Spoonbills choose path of most resistance

Spoonbills that breed in the Netherlands prefer to migrate in autumn to areas with the poorest chances of survival. Two thirds of the birds go to West Africa, a third stay in Europe. The birds that migrate to Africa have a life expectation of about four years; the minority who stay in Europe live on average a year longer. Groningen biologist Tamar Lok and spoonbill expert Otto Overdijk from the Spoonbill Working Group told us all about it on Sunday 18 September, on the VARA Radio 1 programme Vroege Vogels (Early Birds). The results of their research will be published in the October issue of the scientific journal Animal Behaviour.

Between 1992 and 2010, nearly 6000 spoonbills were made individually identifiable for the research using a combination of coloured rings. This meant that they could be followed year by year on their migration routes. Of the ringed birds, 1256 were observed during the winter along the coasts of France, Spain, Portugal or West Africa. The researchers used the observations to derive an average migration behaviour and life history.

Mystery

‘It’s still a mystery why the spoonbills have a slight preference for areas with poorer chances of survival’, says University of Groningen PhD student Tamar Lok. ‘Their first winter much more than a third of the birds stay in Europe – 52% in Mauritania and Senegal as opposed to 48% in Europe. In the second year there appears to be a group that changes its mind about flying 2000 kilometres or less within Europe and decides to fly the full 4000 to 5000 kilometres to West Africa.’

Climate

Choosing the path of most resistance might be because the strongest birds have already occupied the best places in Europe, forcing the slightly weaker birds to fly on. It could also be that global warming has led to a gradual improvement in wintering grounds in Europe but that the spoonbills have not yet had the chance to adapt to the new situation.

Future

The researchers are positive about the future of the spoonbill in the Netherlands. Lok: ‘It looks like things are going the right way for the spoonbill in the Netherlands. The birds that stay in Europe generally have a life expectation that is more or less a year longer than those who go to Africa. If that trend continues, we might see fewer and fewer spoonbills crossing the Sahara and deciding to winter closer by.’

Note for the press

The research will be published in October in Animal Behaviour. The online version of the journal is already accessible: http://www.sciencedirect.com.
The Vroege Vogels show was broadcast on Sunday 18 September from 8-10 a.m. on Radio 1.
For more information:
- Vroege Vogels newsroom, tel. 035-671 19 11
- Tamar Lok, via the University Communication Office, phone +50363 4444