SPACE USE, DIURNAL MOVEMENT, AND ROOSTING OF A VARIEGATED ANTPITTA (GRALLARIA VARIA) IN CENTRAL AMAZONIA

Abstract ∙ The Variegated Antpitta (Grallaria varia) is the largest member of the terrestrial insectivores guild within its Amazonian range. Despite the bird’s large size and loud vocalizations, however, basic aspects of G. varia’s natural history remain poorly understood. In this study, we conducted intensive tracking of one individual in a nature reserve in the state of Amazonas, Brazil, describing ‐ for the first time with radio telemetry ‐ space use, movement patterns, and roosting sites of G. varia. Over the course of 50 days in July and August 2017, the tracked individual moved slowly through a home range covering ∼ 17.6 ha and was generally quiet, singing at only two of 68 locations that together comprised its home range. Of five roosting sites, four included visual observations where the bird slept 3–7 (mean 4.5) m aboveground in relatively open mid‐story trees. We found no evidence of commutes to regular roost sites as all nocturnal locations were located close (mean 59.6 m, range 24–101 m) to the most recent diurnal locations. Slow movements on the ground without commutes to foraging or roosting sites help explain low capture rates in mist nets for this species. Our telemetry data suggest that G. varia home range may be larger than previously estimated in studies that relied heavily on bird vocalizations to determine area needs, though such methods may yield adequate results at times when birds vocalize frequently. Regardless, large area requirements help to explain the disappearance of G. varia documented in tropical forest fragments.Resumo ∙ Uso do espaço, movimento diurno e áreas de dormitório do tovacuçu (Grallaria varia) na Amazônia Central O tovacuçu (Grallaria varia) é o maior dos insetívoros terrestres dentro da sua distribuição na Amazônia. Apesar do seu tamanho e vocalizações altas, alguns aspectos básicos da história natural de G. varia ainda são pouco compreendidos. Neste estudo, nós realizamos o rastreamento intensivo de um indivíduo em uma reserva natural no estado do Amazonas, Brasil, descrevendo ‐ pela primeira vez com rádio‐telemetria ‐ o uso do espaço, padrões de movimento, e poleiros noturnos de G. varia. Durante 50 dias em julho e agosto de 2017, este indivíduo de G. varia moveu‐se lentamente na sua área de vida (cobrindo aproximadamente 17,9 ha) geralmente em silêncio, cantando somente em duas das 68 localizações que, juntas, formam sua área de vida. Dos cinco poleiros noturnos encontrados, quatro incluíram observações visuais onde a ave dormiu de 3 a 7 (média 4,5) m acima do solo, em um ambiente relativamente aberto no sub‐bosque. Não encontramos evidência de viagens regulares para poleiros usados a noite, uma vez que todos os poleiros noturnos estavam perto (média 59,6; amplitude 24–101 m) das localizações diurnas mais recentes do indivíduo. Mo‐vimentos lentos no solo, sem deslocamentos para sítios de forrageamento ou poleiros noturnos, ajudam a explicar a baixa taxa de captura em redes‐de‐neblina para esta espécie. Os dados de telemetria sugerem que a área de vida de G. varia é maior do que se estimava previamente em estudos que se baseavam principalmente em vocalizações para determinar o seu tamanho, embora tais métodos possam produzir resultados adequados quando as aves vocalizam com frequência. O requerimento de grandes áreas de vida ajuda a explicar o desaparecimento de registros de G. varia em fragmentos de floresta tropical

Recovery potential of understory bird communities in Amazonian rainforest fragments

Understory bird communities have been studied in a series of Amazonian rainforest fragments near Manaus, Brazil for about 20 years. Previous analysis of standardized mist-net samples revealed considerable temporal dynamism in capture rates, with communities in fragments responding to growth or cutting of the second growth matrix. This pattern was superimposed on expected fragment size effects among the 1-, 10-, and 100-ha fragments. Here we extend our earlier analysis of landscape effects by separately considering 1- and 10-ha fragments, with the goal of describing the recovery of bird communities in fragments surrounded by abandoned second growth. Most guilds, with the exception of terrestrial insectivores, appear to be on a trajectory to return to pre-isolation abundance in 10-ha fragments within about 40 years. Although some guilds showed similar recovery in 1-ha fragments, these were mostly species also common in second growth. Our results suggest that matrix development can allow bird communities to approach pre-isolation structure in fragments of at least 10 ha, but we emphasize that this conclusion represents a best-case scenario facilitated by the proximity to primary forest of the fragments we studied

