The conservation status of the Galapagos MartinProgne modesta: Assessment of historical records and results of recent surveys

Abstract

Summary The endemic Galapagos Martin Progne modesta is a rare species. Population sizes in the past are unknown, but the few reports available suggest that it has become rarer in some sites. To obtain a better understanding of its population status, a simultaneous survey was conducted in 2017 around the coastline of 14 islands and 23 islets resulting in sightings of only 26 individuals. A simultaneous survey on Sierra Negra volcano on Isabela Island added five more individuals. However, observations from early expeditions and expeditions since 2015 have shown that the volcanoes of Isabela Island are important feeding areas and probable breeding areas for the Galapagos Martin, but these were largely excluded from the survey in 2017 due to logistical reasons. Historical and recent nesting sites include Tagus Cove on Isabela Island and Daphne Major Island. During our 2017 count, three possible new nesting sites were discovered: Daphne Minor, Santiago and a small crater on Punta Cristóbal on southwestern Isabela Island. From 2015 to 2018, 15 nests were also observed on the cliff in Tagus Cove. Two accessible nests were collected and revealed the first records of Philornis downsi in Galapagos Martin nests. The impact of parasitism by P. downsi is unknown but potentially severe. Given the lack of general knowledge about the biology of this species and its apparent low population sizes, further studies are urgently needed.

Effect of an introduced parasite in natural and anthropogenic habitats on the breeding success of the endemic little vermilion flycatcher Pyrocephalus nanus in the Galápagos

“…First, the parasitic fly P. downsi is now common on many Islands of the Galápagos, and its hematophagous larvae are obligate parasites of 21 Galápagos land bird species (Fessl et al , Anchundia and Fessl , Coloma et al , S. Knutie, pers. obs.).…”

Reproductive system and activity patterns of Philornis downsi (Diptera: Muscidae)

“…It is believed to have been accidentally introduced before the 1960s from mainland South America, with the first records of larvae reported in nests of Darwin's finches in the 1990s (Couri 1999, Fessl et al 2001, 2018, Causton et al 2006). At present, it has invaded 15 of the 17 largest islands of the archipelago and is found in a wide range of hosts, attacking approximately 20 species of Passeriformes, 2 species of Cuculiformes and 1 species of Columbiformes, causing serious alterations in the populations of some of these birds (Fessl et al 2018, Causton et al 2019, Anchundia and Fessl 2020, Coloma et al 2020). Some species that are critically endangered include the medium tree finch ( Camarhynchus pauper ) (O'Connor et al 2010) and the mangrove finch ( Camarhynchus heliobates ) (Cunninghame et al 2015).…”

Persistence of the invasive bird-parasitic fly Philornis downsi over the host interbreeding period in the Galapagos Islands

“…In Galapagos it parasitizes many species of land birds, feeding on nestlings and causing high rates of mortality 20 – 22 . Philornis downsi has persisted in Galapagos since at least the 1960s and is known to attack 21 bird species (including 11 of 17 species of Darwin’s finches) from most habitats on at least 15 islands 21 , 23 , 24 . This is despite the fact that almost all known hosts in Galapagos exhibit a distinct breeding season during the hot period (January through May), which is associated with sporadic rain showers and an increase in insect food for developing nestlings 25 , 26 .…”