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Colonial birds often breed at high density, generating conflict among neighbours over the use of nest-building materials. However, in a few colonial species, breeders appear to cooperate in the construction of compound nests that contain multiple breeding chambers within a single nest structure. The relative contributions of individual birds and the balance between cooperation and conflict among close neighbours in such species have rarely been examined. In this study, we investigated evidence for cooperation and conflict in the building and maintenance of the nests of monk parakeets Myiospsitta monachus in an invasive population in which compound nests are frequent. First, we found that males invested more in nest construction than females and when more than one male occupied the same breeding chamber multiple males contributed to the same nest. Females, by contrast, invested more in nest defence than males. Second, we found that there was conflict among pairs over nest material, with kleptoparasitism of nesting material and defence against conspecifics evident. We conclude that nest-building in monk parakeets involves both cooperation and conflict. Breeders often tolerate the budding of nests, which are often built by relatives, but that pairs are also in conflict over the use of nest material., Colonial birds often breed at high density, generating conflict among neighbours over the use of nest-building materials. However, in a few colonial species, breeders appear to cooperate in the construction of compound nests that contain multiple breeding chambers within a single nest structure. The relative contributions of individual birds and the balance between cooperation and conflict among close neighbours in such species have rarely been examined. In this study, we investigated evidence for cooperation and conflict in the building and maintenance of the nests of monk parakeets Myiospsitta monachus in an invasive population in which compound nests are frequent. First, we found that males invested more in nest construction than females and when more than one male occupied the same breeding chamber multiple males contributed to the same nest. Females, by contrast, invested more in nest defence than males. Second, we found that there was conflict among pairs over nest material, with kleptoparasitism of nesting material and defence against conspecifics evident. We conclude that nest-building in monk parakeets involves both cooperation and conflict. Breeders often tolerate the budding of nests, which are often built by relatives, but that pairs are also in conflict over the use of nest material., Las aves coloniales suelen criar en comunidades con una alta densidad, lo que genera conflictos entre los vecinos por el uso de materiales para la construcción del nido. Sin embargo, en algunas especies coloniales, los individuos reproductores parecen cooperar en la construcción de nidos compuestos, que contienen múltiples cámaras de cría, pero mantienen una estructura de nido único. La contribución relativa de los individuos y el equilibrio entre la cooperación y el conflicto entre vecinos cercanos son aspectos muy poco estudiados en estas especies. En este estudio, analizamos los indicios de cooperación y conflicto en la construcción y el mantenimiento de los nidos de las cotorras argentinas, Myiopsitta monachus, en una población invasiva en la que los nidos compuestos son frecuentes. En primer lugar, observamos que los machos invirtieron más en la construcción del nido que las hembras y que cuando más de un macho ocupaba la misma cámara de cría, múltiples machos contribuían al mismo nido. En cambio, las hembras invirtieron más en la defensa del nido que los machos. En segundo lugar, constatamos que se generaban conflictos entre parejas por el material de nidificación y que se producían episodios de cleptoparasitismo de material de nidificación y de defensa en contra de ejemplares conespecíficos. Concluimos que la construcción de los nidos de las cotorras argentinas trae consigo cooperación y conflictos. Los reproductores suelen tolerar que se vayan construyendo nidos adosados al ya existente, a menudo por parientes, pero esas parejas también entran en conflicto por el uso del material de nidificación.

Nest material kleptoparasitism occurs when an individual steals material from another individual's nest. Here we document 69 observations of grey herons, Ardea cinerea, removing nest material from the nests of monk parakeets, Myiopsitta monachus. The observations coincided with the breeding season of grey herons in Barcelona. We observed the behaviour by multiple individuals, across two years, at multiple nests in four different monk parakeet nesting trees, suggesting that theft of nesting material by grey herons is prevalent in this population. The large nests of the monk parakeet may present a rich source of nesting material that is less costly to collect than gathering nest material elsewhere. Our observations add to the relatively limited number of reports of nest material kleptoparasitism in wild birds and especially between heterospecifics., Nest material kleptoparasitism occurs when an individual steals material from another individual's nest. Here we document 69 observations of grey herons, Ardea cinerea, removing nest material from the nests of monk parakeets, Myiopsitta monachus. The observations coincided with the breeding season of grey herons in Barcelona. We observed the behaviour by multiple individuals, across two years, at multiple nests in four different monk parakeet nesting trees, suggesting that theft of nesting material by grey herons is prevalent in this population. The large nests of the monk parakeet may present a rich source of nesting material that is less costly to collect than gathering nest material elsewhere. Our observations add to the relatively limited number of reports of nest material kleptoparasitism in wild birds and especially between heterospecifics., Nest material kleptoparasitism occurs when an individual steals material from another individual's nest. Here we document 69 observations of grey herons, Ardea cinerea, removing nest material from the nests of monk parakeets, Myiopsitta monachus. The observations coincided with the breeding season of grey herons in Barcelona. We observed the behaviour by multiple individuals, across two years, at multiple nests in four different monk parakeet nesting trees, suggesting that theft of nesting material by grey herons is prevalent in this population. The large nests of the monk parakeet may present a rich source of nesting material that is less costly to collect than gathering nest material elsewhere. Our observations add to the relatively limited number of reports of nest material kleptoparasitism in wild birds and especially between heterospecifics.

