One of the principal drivers of biodiversity loss is habitat loss due to land conversion for agriculture. Understanding how agricultural landscapes can be more biodiverse is critical in devising a ...working lands conservation plan. For at least 20 years, some bird populations in the Galapagos have been in sharp decline, especially in the agricultural zone. Since 2010, we found that the relative abundance of ten out of eleven monitored landbird species has further decreased. We examined the existing habitat structures in the agricultural zone of Santa Cruz, historically established in former areas of native humid forest (
Scalesia
), and analyzed which structures associated with higher landbird diversity and abundance of four declining species. We conducted standardized point counts and surveyed surrounding vegetation during the breeding period. Landbird diversity was highest in forest and coffee sites and least diverse in pasture sites. Main predictors of higher landbird diversity were forest patch presence, increased abundance of native vegetation and lower elevations. Main predictors of higher landbird relative abundance were percentage of forest in the surrounding 200 m radius buffer and forest patch presence. Our results suggest that to increase the contribution of farmlands to landbird conservation during the reproductive period, habitat management efforts should be targeted at increasing forest patches and/or corridors, particularly within pasture farms. Nevertheless, to ensure sustainability of these measures, economic value to the considered farmlands needs to be secured, social perspectives incorporated and other important threats to landbirds assessed.
Toxoplasma gondii is a zoonotic intracellular parasite of particular concern in the conservation of wildlife due to its ability to infect all homeotherms and potentially cause acute fatal disease in ...naive species. In the Galapagos (Ecuador), an archipelago composed of more than a hundred islets and islands, the presence of T. gondii can be attributed to human-introduced domestic cats, but little is known about its transmission in wildlife populations. We compared the prevalence of antibodies against T. gondii in sympatric Galapagos wild bird species that differ in diet and contact with oocyst-contaminated soil to determine the relative importance of trophic habits as an exposure factor. Plasma samples were obtained from 163 land birds inhabiting Santa Cruz, one of the cat-inhabited islands, and from 187 seabirds breeding in cat-free surrounding islands (Daphne Major, North Seymour, and South Plaza). These samples were tested for the presence of T. gondii antibodies using the modified agglutination test (MAT ≥ 1:10). All seven species of land birds and 4/6 species of seabirds presented seropositive results. All great frigatebirds (Fregata minor) (N = 25) and swallow-tailed gulls (Creagrus furcatus) (N = 23) were seronegative. Prevalence ranged from 13% in Nazca boobies (Sula granti) to 100% in Galapagos mockingbirds (Mimus parvulus). It decreased from occasional carnivores (63.43%) to granivores-insectivores (26.22%), and strict piscivores (14.62%). These results indicate that the consumption of tissue cysts poses the highest risk of exposure to T. gondii for Galapagos birds, followed by the ingestion of plants and insects contaminated by oocysts as important transmission pathways.
Invasive alien parasites and pathogens are a growing threat to biodiversity worldwide, which can contribute to the extinction of endemic species. On the Galápagos Islands, the invasive parasitic fly ...Philornis downsi poses a major threat to the endemic avifauna. Here, we investigated the influence of this parasite on the breeding success of two Darwin's finch species, the warbler finch (Certhidea olivacea) and the sympatric small tree finch (Camarhynchus parvulus), on Santa Cruz Island in 2010 and 2012. While the population of the small tree finch appeared to be stable, the warbler finch has experienced a dramatic decline in population size on Santa Cruz Island since 1997. We aimed to identify whether warbler finches are particularly vulnerable during different stages of the breeding cycle. Contrary to our prediction, breeding success was lower in the small tree finch than in the warbler finch. In both species P. downsi had a strong negative impact on breeding success and our data suggest that heavy rain events also lowered the fledging success. On the one hand parents might be less efficient in compensating their chicks' energy loss due to parasitism as they might be less efficient in foraging on days of heavy rain. On the other hand, intense rainfalls might lead to increased humidity and more rapid cooling of the nests. In the case of the warbler finch we found that the control of invasive plant species with herbicides had a significant additive negative impact on the breeding success. It is very likely that the availability of insects (i.e. food abundance)is lower in such controlled areas, as herbicide usage led to the removal of the entire understory. Predation seems to be a minor factor in brood loss.
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.
The Avian Vampire Fly,
Philornis downsi
, has invaded the Galapagos Islands, where it causes high mortality of endemic and native landbird species, including most species of Darwin’s finches. Control ...methods are under development, but key information is missing about the reproductive biology of
P. downsi
and the behavior of flies in and near nests of their hosts. We used external and internal nest cameras to record the behavior of
P. downsi
adults within and outside nests of the Galapagos Flycatcher,
Myiarchus magnirostris
, throughout all stages of the nesting cycle. These recordings showed that
P. downsi
visited flycatcher nests throughout the day with higher fly activity during the nestling phase during vespertine hours. The observations also revealed that multiple
P. downsi
individuals can visit nests concurrently, and that there are some interactions among these flies within the nest. Fly visitation to nests occurred significantly more often while parent birds were away from the nest than in the nest, and this timing appears to be a strategy to avoid predation by parent birds. We report fly mating behavior outside the nest but not in the nest cavity. We discuss the relevance of these findings for the adaptive forces shaping
P. downsi
life history strategies as well as rearing and control measures.
