Releasing captive-bred animals into the wild where they belong is a magical process to be involved with. For those caring for the birds on a day-to-day basis and in some cases weighing them as naked, blind, defenseless newborns, to see them spread their beautiful, colorful wings and fly free outside of a cage is an indescribable feeling. When you boil it down, it seems deceptively simple: breed from unreleasable pairs, raise chicks, release into the wild. Thirty years ago, that may well have been it, but since the 90’s there has been an ever-increasing demand for understanding how and why some reintroductions are successes and others are failures: reintroduction science. This is something we whole-heartedly agree with, from an individual welfare point of view and as a donor funded NGO, we want to be sure that we are using your money as effectively as possible, having the most impact for the birds.
We use knowledge we have gained, experience other projects carrying out Macaw releases, as well as insights from other species and not just birds. It is not an easy science. We are working in challenging, wild environments over which we have no control. So, every small piece of information we can gather, from anywhere, is extremely valuable. To really understand how we can improve our releases we have to be able to track individuals after they have been released. Only by doing this will we be able to know if our work pre-release has any positive or negative influence on survival, successful breeding, and ultimately establishment of a self-sustaining population. We currently introduce young birds to wild foods, carry out flight training in a large pre-release aviary, and do predator-aversion training. The big question is does any of this work, is it necessary? Parrots are clever, maybe it’s not?
The issue with Macaws, as well as other parrots, is it is difficult to track individuals. For most birds, coloured leg bands, a unique color combination for each individual, helps a field team monitor individuals. The part of the leg that these bands go on is the tarsus, in parrots this is proportionally much smaller than in most other birds. Coupling this with the parrots fluffy trousers and penchant for sitting down, hiding the colour bands, means this is not a viable way to track individuals. Radio-tracking is possible, but the terrain around Punta Islita with lots of ridges and valleys means it is extremely difficult to do efficiently. Another option is GPS collars, but a number of projects have used these to varying success. Macaws are also great at destroying their very expensive GPS backpacks.
For our last release at Punta Islita we decided to use a novel method of tail clipping, cutting unique patterns into some of the tail feathers of the birds to enable us to identify them post release. We coupled this with marking their beaks with color coded numbers, so if one method failed the other could also be used. We knew this was not a long-term solution, but we hoped it would enable us to track individuals for at least a month, ideally three.
We also carried out a pilot study on personality, social interaction, and bonding within the release flock. This involved monitoring who was socializing with who, seeing who were the bold individuals and who took a back seat at feeding time. We decided to do this because there is an increasing amount of research that might influence post-release survival. Think of it as picking a football team. You pick players based on their characteristics, ideally a good spread of skills who bond well together. The chances of picking a random group of players and them having the right set of skills is very low. Research suggests that might be the case with release groups (Bremner-Harrison, Prodohl and Elwood, 2004; Bremner-Harrison, Cypher and Harrison, 2013; Bamber, Shuttleworth and Hayward, 2020; Franks et al., 2020).
One month after the release, we could still identify our release flock, at three it was no longer reliable. At one month there was a mix of the two types of marks, so the backup theory worked. Well, that was apart from one individual, Light Green. She could not be identified in the birds who were using the supplementary food or seen in the area surrounding the release site. She could have flown off, a common issue with any monitoring is that emigration looks just like death at a site level. Either way, our small pilot study suggested that Light Green had the lowest socialization score, so if she flew off or died it could have been because she didn’t have strong enough bonds with the rest of the flock. She couldn’t take advantage of all the benefits of being in a group, especially in those vital weeks and months post-release.
We need more data to be able to say this is something we can use to assess suitability of release in the future. But, promising that all the work that went into the study suggested it should be continued. We are collaborating on a number of potentially exciting technologies that could drastically increase our ability to monitor released and wild birds in the future. Right now, we are working to increase the effectiveness of our current techniques, so we can monitor our upcoming release flock for longer post-release. The longer we can monitor them the more information we can gather, the better we can be at returning Macaws to all the skies they once graced.
If you haven’t already, be sure to read Part 1 of this blog to learn more about why we breed for release! You can also be part of our upcoming release here!
Tom Lewis
PhD student and board member
Bamber, J.A., Shuttleworth, C.M. and Hayward, M.W. (2020) ‘Do Differing Levels of Boldness Influence the Success of Translocation? A Pilot Study on Red Squirrels (Sciurus vulgaris)’, Animals, 10(10), p. 1748. doi:10.3390/ani10101748.
Bremner-Harrison, S., Cypher, B.L. and Harrison, S.W.R. (2013) ‘An investigation into the effect of individual personality on reintroduction success, examples from three North American fox species: swift fox, California Channel Island fox and San Joaquin kit fox’, in Soorae, P.S. (ed.). Abu Dhabi, UAE: IUCN/SSC Re-introduction Specialist Group and Environment Agency-Abu Dhabi, pp. 152–158. Available at: http://irep.ntu.ac.uk/id/eprint/20008/ (Accessed: 1 May 2022).
Bremner-Harrison, S., Prodohl, P.A. and Elwood, R.W. (2004) ‘Behavioural trait assessment as a release criterion: boldness predicts early death in a reintroduction programme of captive-bred swift fox (Vulpes velox)’, Animal Conservation forum, 7(3), pp. 313–320. doi:10.1017/S1367943004001490.