo came to 1.02 fledglings per pair and the grasslands 1.01.
Already her research has led to more studies to better understand nest failure, with the EWT supporting research into the impacts of climate change on birds that are incubating. These individuals need to lessen their thirst on hot summer days – but this time away makes their nest more vulnerable. This research is also looking at nest predation, especially by Pied Crows.
While Christie has already made a number of interesting discoveries, and answered many questions on Blue Crane behaviour, she’ll be sharing much more in the coming months, including information on powerline collisions and population trends.
Now we need your help
As the study has now concluded while Christie writes up her findings, the trackers have been turned off. It’s therefore vital for the project team to continue monitoring these birds without the use of technology. Therefore, if you come across a bird that has a satellite tracker with colour tags on its legs, please let Christie know. Email: firstname.lastname@example.org.
Christie’s study was funded by the Leiden Conservation Foundation and the Hall-Johnson Fellowship. The Endangered Wildlife Trust and the Overberg Crane Group work in partnership to protect Blue Cranes in the Overberg. The EWT and the International Crane Foundation work together in furthering conservation of cranes and their habitats throughout Africa. The EWT Western Cape project is supported by the Leiden Conservation Foundation and Eskom.
Images: Christy Craig