Forest fragmentation alters microhabitat availability for Neotropical terrestrial insectivorous birds

Many insectivorous birds of the tropical rainforest understory, particularly terrestrial species, are prone to local extinctions in fragmented forests. We evaluated the hypothesis that vegetation structural changes in rainforest fragments reduce the availability of microhabitats used by terrestrial insectivores. Near Manaus, Brazil, we compared the vegetation in forest fragments to the vegetation in a continuous forest site where nine species of terrestrial insectivores were observed foraging. Our focal species included those that are extinction prone in fragments (Myrmornis torquata [Wing-banded Antbird], Grallaria varia [Variegated Antbird], Hylopezus macularius [Spotted Antpitta]), a fragmentation-tolerant species (Myrmothera campanisona [Thrush-like Antpitta]), and species that have and intermediate response (Myrmeciza ferruginea [Ferruginous-backed Antbird], Formicarius colma [Rufous-capped Anttrush], Formicarius analis [Black-faced Antthrush], Conopophaga aurita [Chestnut-belted Gnateater], and Corythopis torquata [Ringed Antpipit]). To quantify vegetation, we measured sixteen habitat variables in 8-m radius plots where birds were observed foraging as well as random points in continuous forest and forest fragments of 1-, 10-, and 100-ha. Four principal components were produced from a principal component analysis and we selected a variable (leaf litter depth, plant cover 3-10. m, density of plants 1-2. m, and plant cover >20. m) from each principal component for our fragment vs continuous forest comparisons. Using Markov chain Monte Carlo (MCMC) simulation, we estimated the probabilities that the density of plants 1-2. m, proportion of plant cover 3-10. m, and leaf litter depth increased with decreasing fragment area and also exceeded the values associated with fragmentation-sensitive species. We also tested the prediction that plant cover >20. m decreased in forest fragments and that those sites became more open than typical sites used by our focal species. Our predictions were strongly supported: decreasing fragment size was correlated with increasing density of tall plants, increasing mid-story vegetation cover, decreased canopy cover, and increasing leaf litter depth. Even if our focal species are able to disperse to small forest fragments, our results suggest that they may not find enough appropriate habitat. © 2015 Elsevier Ltd

Diversidade, biomassa, e estrutura trófica de uma comunidade de aves de floresta tropical na Amazônia central

Amazonian forest bird communities are among the richest in the world. Even so, relatively little is known about the organization of the entire avian community at local scales or about differences across Amazonia. These are fundamental data not only for understanding the processes generating and maintaining tropical diversity, but also as a baseline for evaluating anthropogenic changes to Amazonian forests. Here we provide a description of the entire bird community for a 100 ha plot of terra firme forest at the Biological Dynamics of Forest Fragments Project, near Manaus, Brazil, based on spot-map and mist net surveys augmented by additional field and analytical techniques. Although our results are from a single plot surveyed in a single year, our methods and interpretation reflect nearly 30 years of ornithological research at the site. We found 228 species on the plot, of which 207 were considered part of the core regional avifauna. Median density was five individuals/100 ha. Only 13 species (6% of the core species) had densities ≥ 20 individuals on the plot, although 55 species (27%) had ≤ 2 individuals. No species had territories smaller than 3 ha; median territory size was 11 ha for the 103 species for which we could make reasonable estimates. Measured by numbers of species or individuals, the plot was dominated by insectivores (54% of species, 62% of individuals). Biomass, however, was dominated by frugivores and granivores (59%). Compared to available data from other Amazonian forests, our site appears to have comparable richness of a similar set of species, but lower density and greater patchiness. Our results suggest that the area required to support populations of many species will be even greater in central Amazonia than in western Amazonia

