Waiting for the bullfinches. Field work is never easy.
Those that we are waiting for are Barbados bullfinches. When you sit at a terrace in Barbados, it's almost guaranteed that you will share your table with bullfinches. Of all the street smarts (see Figure 4 and sup. 1 and 2 movies) they use to forage, the bullfinch steal sugar packets and they are able to open them to extract the sugar (see movie below). Our multiple terrace visits allowed us to discover that there was independent appearance of this innovation (and not just social transmission).
Barbados bullfinch opening a sugar packet. (from: http://link.springer.com/article/10.1007%2Fs10071-013-0612-4)
But what about bullfinches that live in the country side, where there are no sugar packets lying around? Would rural bullfinches be capable of accomplishing such feats, if they had the opportunity to do so? My supervisor Louis Lefebvre and we decided to test this idea by comparing the behavior of rural and urban bullfinches.
The goal was to capture bullfinches in places with different degrees of urbanization, from highly rural to highly urbanized (see map below). The northeastern zone of Barbados is one of the few areas that are relatively untouched by human presence, so rural sites are concentrated in this area of the island. In contrast, the west coast is very populated, partly because of the very high tourist activity. Going out in the wild (and in the human wilderness), in uncharted territories to capture birds represents some challenges. We often had to chase out monkeys, mongooses, giant bumblebees or even horses that were too interested by our mist nets but we were also chased out ourselves by angry farmers who though we were poaching on their land. We also needed some street smarts to elaborate the logistics with very limited means and we even had to manufacture some specialized equipment. In any case, this adventure was a lot of fun and it is my best field work experience to date.
Our 8 capture sites. Red indicators designate rural sites and yellow, urban sites.
Once we captured our birds – and many more other wonderful bird species that happened to fly in the nets – we brought the bullfinches in the “lab” at the Bellairs research institute. The “lab” was in fact 4 walls and a roof. For the rest, we had to figure out how to make it look like an aviary. Again, a lot a streets smarts was needed there.
Me, proud of my artisanal mist net installation on a rural site.
And that is when, finally, the real science began. Our first behavioral task aimed at measuring the birds’ boldness, by recording how long it takes for the birds to come at the feeder after a human disturbance. Expectedly, the urban birds were bolder, probably because they are more habituated to the human presence. We also measured neophobia, the fear of novelty. We used the same protocol as for boldness but a novel object was placed beside the feeder. Surprisingly, the urban birds were more neophobic than the birds from rural areas. While we don’t know the real reason for this, this could be explained by the fact that birds living in urbanized areas learn to fear the novel situations because of their potential danger, whereas rural birds live in very predictable environments and never learn to fear weird situations. For more details on the temperament results, see the original article.
Our most striking result is the finding that urban bullfinches are more street smart than country birds, as reported by IFLScience. In fact, birds captured in urbanized areas were faster at solving two different problem-solving tasks. Those problem-solving tasks (see video made by National Geographic, below) were specifically designed to mimic technical foraging innovations in the wild, like the sugar packets opening. Having a better ability to solve problems in a city could mean life or death.
We have also measured immunocompetence in birds from both environments. To do so, we injected PHA into the wing of bullfinches and 24 hours later we measured the intensity of the reaction. This measurement is a proxy for the strength of the immune system. We first hypothesized that the immunity would be reduced in animals that have better cognitive abilities, since it is costly to maintain both systems at the same time. We imagined that the immunity would be a good candidate for a trade off trait against problem-solving ability. We were wrong. It appears that the urban birds’ immunocompetence is much higher than in rural birds. It seems that in this case, the urban birds have it all, although I find this hard to believe. Another possibility is that the city birds live well, but they die faster than country birds. In fact, in a study involving great tits, telomeres were found to be shorter in urban birds compared to rural birds. In any case, if I were a bird, I would probably be an urban bullfinch.
The article « The Town Bird and the Country Bird: problem-solving and immunocompetence vary with urbanization. » was published in Behavioral Ecology, 2016; 27(2):637. http://beheco.oxfordjournals.org/content/27/2/637