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 3,039 monk parakeets ringed in Barcelona city since 2002 with an extensive control program across Catalonia where 3,460 birds have been captured since 2013, with the aim of describing 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., 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 3,039 monk parakeets ringed in Barcelona city since 2002 with an extensive control program across Catalonia where 3,460 birds have been captured since 2013, with the aim of describing 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., Las especies invasivas amenazan la biodiversidad en todo el mundo y, por ello, en el ámbito de la biología de la conservación se considera prioritario determinar las causas y mitigar los efectos de este fenómeno. Uno de los factores más importantes en relación con las especies invasivas es la dispersión, ya que la distribución de las distancias de dispersión entre los miembros de una población puede incidir notablemente en la velocidad de propagación de estas especies invasivas. Los episodios de dispersión a larga distancia tienen una influencia desproporcionadamente alta en las estimaciones de la dispersión de densidad de kernel, pero resultan difíciles de detectar debido a que las escalas de muestreo son restringidas. En el presente artículo utilizamos una extensa base de datos de 3.114 ejemplares de cotorra argentina que han sido anillados en la ciudad de Barcelona desde el año 2002, junto con los datos de un amplio programa de control en toda Cataluña gracias al cual se han capturado 3.460 aves desde 2013, con la finalidad de describir estos desplazamientos a larga distancia de las cotorras argentinas. Ocho de los ejemplares recorrieron distancias de más de 10 kilómetros. La dispersión a larga distancia se produjo en todas direcciones y tanto en machos como en hembras. Algunos ejemplares se desplazaron en su primer año de vida, mientras que otros tardaron varios años en hacerlo. Habida cuenta de que los episodios de dispersión a larga distancia pueden tener una gran influencia en la velocidad de expansión de la distribución de las especies invasivas, esta información puede ser muy útil para elaborar modelos de la dispersión y la propagación de la especie.

Habitat selection has profound consequences for individual fitness, but how do animals decide where to settle? The natal habitat preference induction (NHPI) hypothesis proposes that individuals choose habitats that exhibit similar environmental cues to those experienced in early life. In this study, we first examined juvenile movements and dispersal and then tested the NHPI hypothesis in the monk parakeet, Myiopsitta monachus, an invasive species that nests primarily in pine or palm trees in our study site. Juveniles were observed ranging extensively, but we found no relationship between ranging distances prior to dispersal and subsequent natal dispersal behaviour. As predicted by NHPI, we found that dispersed individuals displayed a significant preference for nesting in their natal tree type in their first year, irrespective of tree availability. The probability of changing tree type was not influenced by individual dispersal distance, the proportion of the natal tree type available or natal tree type.We found that adult birds undertaking breeding dispersal also showed a preference for the same tree type they dispersed from when making nest site selections, demonstrating that preferences can be maintained by adults during breeding dispersal movements. Finally, conspecific breeding success did not differ between palm and pine tree nests, and so did not provide a useful source of public information regarding the suitability of the two nesting substrates. These results contribute to our understanding of the drivers of habitat selection in both adults and juveniles and have implications for our understanding of dispersal patterns and range expansion in this worldwide invasive species., Habitat selection has profound consequences for individual fitness, but how do animals decide where to settle? The natal habitat preference induction (NHPI) hypothesis proposes that individuals choose habitats that exhibit similar environmental cues to those experienced in early life. In this study, we first examined juvenile movements and dispersal and then tested the NHPI hypothesis in the monk parakeet, Myiopsitta monachus, an invasive species that nests primarily in pine or palm trees in our study site. Juveniles were observed ranging extensively, but we found no relationship between ranging distances prior to dispersal and subsequent natal dispersal behaviour. As predicted by NHPI, we found that dispersed individuals displayed a significant preference for nesting in their natal tree type in their first year, irrespective of tree availability. The probability of changing tree type was not influenced by individual dispersal distance, the proportion of the natal tree type available or natal tree type.We found that adult birds undertaking breeding dispersal also showed a preference for the same tree type they dispersed from when making nest site selections, demonstrating that preferences can be maintained by adults during breeding dispersal movements. Finally, conspecific breeding success did not differ between palm and pine tree nests, and so did not provide a useful source of public information regarding the suitability of the two nesting substrates. These results contribute to our understanding of the drivers of habitat selection in both adults and juveniles and have implications for our understanding of dispersal patterns and range expansion in this worldwide invasive species., Habitat selection has profound consequences for individual fitness, but how do animals decide where to settle? The natal habitat preference induction (NHPI) hypothesis proposes that individuals choose habitats that exhibit similar environmental cues to those experienced in early life. In this study, we first examined juvenile movements and dispersal and then tested the NHPI hypothesis in the monk parakeet, Myiopsitta monachus, an invasive species that nests primarily in pine or palm trees in our study site. Juveniles were observed ranging extensively, but we found no relationship between ranging distances prior to dispersal and subsequent natal dispersal behaviour. As predicted by NHPI, we found that dispersed individuals displayed a significant preference for nesting in their natal tree type in their first year, irrespective of tree availability. The probability of changing tree type was not influenced by individual dispersal distance, the proportion of the natal tree type available or natal tree type.We found that adult birds undertaking breeding dispersal also showed a preference for the same tree type they dispersed from when making nest site selections, demonstrating that preferences can be maintained by adults during breeding dispersal movements. Finally, conspecific breeding success did not differ between palm and pine tree nests, and so did not provide a useful source of public information regarding the suitability of the two nesting substrates. These results contribute to our understanding of the drivers of habitat selection in both adults and juveniles and have implications for our understanding of dispersal patterns and range expansion in this worldwide invasive species.