Effects of a regenerating matrix on the survival of birds in tropical forest fragments

Background Vast areas of lowland neotropical forest have regenerated after initially being cleared for agricultural purposes. The ecological value of regenerating second growth to forest-dwelling birds may largely depend on the age of the forest, associated vegetative structure, and when it is capable of sustaining avian demographics similar to those found in pristine forest. Methods To determine the influence of second growth age on bird demography, we estimated the annual survival of six central Amazonian bird species residing in pristine forest, a single 100 and a single 10 ha forest fragment, taking into consideration age of the surrounding matrix (i.e. regenerating forest adjacent to each fragment) as an explanatory variable. Results Study species exhibited three responses: arboreal, flocking and ant-following insectivores (Willisornis poecilinotus, Thamnomanes ardesiacus and Pithys albifrons) showed declines in survival associated with fragmentation followed by an increase in survival after 5 years of matrix regeneration. Conversely, Percnostola rufifrons, a gap-specialist, showed elevated survival in response to fragmentation followed by a decline after 5 years of regeneration. Lastly, facultative flocking and frugivore species (Glyphorynchus spirurus and Dixiphia pipra, respectively) showed no response to adjacent clearing and subsequent regeneration. Conclusions Our results in association with previous studies confirm that the value of regenerating forest surrounding habitat patches is dependent on two factors: ecological guild of the species in question and second growth age. Given the rapid increase in survival following succession, we suggest that the ecological value of young tropical forest should not be based solely on a contemporary snapshot, but rather, on the future value of mature second growth as well

Avian ecological succession in the Amazon: A long-term case study following experimental deforestation

Approximately 20% of the Brazilian Amazon has now been deforested, and the Amazon is currently experiencing the highest rates of deforestation in a decade, leading to large-scale land-use changes. Roads have consistently been implicated as drivers of ongoing Amazon deforestation and may act as corridors to facilitate species invasions. Long-term data, however, are necessary to determine how ecological succession alters avian communities following deforestation and whether established roads lead to a constant influx of new species. We used data across nearly 40 years from a large-scale deforestation experiment in the central Amazon to examine the avian colonization process in a spatial and temporal framework, considering the role that roads may play in facilitating colonization. Since 1979, 139 species that are not part of the original forest avifauna have been recorded, including more secondary forest species than expected based on the regional species pool. Among the 35 species considered to have colonized and become established, a disproportionate number were secondary forest birds (63%), almost all of which first appeared during the 1980s. These new residents comprise about 13% of the current community of permanent residents. Widespread generalists associated with secondary forest colonized quickly following deforestation, with few new species added after the first decade, despite a stable road connection. Few species associated with riverine forest or specialized habitats colonized, despite road connection to their preferred source habitat. Colonizing species remained restricted to anthropogenic habitats and did not infiltrate old-growth forests nor displace forest birds. Deforestation and expansion of road networks into terra firme rainforest will continue to create degraded anthropogenic habitat. Even so, the initial pulse of colonization by nonprimary forest bird species was not the beginning of a protracted series of invasions in this study, and the process appears to be reversible by forest succession. © 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd

Effects of a regenerating matrix on the survival of birds in tropical forest fragments

Background: Vast areas of lowland neotropical forest have regenerated after initially being cleared for agricultural purposes. The ecological value of regenerating second growth to forest-dwelling birds may largely depend on the age of the forest, associated vegetative structure, and when it is capable of sustaining avian demographics similar to those found in pristine forest. Methods: To determine the influence of second growth age on bird demography, we estimated the annual survival of six central Amazonian bird species residing in pristine forest, a single 100 and a single 10 ha forest fragment, taking into consideration age of the surrounding matrix (i.e. regenerating forest adjacent to each fragment) as an explanatory variable. Results: Study species exhibited three responses: arboreal, flocking and ant-following insectivores (Willisornis poecilinotus, Thamnomanes ardesiacus and Pithys albifrons) showed declines in survival associated with fragmentation followed by an increase in survival after 5 years of matrix regeneration. Conversely, Percnostola rufifrons, a gap-specialist, showed elevated survival in response to fragmentation followed by a decline after 5 years of regeneration. Lastly, facultative flocking and frugivore species (Glyphorynchus spirurus and Dixiphia pipra, respectively) showed no response to adjacent clearing and subsequent regeneration. Conclusions: Our results in association with previous studies confirm that the value of regenerating forest surrounding habitat patches is dependent on two factors: ecological guild of the species in question and second growth age. Given the rapid increase in survival following succession, we suggest that the ecological value of young tropical forest should not be based solely on a contemporary snapshot, but rather, on the future value of mature second growth as well. © 2020 The Author(s)

