Conservation status of landbirds on Floreana: the smallest inhabited Galápagos Island

Abstract

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.

Population dynamics of an invasive bird parasite, Philornis downsi (Diptera: Muscidae), in the Galapagos Islands

“…Field studies and population viability analyses suggest that P . downsi has already played a major role in the decline of the two Critically Endangered island endemics, Medium Tree-finch and Mangrove Finch [44,45,46,47]. Even for more common species like the Medium Ground-finch, there are predictions of extinction within the next 100 years [48].…”

An inter-island comparison of Darwin’s finches reveals the impact of habitat, host phylogeny, and island on the gut microbiome

“…scandens ), the small tree finch ( Camarhynchus parvulus ), and the endemic, critically endangered medium tree finch ( C . pauper ) [21]. Within the Galapagos system, Floreana Island has the longest history of human settlement and, likely for this reason, the highest record of local extinction of land birds within the archipelago.…”

“…difficilis ) by ~1870 [22], the Floreana mockingbird ( Mimus trifasciatus ) by 1895 [23], the warbler finch ( Certhidea fusca ) by 2004 [24], the large tree finch ( C . psittacula ) genetically confirmed absent by 2010 [25], and most recently the vegetarian finch ( Platyspiza crassirostris ), which was not detected in surveys in 2015 [21]. Currently, the impact of the invasive parasitic fly, Philornis downsi , which was first discovered in Darwin’s finch nests in 1997 [26], is considered especially detrimental to the persistence of critically endangered species (reviewed in [27]).…”

Survival and extinction of breeding landbirds on San Cristóbal, a highly degraded island in the Galápagos

“…the area around El Junco was successfully restored with Miconia (Bush et al 2014). A small reforestation project with the endemic Scalesia pendunculata has started in a private reserve (San Cristóbal Biological Reserve Jatun Sacha), but only a large-scale restoration programme, similar to that planned in Santa Cruz (Wilkinson et al 2005) would be beneficial to landbirds (Dvorak et al 2012(Dvorak et al , 2017. In southern Isabela, where Scalesia forest has been destroyed (Mauchamp and Atkinson 2010), large areas are dominated by uniform stands of guava and pasture, which seem less suitable for many bird species, including the Little Vermilion Flycatchers (Charles Darwin Foundation, BF unpubl.…”