Project tasks included fieldwork, both observational and experimental, as well as laboratory and computational work. I worked with a natural population in the field, and hence many environmental hazards that escape the control of researchers may potentially affect the progress of the work. In our case, the breeding season in the spring of 2016 was unusually bad for the birds. Heavy rainfall during the nestling period and cold temperatures, along with an unusual strong predation by a Stone marten (Martes foina), that appeared photographed in our camera traps, drop the fledging success to only 10% of nests. As a consequence, I intensified data collection the next season in the spring of 2017 but this produced a delay in the timing for the laboratory results and analyses. Even so, the project arrived to interesting conclusions, with some of them also being subjected to revision with new laboratory results on genetic relatedness and increased sample size.
We already know from previous work that helping is beneficial to helped chicks (who increase survival and condition) and hence to parents (who gain reproductive success). But our results in this project have revealed an amazing finding: parents' survival is reduced when they receive help. We reached at this result by using capture-recapture data for individually marked birds. The result is paradoxical but it makes all sense when it is placed into the context of our previous knowledge on this species. We had already published that parents that count on helpers increase their effort to feed the chicks. This should entail survival costs. The interesting thing is that parents decide to increase their breeding effort when the opportunities to succeed in the current season are high because of the presence of helpers, since despite this decision may reduce survival, it increases lifetime reproductive success and hence it is favoured by selection. But why do this effect only happen in this species? Perhaps the highly unpredictable conditions that occur in these Mediterranean habitats, those that also affected our research in 2016, are responsible for the benefit balance between present and future, so that taking advance of a realized current good opportunity prevails against preserving for an uncertain future.
But our main question to tackle was why helpers help to unrelated birds. We have analysed two types of reciprocity, direct and indirect. By direct reciprocity we expect helped individuals to repay to their helpers individually. Indirect reciprocity, by contrast, is based on the idea that helping individuals may receive more help from any other birds in the group. To study direct reciprocity we considered the opportunities for paying back, i.e. whether the previously helped individual was available when the helper has laid its eggs and would need help. We found that although there were many opportunities for direct reciprocity it only happened very rarely, so we conclude that this should not be the main mechanism to maintain helping. Then we looked at indirect reciprocity, i.e. the help received by any members in the group. And yes, the results show that individuals that helped more received more help. Now we are deepen into the analysis of which individuals in particular give help to those that previously helped others, the possible role of spatial proximity between nests and the relationships within the social network.
