Large tree finch

About: Large tree finch is a research topic. Over the lifetime, 6 publications have been published within this topic receiving 269 citations. The topic is also known as: Shell & Large tree-finch.

Species Collapse via Hybridization in Darwin's Tree Finches

Abstract: Species hybridization can lead to fitness costs, species collapse, and novel evolutionary trajectories in changing environments. Hybridization is predicted to be more common when environmental conditions change rapidly. Here, we test patterns of hybridization in three sympatric tree finch species (small tree finch Camarhynchus parvulus, medium tree finch Camarhynchus pauper, and large tree finch: Camarhynchus psittacula) that are currently recognized on Floreana Island, Galapagos Archipelago. Genetic analysis of microsatellite data from contemporary samples showed two genetic populations and one hybrid cluster in both 2005 and 2010; hybrid individuals were derived from genetic population 1 (small morph) and genetic population 2 (large morph). Females of the large and rare species were more likely to pair with males of the small common species. Finch populations differed in morphology in 1852–1906 compared with 2005/2010. An unsupervised clustering method showed (a) support for three morphological ...

Interannual and interspecific variation in intensity of the parasitic fly, Philornis downsi, in Darwin’s finches

Abstract: An integrative approach to managing host–parasite interactions that threaten species communities will benefit from identifying variation in parasite impact across host species, and host–parasite responses to annual climatic variation. We examine interannual, inter- and intraspecific variation in Philornis downsi intensity – an introduced blood sucking fly that causes high fitness costs in Darwin’s finches on the Galapagos Islands. We sampled 131 nests of six finch species (with nestling survival ⩾6 days post-hatching) between 1998 and 2005 on Santa Cruz Island. P. downsi total (per nest) and mean (per nestling) intensity differed across species and years. The woodpecker finch (Cactospiza pallida), and the large tree finch (Camarhynchus psittacula) had the highest total parasite intensity. Both species had comparatively large adult body mass, and we found a positive association between adult body mass and total parasite intensity among nestlings. P. downsi total and mean intensity was highest during the El Nino year of 1998. Surprisingly, despite a threefold difference in rainfall across lowland and highland habitats in other than the El Nino year, there was no difference in parasite intensity per nest between habitats. However, species composition of hosts and intraspecific brood size vary across habitats. Highland nests with larger broods and lower mean (per nestling) parasite intensity had higher fledging success. There was no significant effect of total parasite intensity on fledging success for intraspecific analyses. The percentage of nests with nestling mortality in each habitat ranged between 40% and 100% for all six host species.

Feeding behavior of four arboreal darwin's finches: adaptations to spatial and seasonal variability

Abstract: In the Galapagos Islands climate and food abundance vary strongly among vegetation zones and between seasons. We studied the foraging behavior of four mainly insectivorous Darwin's finch species on Santa Cruz Island. We compared foraging behavior between (1) the arid zone, where food is scarce, with the humid Scalesia zone, where food is abundant; and (2) within each zone between dry and wet seasons. The four species used different feeding substrates in the two vegetation zones and reacted flexibly to the seasonal variation by changing feeding techniques and substrates. Species mainly specialized in resource use and feeding techniques or showed no change in niche breadth when food became more limited in dry conditions. In the arid zone during the dry season, the Large Tree Finch (Camarhynchus psittacula) relied on its powerful biting beak to bite open the bark of dry twigs. The Woodpecker Finch (Cactospiza pallida) used twigs and cactus spines to access arthropods in tree holes and was the only s...

Avian population survey in the Floreana highlands: is Darwin's Medium Tree Finch declining in remnant patches of Scalesia forest?

Abstract: Summary Island species typically exist in pathogen and predator sparse environments before human settlement, and are particularly vulnerable to the impacts of invasive species. In this study, we used the variable circular-plot method to estimate the density of birds in the highlands of Floreana Island, Galapagos Archipelago, where introduced parasites, predators, and habitat degradation are a known threat to endemic species. We recorded the number of birds seen and heard at 15 locations near Cerro Pajas Volcano in 2004 and 2008, an area that harbours the largest expanse of highland Scalesia forest on Floreana Island. We estimated the change in population density for nine bird species, including five species of Darwin's finches. We specifically address changes in population density for the locally endemic Medium Tree Finch Camarhynchus pauper, which only occurs on Floreana Island and has a small population size. Comparing 2004 and 2008, our study found lower population density in the Medium Tree Finch, but stable population density in Small Tree Finch C. parvulus and Large Tree Finch C. psittacula. Based on data from three additional highland sites surveyed in 2008, we estimate that the maximum size of the Medium Tree Finch population is 1,620 individuals. In addition to the survey data, we observed breeding males in 2006 and 2008. We found: (1) low nesting success (six out of 63 nests produced fledglings) and high Philornis downsi parasite intensity, and (2) a biased age structure of the breeding population. No breeding males were one year old in 2006, and no males were five years old in either study year, indicating low reproductive success as well as limited lifespan. This research has contributed to the recent re-evaluation by IUCN, which has changed the Red List status of the Medium Tree Finch from 'Vulnerable' to 'Critically Endangered'.

Jack-of-all-trades or master of one? Variation in foraging specialisation across years in Darwin’s Tree Finches (Camarhynchus spp.)

Abstract: Theory predicts that species should have wider foraging niches during conditions of resource scarcity. However, empirical evidence to date has shown mixed patterns, including studies of Darwin’s finches that have found narrower foraging niches during conditions of resource scarcity. Here, we compare foraging behaviour in three species of Darwin’s Tree Finches (Camarhynchus spp.) in a dry versus wet year on Floreana Island to examine the change in foraging breadth under conditions of resource scarcity. We provide descriptive data on diet, foraging substrate, technique, height, and foraging time across the Small Tree Finch (C. parvulus), Medium Tree Finch (C. pauper), and Large Tree Finch (C. psittacula). During dry versus wet years, we made the following predictions: (1) lower intraspecific niche breadth (that is, a higher level of specialisation), (2) lower interspecific overlap in all foraging parameters, and (3) longer foraging times due to relative resource scarcity. Our findings showed that the Small and Medium Tree Finches were generalist foragers, while the Large Tree Finch was a specialist. Resource specialisation varied across years of differing rainfall: both generalist species were less specialised (higher Shannon diversity index) during the dry year, while the specialist species was more specialised (lower Shannon diversity index).