This study develops a mixed, systematic, low-cost methodology to define and map native vegetation and the spread of the most aggressive invasive species in islands biomes, focusing on the Galápagos National Park (GNP). Based on preliminary legends defined by experts, Landsat 8/OLI fusion imagery was used for object-oriented classification to obtain the vegetation map of this archipelago. This technique was later verified and validated using high-resolution images from unmanned aerial vehicles (UAVs, i.e., drones) and dedicated satellites, ground truthing, and visual confirmation around GNP coasts. This mixed methodology allowed mapping of nine native ecosystems, six invasive-dominated vegetation units, and two types of lavas. Around 53.63% of GNP is covered by native ecosystems and ∼2.2% is “canopy” dominated by invasive species to date. Native-dominated deciduous forest types cover ∼40.8% of the GNP and only ∼12.8% of the protected area is nowadays covered by humid and transitional type native ecosystems. Among humid native ecosystems, those distributed in the highlands only cover 4.8% and are highly threatened by invasive species, which are mostly distributed in these summit areas. Of the five islands (out of 18) recording invasive-dominated units, Isabela and Santa Cruz were the most infested. Cedrela odorata, Pennisetum purpureum, and Psidium guajava were the main invasive plants dominating the GNP canopy. Highly noxious Rubus niveus was the only invasive species dominating areas among the five infested islands. Methodology detailed here proved useful to provide accurate spatially-explicit islands vegetation data, potential for replication in time, and is expected to aid suitable management of highly endangered and unique biotas in this and other tropical island biomes.

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On Floreana, the smallest inhabited island in the Galápagos, populations of several species of birds have either been extirpated or, based on anecdotal evidence and small‐scale surveys, are declining. Our objective, therefore, was to conduct a comprehensive survey of landbirds encompassing the entire island during three breeding seasons (2014–2016). We conducted surveys at 59 points in 2014, 257 in 2015, and 295 in 2016. Each survey point was sampled once. We detected 12 species during our surveys. Galápagos Flycatchers, Yellow Warblers, Small and Medium ground‐finches, and Small Tree‐Finches were widely distributed over the entire island. Common Cactus‐Finches and Medium Tree‐Finches had more restricted distributions in the lower or higher parts of the island. Few Dark‐billed Cuckoos (Coccyzus melacoryphus), Paint‐billed Crakes (Neocrex erythrops), Galápagos Doves (Zenaida galapagoensis), and Galápagos Short‐eared Owls (Asio flammeus galapagoensis) were recorded. Small Ground‐Finches and Small Tree‐Finches were found at densities comparable to those on other Galápagos Islands, whereas densities of Galápagos Flycatchers and Yellow Warblers were higher on Floreana than on other islands. Endemic Medium Tree‐Finches were confined to an area of 24 km², mainly in the highlands, but were still widespread and common in their restricted habitat, with the number of territories estimated to be between 3900 and 4700. Of 22 originally occurring landbirds on Floreana, no fewer than 10 species have either been extirpated or are likely to have been extirpated since the arrival of the first human inhabitants. The combined effects of introduced mammals, large‐scale habitat destruction, and direct human persecution were responsible for the extirpation of six species during the 19th century. Three additional species have been extirpated since 1960, likely due to the introduction of the parasitic fly Philornis downsi, and this fly remains a major threat for the remaining bird species. Developing strategies for reducing the impact of these flies on the birds of the Galapagos Islands must be a high priority. In addition, habitat management and restoration, including the control of invasive plants and promotion of native tree species, will be critically important in conserving landbird populations on Floreana.

In the Galápagos Islands many endemic bird species, including the emblematic Darwin's finches, show significant declines in population size. The endemic little vermilion flycatcher Pyrocephalus nanus, classified as vulnerable with high extinction risk, is strongly declining and broods regularly fail. We investigated multiple causes for breeding failure by comparing breeding success, infestation intensity by the hematophagous larvae of the introduced parasitic fly Philornis downsi, predation, parental food provisioning rate and prey attack rates as indicators of food availability at three study sites differing in anthropogenic habitat alterations: Alcedo on Isabela Island with its pristine habitat remote from human settlements, El Cura, also on Isabela Island but dominated by farmland, and Mina Roja on Santa Cruz Island, a site highly altered by introduced invasive plant species, mainly the blackberry. To test for the causal role of parasitism, we reduced the number of P. downsi larvae in half the nests at each site on Isabela Island, and used the other nests as control. When infestation intensity was experimentally reduced, both breeding success and food provisioning rates increased significantly in El Cura, but not in Alcedo, where breeding success and food provisioning rates were overall higher and infestation intensity lower than in El Cura. In the very small population of the little vermilion flycatcher in Mina Roja most nests were abandoned during the incubation phase before nests were infested by P. downsi. Mammalian predation played a minor role in brood loss at all three study sites. Our experimental study demonstrates that the recently introduced parasitic fly significantly affects breeding success of an endangered endemic bird species, and suggests that the effects are modulated by natural levels of P. downsi infestation and habitat‐related rates of food provisioning. Conservation measures should include P. downsi control combined with creating and maintaining open foraging areas.