Allow me to reintroduce myself: My name is Tessa, I’m 24 years old and I’m a Master student from the Wageningen University in the Netherlands, where I study Forest and Nature Conservation. You may remember my article from the June’s Newsletter, where I wrote about the Iberian azure-winged magpie (Cyanopica cooki). At the time my research was still ongoing, and I was out in the field almost everyday to look for these beautiful birds. Now, almost half a year later, my written thesis has been completed and I believe to have unravelled the success of the Azure-winged Magpie! But before I tell you about all my findings, here is a short recap:
The Iberian azure-winged magpie has been found to have increased in numbers in southern Portugal in the past decades, but it is unknown what makes this species so successful. Considering that many bird species are currently declining, it is interesting to know what can make a species successful in our current time and age. Moreover, it is rumoured that the magpies steal and eat the chicks of other passerine birds. This means that the success of the Iberian azure-winged magpie could become a double-edged sword that threatens the existence of other birds, and thus, research is needed! In order to unravel the factors behind its success and to further study these rumours, I did a fieldwork study together with Esra (18), another student from the Netherlands. Together we cycled line transects in the field. I also did a small behavioural study on the azure-winged magpie in the area near Cruzinha. During the line transects we specifically looked at the urban : green ratio within each section of the line transect, but we also recorded a handful of other variables. The reason we looked at the urban : green ratio is that, in the first weeks of fieldwork, Esra and I went to all kinds of natural areas, located far up in the hills, in the forests or in the middle of nowhere, yet we barely encountered any magpies no matter where we went. However, whenever we made our way back home and would cross towns, suddenly we’d see magpies everywhere! This gave me an idea… perhaps the magpies aren’t out there in the wild anymore, but there where the people are?
Now that you’re all up to date, let’s get to what we found! First of all, we found that Iberian azure-winged magpies highly prefer areas that have an intermediate to high (50% – 75%) cover of green area, which we named Category 3 and 4, respectively. Here, the remaining area is considered urban, which includes households, buildings and hardened terrain. These areas contained significantly more magpies than areas with a low green area cover (Category 1; 0% green and Category 2; 25% green), but also significantly more than areas that are completely green (Category 5; 100% green)! This is quite surprising, as it has not yet been mentioned in literature that Iberian azure-winged magpies now occur rather close to human settlements. As seen in these results, the magpies prefer areas with a mix of nature and human settlements over areas that are completely green or completely urbanized. This is precisely what I expected after the observations made in the early fieldwork stage, and changing my method seems to have been a good call after all!
During the behavioural study it also became clear that magpies tend to flock to human settlements in order to look for food, be it our own food or the feed of the animals. I regularly observed magpies stealing the food from the dogs at Cruzinha, and I also received footage of magpies stealing food from cats, dogs and even geese. Another behaviour I observed regularly was that of magpies flying into a garden and, after a few minutes, flying back to a natural area where they’d clean their beaks. After this, they would often return to the garden again, from where they repeated the cycle. It is likely that the magpies were foraging in the gardens and returned to a safe natural area after feeding to clean their beaks. Moreover, I observed many magpies using fences, poles and powerlines as a look-out post from which they could search for food. In this manner, they can use infrastructure to improve their foraging strategies. These observations show that the magpies have learned how to take advantage from human settlements while also still enjoying the safety and resources of natural areas. This would also explain why the magpies nowadays prefer areas with low to intermediate levels of urbanization. Looking at other species from the Corvidae family shows that many species of magpies, crows and raven have learned how to use human settlements to their advantage, and some species even have higher reproduction rates when breeding near human settlements. It is likely that the Iberian azure-winged magpie is one of the latest species in the Corvidae family to have learned how to profit from humans.
Now one question remains, which is whether the Iberian azure-winged magpie predates on the eggs and chicks of other passerine birds. I did not observe this behaviour during my stay, however this does not necessarily mean that the magpies do not predate on other birds. It likely has to do with my behavioural study being too small (about 20 hours of observations) to observe this possibly scarce behaviour. Moreover, I may also have conducted the study too early in the season (end of March – beginning of May), when there was not yet an abundance of eggs and chicks for the magpies to steal. As such, further research may be needed to discover whether the magpies do indeed regularly predate on eggs and chicks and, if so, what the impact of this behaviour is on the populations of bird species that are predated on by the magpies.
Overall, I conclude that the Iberian azure-winged magpie has learned to profit from human settlements, which improved its foraging strategy and has likely aided to an increased reproductive success. As such, the magpie population has been able to successfully expand over the past decades. However, it is still unknown whether the species predates on the eggs and chicks of other passerine birds, and how large the impact of this behaviour would be. As it is likely that the Iberian azure-winged magpie population will continue to increase, some might be happy knowing that this colourful magpie species will continue to roam the skies of southern-Portugal, while others might fear for their pets’ dinner. I, for one, look forward to seeing these beautiful, cheeky birds again one day!