Diet assessments as a tool to control invasive species: comparison between Monk and Rose-ringed parakeets with stable isotopes

Abstract

Food is a main limiting factor for most populations. As a consequence, knowledge about the diet of invasive alien species determines the design of control measures. The Monk and Rose-ringed parakeets are two typical species of successful invasive parrots that are highly appreciated by people. Although some observations suggest that Monk parakeets rely on a higher percentage of anthropogenic food than Rose-ringed parakeets, no detailed quantitative data is available. The aim of this study was to compare the diet of the two parakeets using stable isotope analysis (SIA). We performed SIA of carbon and nitrogen in feathers collected in Barcelona, Spain. We also measured isotopic ratios for potential food sources. We reconstructed the diet of parakeets using Bayesian mixing models. The two species differed in the isotopic signatures of their feathers for both δ13C and δ15N. Diet reconstruction showed that Monk parakeets feed mainly on anthropogenic food (41.7%), herbaceous plants (26.9%) and leaves/seeds (22.2%), while Rose-ringed parakeets feed mainly on flowers/fruits (44.1%), anthropogenic food provided in the trap located at the museum (32.4%) and leaves/seeds (23.1%). The more detailed information we can obtain from the diet of these species is useful to develop more effective control measures for their populations. The Monk parakeet may be more susceptible to control through education local residents, given the greater use of anthropogenic food in this species compared to Rose-ringed parakeet. Our conclusions also indicate that SIA is a powerful tool in providing crucial information about the diet and informing measures to control invasive species.

Aspects of the feeding ecology of introduced Rose-ringed Parakeets Psittacula krameri in the urban landscape mosaic of Durban, KwaZulu-Natal Province, South Africa

“…syringa Melia azedarach, Natal fig Ficus natalensis, and pawpaw Carica papaya fruit/ flower throughout the year. Similar studies also found that parakeets are mainly frugivores and granivores (Clergeau and Vergnes 2011;Klug et al 2019;Shiels and Kalodimos 2019;Borray-Escalante et al 2020). We also observed the parakeets feeding on insects such as carpenter ants throughout the year as a supplementary dietary item.…”

“…Humans have been the only contributing factor in the introduction of Rose-ringed Parakeets from their native to non-native ranges through the exotic pet trade (Symes 2014;Jackson et al 2015). Rose-ringed Parakeets show plasticity in feeding behaviour and are generalist-opportunistic feeders consuming a variety of foods including insects and plant components such as flowers, seeds, twigs, fruits, and leaves (Eason et al 2009;Ahmad et al 2011;Clergeau and Vergnes 2011;Fraticelli 2014;Symes 2014;Tella et al 2015;Borray-Escalante et al 2020). Although the feeding ecology of Rose-ringed Parakeets has been reported in other countries (Ahmad et al 2012;Fraticelli 2014;Shiels et al 2018), relatively little has been documented in South Africa (Thabethe et al 2015;Ivanova and Symes 2019).…”

Cryptosporidium spp. and Giardia spp. in Free-Ranging Introduced Monk Parakeets from Santiago, Chile

“…More notably, Monk Parakeets are the only species among the order Psittaciformes that does not rely on preexisting cavities to nest, since they are able to build their own communal nests [ 7 , 12 , 42 ]. Furthermore, they feed on a flexible diet, allowing them to exploit a wide variety of fruits and seeds [ 13 ]. Additionally, their gregarious behavior leads them to engage in communal parenting, increasing their possibilities to avoid predatory attacks [ 6 , 7 , 12 ].…”

“…Monk Parakeets’ invasive success can be associated with the unique behavioral and ecological characteristics of the species [ 10 , 11 ]. Their great reproductive capacity and ability to prosper in novel environments can be attributed to, among other things, their reproductive, nesting, and dietary habits [ 6 , 7 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

Leaf bathing in ring-necked parakeets Psittacula krameri

“…The interesting point here, however, is that we have been monitoring parakeets in Barcelona for the last twenty years, and although we have seen monk parakeets bathing in pools of water many times, we have never observed ring-necked parakeets performing this behaviour. Ring-necked parakeets rarely come down to the ground in our area, not even to eat (Borray-Escalante et al, 2020). We have sometimes observed them drinking in puddles, but never bathing.…”