Department of Physics, Chemistry and Biology (IFM)

20 birds were captured in the four different capture sites, ten in the urban area and ten in the rural area between September and November 2016. Only adults were kept, juveniles were freed as results in neophobia and problem solving abilities may be influenced by age (Greenberg and Mettke-hofmann, 2001; Griffin and Guez, 2014). No discrimination was made between sexes, neither an attempt to equalize them due to the difficulty to differentiate them. Captures were performed in the early morning (07:00-11:00) or late afternoon (16:00-20:00), hours inside their activity peak (Ralph, 1993; personal observations). A mist net that was located at strategic places the birds used to pass (Ralph, 1993) . When a bird tried to fly through the net, it crashed and stayed entangled in it. An expert in bird manipulation untangled the bird from the net, without causing any harm to the animal, placed it in a fabric bag and transported it immediately to the captivity facilities at the Universidad Mayor de San Andres (UMSA), La Paz, where the environmental conditions were similar to the ones of the capture sites. The birds were kept in captivity four days, the fourth day they were freed at the same location where they were caught. The enclosures were cleaned and disinfected before the entrance of a new bird.

The birds were housed at individual enclosures (170 cm height x 136 cm width x 460 cm length) that were visually but not acoustically isolated from each other in an outdoor aviary . It was considered that an outdoor aviary would replicate their natural habitat conditions (noises, soil ground, climate conditions and other birds around) and therefore the responses would be less confounded, and more similar to the natural ones in the wild. However, the birds were given two days of adaptation before the behavioural tests started, following the methodology of Audet et al. (2015). During these days, the birds were fed ad libitum with birdseed, fresh fruits (apple, grapes and oranges) and bread. Fresh food was refilled in the mornings at 09:00. Water was always available. The birds after the two days’ adaptation were feeding properly and no bird showed obvious signs of stress.

The behavioural tests were carried out on day three and four at 09:00, inside their activity hours (Ralph, 1993). On the day preceding the behavioural tests the birds were food deprived overnight for 15 hours, from 18:00 until the end of the behavioural test (around 09:30) to increase motivation when confronted to the test. After the tests the birds were again fed ad libitum until the next food deprivation. When confronted to the tests it was assumed that all birds where under an identical starving situation. However, it was impossible to ensure this as it was unknown their exact last feed before the deprivation or if they had different metabolic rates.