The social character of geese or corvids was well known and studied by scientists. These large birds tend to create stable bonds over long periods of time. However, it had not been observed in small birds, such as the lúgano (Carduelis spinus). A study published in the Bird Study reveals that this species tends to travel in groups for several years and over long distances.
So far, researchers from the Barcelona Museum of Natural Sciences, which is leading the work, had discovered that female captive lúganos prefer to mate with known males. But it remained to be shown that in nature these birds live together for periods of time long enough to interact and get to know each other.
"In this work we show how the lúgano can maintain stable group relationships for periods of several years, moving together at distances of more than 1,000 km", highlights Juan Carlos Senar, lead author of the study and scientist at the museum.
The team of researchers used the records of the European Union for Bird Ringing (EURING) - the European institution in charge of bird ringing and monitoring - to examine the data recorded from 42,707 lúganos between 1907 and 2011. To act more precisely, the experts they limited the study to birds that traveled more than 50 km from their banding site, a figure that exceeds the maximum distance these birds usually travel in a single day (10–40 km).
The results showed that lúganos can stay together in the same group for up to four years and can travel distances of up to 1,300 km with other individuals. Regarding the type of group, the records revealed that they could be both same-sex and mixed.
“The important thing is that several groups of individuals that traveled together hundreds of kilometers were detected, and that they were both a male and a female (possible partners) and copies of the same sex, which implies that the associations were not only couples, but they could also be groups of friends with a social bond ”, highlights Senar.
Flying to the same place is not just a coincidence
Until now, some studies had shown a marked sociability in small birds such as the American lúgano (Carduelis pinus) and the sicerín linnet (Acanthis flammea), but the studies were carried out within the same winter, and therefore the distances of movement were relatively small and lasted only a few months.
Senar and his team wanted to replicate these results in the lúgano, using displacements throughout the biological period and throughout the entire life of an individual. "An additional importance of having carried out the work with lúganos is that this species, unlike the goldfinches (Carduelis carduelis) or the greenfinches (Carduelis chloris), is nomadic, so that each year its individuals move to a different place" , indicates the scientist.
Therefore, “if two individuals are recaptured together hundreds of kilometers from where they were captured for the first time, it is not because the two are going to winter at the same site independently and they simply coincide, but that they have necessarily had to move together ”, Explains the researcher.
The study also reveals that individuals prefer to mate with others who are familiar to them. This can be an important local adaptation mechanism. For this, the requirement is that the individuals interact for long periods of time, something that, as the work shows, these small birds also fulfill.
Juan Carlos Senar et al. "Do Siskins have friends? An analysis of movements of Siskins in groups based on EURING recoveries ”Bird Study 62 (4): 566-568. October 12, 2015 DOI: 10.1080 / 00063657.2015.1089836