We provide detailed breeding parameters for the population of monk parakeets, Myiopsitta monachus, in Barcelona, Spain, based on data collected for 651 nests over five breeding seasons. This invasive population has a high reproductive capacity compared to the native range: fledging success was double, the percentage of pairs attempting second broods three times higher, and 55% of one-year old birds bred compared to almost zero in South America.

Most parakeets, parrots, and cockatoos are difficult to mark because of their strong beaks and ability to manipulate items with their feet. We developed a marking method that consists of a numbered tag hung on a neck collar. We used this method to successfully monitor Monk Parakeets (Myiopsitta monachus) and Ring‐necked Parakeets (Psittacula krameri) in Barcelona, Spain, from 2003 to 2009. We marked 881 Monk Parakeets and 88 Ring‐necked Parakeets with collars. Fifteen tags placed on adult Monk Parakeets in 2003 (N= 57) lasted until 2008 and nine until 2009. Three of 12 Ring‐necked Parakeets marked in 2003 were resighted in 2008. We estimated that 4.5% of Monk Parakeets and 5.8% of Ring‐necked Parakeets lost their tags, with median intervals between attachment and tag loss of 347 and 370 d, respectively. Behavioral observations revealed no differences in the time budgets of marked and unmarked Monk Parakeets. In addition, the mass of marked Monk Parakeets did not change between successive recaptures. These results suggest that neck collars had no adverse effects on the birds. Neck collars may also be a suitable marking method for other psittacines, with stronger, more durable components likely needed for larger species.

Invasive species threaten biodiversity all around the world and for this reason, identifying the causes and mitigating their effects is a priority in conservation biology. One of the most important factors when dealing with invasive species is dispersal, because the distribution of dispersal distances among members of a population can greatly affect the rate of spread of these invasive populations. Long distance dispersal events have a disproportionately large influence on dispersal kernel estimations, but because of restricted spatial sampling scales they are difficult to detect. Here we use an extensive database of 3,114 monk parakeets ringed in Barcelona city since 2002 as part of an extensive control program across Catalonia where 3,460 birds have been captured since 2013. Our aim was to describe these long–distance movements of monk parakeets. We recorded dispersal distances of over 10 km for a total of eight individuals. Long–distance dispersions were in all directions and both males and females were involved. While some individuals moved in their first year, others delayed dispersal several years. Given that long–distance dispersal events can have a large influence on the rate of range expansion of invasive species this information can be of great utility when modeling the dispersal and spread of the species.

The coping style of an individual in relation to potentially dangerous situations has been suggested to be inherited in a polygenic fashion, being SERT one of the candidate genes. In this paper, we assessed in free-living great tits Parus major the association between SNP290 in the SERT promoter and three standard fear-related behaviors, namely the response of the birds to a black and white flag fixed to the top of the nest-box, distress calling rate of the birds in the hand once captured and the hissing call of incubating females when approached by a predator. We found a strong association between SNP290 polymorphism and the three risk-taking behaviors, with birds with genotype CT entering faster to the nest box with the flag and displaying more distress calls and less hissing calls. CT birds could therefore be described as more proactive than CC individuals. These results also suggest that hissing behavior should be regarded as a fear-induced shy behavior, and confirm that SERT has an important function in relation to risk aversion behaviors and coping style.

Behavioural flexibility may play a relevant role during invasion of a new habitat. A typical example of behavioural flexibility favouring invasion success refers to changes in foraging behaviour. Here we provide data on changes in the foraging strategies of monk parakeets Myiopsitta monachus over a period of 17 years (2001–2017) in Barcelona city. During this time, consumption of food on the ground increased by more than 25 % and the consumption of anthropogenic food increased by 8 %. Detailed information about the food consumed is provided. Feeding on the ground and consumption of low plants allow parakeets to reach not only anthropogenic food but also crops, thereby increasing the risk of crop damage as the invasion evolves. Early detection of damage to crops is crucial in order to prevent further harm, and makes the precautionary principle highly relevant.