Mammal introductions on oceanic islands across a human disturbance gradient: conservation implications for the Azores islands.

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Impact of introduced nest predators on insular endemic birds : the case of the Azores Woodpigeon (Columba palumbus azorica)

Publication . Lamelas-López, Lucas; Fontaine, Rémi; Borges, Paulo A. V.; Gonçalves, David

Nest predation is the main cause of reproductive failure in many bird species. Identification of predators is crucial to understand and interpret the factors that affect nest predation. Although nest predation is a natural top-down regulator of bird populations, its effect is usually more dramatic when introduced predators are involved, particularly in oceanic islands. In the Azores archipelago, the endemic Azores Woodpigeon (Columba palumbus azorica) is believed to be under high predation pressure. We used motion-triggered cameras to monitor nests of the Azores Woodpigeon on two islands of the archipelago (Pico and Terceira) in order to identify nest predators, quantify their impact on this bird and better understand the determinants of predation rates. We sampled 56 nests, during 569 camera trap days, obtaining around 125,000 photographic records. Two introduced predators were identified, black rat (on both islands) and feral cat (only on Terceira), both depredating eggs and chicks. Breeding success, calculated using the Mayfield method, was estimated at 19% on Pico and only 9% on Terceira. Overall, predation was the main cause of breeding failure. General linear models showed that predation rates are positively correlated to fruit availability and negatively correlated to elevation, human population density and adult Woodpigeon attendance at the nest. Edge distance, nest height or cover of trees did not affect predation. Camera traps also provided additional and useful information on predator behaviour when approaching a nest and on daily activity patterns of both adult Woodpigeon and nest predators.

2020-08Journal article

Restricted access

Sampling of Azores seabirds with camera-traps - Year 2019

Publication . Lamelas-López, Lucas; Borges, Paulo A. V.

The Azores holds the largest population of Cory´s shearwater Calonectris borealis (Cory, 1881) in the world. One of the major threats of this species in the Azores is the predation by invasive mammals, which were introduced from European colonization of the islands. The present publication provides a data set from a camera-trapping survey performed in colonies of Cory’s shearwater. The sampling was conducted between 8 April and 23 October of 2019, covering the entire breeding season, in three colonies of the Terceira Island (Azores). A total of 32 nests were sampled using motion-triggered cameras. This publication aims to provide information about the ecological patterns of the Cory Shearwater, and to identify potential nest predators. This publication includes a total of 6972 records across 15 species (9 species of birds, 5 of mammals and 1 of reptiles), which 5414 records are of Cory’s shearwater, 478 of potential mammal predators and 1080 of another vertebrate species. Information about biology of the species is also provided, as species circadian behaviour and habitat description.

2023-02Dataset

Open access

Factors influencing the relative abundance of invasive predators and omnivores on islands

Publication . Lamelas-López, Lucas; Santos, Maria J.

Invasive alien species (IAS) are the major cause of native species extinctions on islands worldwide. To mitigate or eliminate IAS impacts, eradication is often the best alternative. However, IAS removal may result in cascading effects, through increase in prey abundance, mesopredator release, or competitor release. Our objective is to determine which ecological processes may influence the relative abundance of invasive carnivores and rodents on an insular system. We find that feral cat and mustelids relative abundance was strongly related by prey abundance, and for the feral cat, abundance was also controlled by habitat; these results suggest that bottom-up control through environmental filtering could be the mechanism explaining predator abundance. For rodents, we find that the abundance of the black rat was mostly controlled by the abundance of Norway rat and house mice, and food availability; the Norway rat by the abundance of black rat, a house mice and of mustelid predators; and house mouse by the other rodents and food availability. These results suggest that several mechanisms could be concurrently controlling abundance of these species; competition and predation for Norway rat, and competition and bottom-up control by environmental filtering for the other two rodents. While different factors explain the abundance of invasive species within the same functional group, food resource availability is, in general, the main controller of abundance of invasive rodents and carnivores in the Azores. Therefore, IAS management actions in these islands should focus on limiting the access to food resources and shelter, mainly near to human populations.

2021-05Journal article

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Applying camera traps to detect and monitor introduced mammals on oceanic islands

Publication . Lamelas-López, Lucas; Salgado, Iván

The introduction of mammal predators has been a major cause of species extinctions on oceanic islands. Eradication is only possible or cost-effective at early stages of invasion, before introduced species become abundant and widespread. Although prevention, early detection and rapid response are the best management strategies, most oceanic islands lack systems for detecting, responding to and monitoring introduced species. Wildlife managers require reliable information on introduced species to guide, assess and adjust management actions. Thus, a large-scale and long-term monitoring programme is needed to evaluate the management of introduced species and the protection of native wildlife. Here, we evaluate camera trapping as a survey technique for detecting and monitoring introduced small and medium-sized terrestrial mammals on an oceanic island, Terceira (Azores). Producing an inventory of introduced mammals on this island required a sampling effort of 465 camera-trap days and cost EUR 2,133. We estimated abundance and population trends by using photographic capture rates as a population index. We also used presence/absence data from camera-trap surveys to calculate detection probability, estimated occupancy rate and the sampling effort needed to determine species absence. Although camera trapping requires large initial funding, this is offset by the relatively low effort for fieldwork. Our findings demonstrate that camera trapping is an efficient survey technique for detecting and monitoring introduced species on oceanic islands. We conclude by proposing guidelines for designing monitoring programmes for introduced species.

2021-03Journal article

Open access

Surveying Cory Shearwater colonies with camera traps and identifying potential invasive nest predators

Publication . Lamelas-López, Lucas; Borges, P.A.V.

Background The Azores holds the largest population of Cory's shearwater Calonectris borealis (Cory, 1881) (Aves, Procellariiformes, Procellariidae) in the world. One of the major threats of this species in the Azores is the predation by invasive mammals, which were introduced during European colonisation of the islands. The present study provides a dataset from a camera-trapping survey performed in colonies of Cory’s shearwater. The sampling was conducted between 7 April and 23 October 2019, covering the entire breeding season, in three colonies of the Terceira Island (Azores). A total of 32 nests were sampled using motion-triggered cameras. The aims of this study are to provide information about the ecological patterns of the Cory shearwater and to identify potential nest predators. New information Our results include a total of 6972 records of 15 species (nine species of birds, five of mammals and one reptile), of which 5414 records are of Cory’s shearwater, 478 of potential mammal predators and 1080 of another vertebrate species. Information about the biology of the species is also provided, as species circadian behaviour and habitat description.

2023-04-03Journal article

Open access