The introduced smooth-billed ani
Crotophaga ani
has become widespread across the Galápagos archipelago in the past half-century. It is known to predate upon a range of native and endemic species, and ...is a potential vector for the spread of invasive plants and parasites. Here we report previously undocumented examples of smooth-billed ani predation in Galápagos, including that of an endemic racer snake and a scorpion. We highlight the possibility of smooth-billed anis having a serious impact on the endemic Galápagos carpenter bee, a major pollinator, as well as native and endemic Lepidopterans and other invertebrates. In addition, we report smooth-billed ani predation of other introduced species and note the importance of further research on the wide-scale impacts of smooth-billed anis in Galápagos and their role within the archipelago’s ecological networks.
Most of the species of the genus Philornis are obligate parasites of birds' nests, especially affecting small populations. However, research on factors influencing its distribution is scarce. This ...study focuses on analyzing some elements that facilitate the parasitism of this genus on several species of birds in continental Ecuador. From a sample obtained over two years (2019-2020) in five different locations on the country's coast, 693 nests of land birds and raptors were analyzed. Of these, 13% were parasitized. Two Philornis species already reported for Ecuador (Philornis downsi, P. niger) and two morphotypes not previously registered in the country were recorded, preliminarily classified as P. sp. nr. bellus and P. sp. nr. falsificus. The species with the highest proportion was P. downsi, both in terms of nest prevalence and intensity. Each species of the parasite showed an affinity for one or more families of birds and it was evidenced that the shape of the nest facilitates the prevalence of Philornis. The prevalence of Philornis decreases in higher places in the dry coastal forests. The probability of infection was also influenced by habitat alteration: nests from disturbed sites have a higher prevalence of parasites than nests with natural forest (P = 0.002). The present study strengthens the existing knowledge about different environmental factors that influence Philornis parasitism birds of continental Ecuador.
Populations of several species of birds endemic to the Galápagos Islands have declined during recent decades, including endemic Little Vermilion Flycatchers (Pyrocephalus nanus). Understanding the ...reasons for the low breeding success of this species is a prerequisite for developing efficient conservation strategies. Studies of sympatric Darwin's finches suggest two potential reasons: parasitism by the invasive parasitic fly Philornis downsi and extreme climatic events. We investigated the role of each in the breeding success of Little Vermilion Flycatchers during three breeding seasons in the agricultural zone of Isabela Island. We found that Little Vermilion Flycatchers were severely affected by P. downsi, depending on the time of breeding. Nest success was high early in the breeding season (60% were successful) when rates of P. downsi prevalence and intensity were low, but nest success was zero and all nests were infested later in the breeding season. Philornis downsi prevalence and intensity increased with increasing temperature. Both low and high levels of rainfall had a negative effect on nest survival. A parasite removal experiment using insecticide confirmed the detrimental effect of the invasive parasite; nests infested with P. downsi had significantly lower nest success than treated nests. Injection of insecticide into nest bases can be an efficient short-term way to increase the nesting success of Little Vermilion Flycatchers, but finding long-term measures to control the P. downsi population is of utmost importance.
Understanding the mechanisms underlying speciation remains a challenge in evolutionary biology. The adaptive radiation of Darwin's finches is a prime example of species formation, and their study has ...revealed many important insights into evolutionary processes. Here, we report striking differences in mating signals (songs), morphology and genetics between the two remnant populations of Darwin's mangrove finch Camarhynchus heliobates, one of the rarest species in the world. We also show that territorial males exhibited strong discrimination of sexual signals by locality: in response to foreign songs, males responded weaker than to songs from their own population. Female responses were infrequent and weak but gave approximately similar results. Our findings not only suggest speciation in the mangrove finch, thereby providing strong support for the central role of sexual signals during speciation, but they have also implications for the conservation of this iconic bird. If speciation is complete, the eastern species will face imminent extinction, because it has a population size of only 5-10 individuals.
Tool-use is widespread among animals, but except in primates the development of this behaviour is poorly known. Here, we report on the first experimental study to our knowledge of the mechanisms ...underlying the acquisition of tool-use in a bird species. The woodpecker finch Cactospiza pallida, endemic to the Galápagos Islands, is a famous textbook example of tool-use in animals. This species uses modified twigs or cactus spines to pry arthropods out of tree holes. Using nestlings and adult birds from the field, we tested experimentally whether woodpecker finches learn tool-use socially. We show that social learning is not essential for the development of tool-use: all juveniles developed tool-use regardless of whether or not they had a tool-using model. However, we found that not all adult woodpecker finches used tools in our experiments. These non-tool-using individuals also did not learn this task by observing tool-using conspecifics. Our results suggest that tool-use behaviour depends on a very specific learning disposition that involves trial-and-error learning during a sensitive phase early in ontogeny.
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