Rates of species loss from Amazonian forest fragments

In the face of worldwide habitat fragmentation, managers need to devise a time frame for action. We ask how fast do understory bird species disappear from experimentally isolated plots in the Biological Dynamics of Forest Fragments Project, central Amazon, Brazil. Our data consist of mist-net records obtained over a period of 13 years in 11 sites of 1, 10, and 100 hectares. The numbers of captures per species per unit time, analyzed under different simplifying assumptions, reveal a set of species-loss curves. From those declining numbers, we derive a scaling rule for the time it takes to lose half the species in a fragment as a function of its area. A 10-fold decrease in the rate of species loss requires a 1,000-fold increase in area. Fragments of 100 hectares lose one half of their species in < 15 years, too short a time for implementing conservation measures

Twenty years later: An update to the birds of the biological dynamics of forest fragments project, Amazonas, Brazil

Although species lists from throughout Amazonia have become available, relatively complete inventories based on longterm work remain rare. Longitudinal comparisons at well-studied sites provide the best opportunities for describing communities and identifying changes in regional avifaunas. Within central Amazonia, no region has received as much consistent ornithological coverage as the terra firme forests north of Manaus, Brazil, at the Biological Dynamics of Forest Fragments Project (BDFFP). Here we provide an updated list of the area, including notes on all species added between 1997 and 2017. We recorded 21 species new for the site, most of which (>75%) are birds that prefer várzea or second-growth forest. This brings the cumulative BDFFP list up to 409 species, the majority (66%) of which inhabit primary terra firme forest. Together, this confirms that the regional terra firme community had been well-characterized by the 1990s, and that species additions to the list over the last 20 years are consistent with a changing landscape as urbanization, agriculture, and second-growth spread from Manaus. The final product continues to represent the most complete avian inventory for a single site in all of lowland Amazonia. © 2017, Sociedade Brasileira de Ornitologia. All rights reserved

Heterogeneous movement of insectivorous Amazonian birds through primary and secondary forest: A case study using multistate models with radiotelemetry data

Given rates of deforestation, disturbance, and secondary forest accumulation in tropical rainforests, there is a great need to quantify habitat use and movement among different habitats. This need is particularly pronounced for animals most sensitive to disturbance, such as insectivorous understory birds. Here we use multistate capture-recapture models with radiotelemetry data to determine the successional stage at which within-day movement probabilities of Amazonian birds in secondary forest are similar to those in primary forest. We radio-tracked three common understory insectivore species in primary and secondary forest at the Biological Dynamics of Forest Fragments project near Manaus, Brazil: two woodcreepers, Glyphorynchus spirurus (n=19) and Xiphorhynchus pardalotus (n=18), and the terrestrial antthrush Formicarius colma (n=19). Forest age was a strong predictor of fidelity to a given habitat. All three species showed greater fidelity to primary forest than to 8-14-year-old secondary forest, indicating the latter's relatively poor quality. The two woodcreeper species used 12-18-year-old secondary forest in a manner comparable to continuous forest, but F. colma avoided moving even to 27-31-year-old secondary forest-the oldest at our site. Our results suggest that managers concerned with less sensitive species can assume that forest reserves connected by 12-18-year-old secondary forest corridors are effectively connected. On the other hand, >30. years are required after land abandonment before secondary forest serves as a primary forest-like conduit for movement by F. colma; more sensitive terrestrial insectivores may take longer still. © 2015 Published by Elsevier Ltd