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Opportunistic predation of a Common Scale-backed Antbird (Willisornis poecilinotus) by a Goliath bird-eating spider (Theraphosa blondi) in the Eastern Brazilian Amazon

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We report the opportunistic predation of a female Common Scale-backed Antbird (Willisornis poecilinotus) entangled in a mist-net by a Goliath bird-eating spider (Theraphosa blondi) in the Brazilian Amazon. We suggest that the predation event occurred for the following combination of reasons: the spider is common in the study area; the bird became entangled at dusk, when the spider begins its activity; and the lowest mist-net shelf was suspended close to the ground. To reduce opportunistic predation events we recommend that it is critical to keep intervals between mist-net checks to a maximum of 15 min in Amazon forests. We also emphasize that attention is required when installing mist-nets to avoid nets touching the ground when animals become trapped in them.
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... T. blondi is considered one of the biggest known spiders, reaching up to 260 mm in length (Marshall and Uetz, 1993;Foelix, 1996;Almeida et al., 2018). It presents predominantly nocturnal activity and its diet is considered generalist, being known to feed on vertebrates of similar size or slightly smaller than the spider, such as amphibians (Menin et al., 2005) and birds (Carvalho et al., 2016). It has a wide geographic distribution, and can be found in tropical forests of the southeast of Venezuela and Guyana, and in the north of the Brazilian Amazon forest (Saul-Gershenz, 1996). ...
... It has a wide geographic distribution, and can be found in tropical forests of the southeast of Venezuela and Guyana, and in the north of the Brazilian Amazon forest (Saul-Gershenz, 1996). One of the popular names of T. blondi is "Goliath bird-eating spider", due to the record of a specimen that preyed on a female of the bird species Willisornis poecilinotus (Cabanis, 1847) (Carvalho et al., 2016). ...
... Nyffeler et al., 2017), and two concerning vertebrate prey (e.g. Menin et al., 2005;Carvalho et al., 2016), indicating a gap on the knowledge about their food items. Therefore, this record helps to understand the natural history of T. blondi and L. annulata, highlighting the existence of important trophic connections between these groups. ...
... Opportunistic predation of birds in MNs varies geographically (Spotswood et al. 2012). In Brazil, although little documented, trapped birds are known to be predated by arachnids (Carvalho et al. 2016), birds of prey (Curcino et al. 2009;Ruiz-Esparza et al. 2012) and primates belonging to the family Callitrichidae (Hilário et al. 2017). An attempt of predation by a reptile has been reported, the Argentine black and white tegu (Salvator merianae) on pale-breasted thrush (Turdus leucomelas) (Santos and Vaz-Silva 2012). ...
... Previous studies have provided central points to mitigate the rate of predation and mortality of birds in MN, such as (i) reduction of the observation interval to 15-20 min (Churchwell and Barton 2006;Hilário et al. 2017); (ii) attention to the locations of MNs and maintaining safe ground clearance to protect against ground predators (Carvalho et al. 2016); and (iii) placement of MNs far enough from branches to limit predator access (Hilário et al. 2017). We agreed with these recommendations because the predators observed here also used the ground and branches to access birds trapped in MNs. ...
Article
Mist netting is the most popular method for capturing birds, but it can increase the predation rates of individuals trapped in the nets. From 2008 to 2017, we recorded eight instances of opportunistic bird predation from mist nets (MNs) in a matrix mixing restored forest and fragments of semideciduous seasonal forest in southeastern Brazil, three times (37.5%) by exotic primates and five times (62.5%) by birds of prey. Overall predation rates (1.17–1.20%) at these two sites were considered high but were lower than in other Brazilian studies. Placing MNs near the edges of forest fragments may have allowed attacks by either forest predators or marmosets, which are exotic edge species. Some previously described precautions may decrease the predation rates of birds in MNs, such as shorter observation intervals, greater attention to given site selection and maintaining a safe distance between the MNs and the ground.
... Despite the apparent low number of casualties reported compared to the common high capture rates in the tropics, simple methodological modifications could be easily applied to minimize the number of accidents and improve animal safety without compromising research logistics and results. We therefore echo the recommendations suggested by Breviglieri & Pedro (2010) and Carvalho et al. (2016) that, in order to reduce predation of captured animals, visits to the mist-nets should not be more than 15-20 min apart (most of the current guidelines suggest 30 min intervals between checks). Additionally, considering the high percentage of nonflying predators that have been reported to opportunistically prey on entangled animals, mist-nets should not reach ground-level. ...
... Additionally, considering the high percentage of nonflying predators that have been reported to opportunistically prey on entangled animals, mist-nets should not reach ground-level. As recommended by Carvalho et al. (2016), the proximity of the mist-net relatively to the ground once an animal is trapped can be checked by placing an object with a similar weight of the animals which are likely to be trapped in the lowest shelf of the mist-net. These suggestions must be tested in each region, and specifically adapted to local conditions, as risk of opportunistic predation is probably siteand time-specific. ...
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Spanish title: Depredación oportunística del murciélago sedoso de cola corta (Carollia brevicauda) por el autillo orejudo (Megascops watsonii), con una recopilación de eventos de depredación sobre murciélagos en las redes de niebla. Abstract: Bat casualties caused by opportunistic predation of entangled animals during surveys employing mist-nets are scarcely reported in the scientific literature. Consequently, predator induced mortality associated with this sampling method is probably underestimated. Here, we report a predation attempt of a silky short-tailed bat (Carollia brevicauda) by a tawny-bellied screech-owl (Megascops watsonii) while the bat was entangled in the mist-net. The event took place in the Central Brazilian Amazon and represents the first report of bat predation attempt by this owl species. Additionally, we searched the literature for published records of bat predation during mist-net surveys since 1990. Twelve publications, covering at least 15 bat species and 11 predators, have reported opportunistic predation on entangled animals. We consider that predation of entangled animals is likely underreported and we recommend than in order to reduce opportunistic predation of entangled animals, researchers should: a) periodically visit the mist-nets every 15 to 20 minutes, and b) avoid that mist-nets reach ground-level once an animal becomes trapped.
... In spiders (Araneae), however, such behavior is far less well documented, as spiders are predominately predators of arthropods, with insects by far being the most dominant prey group (Nyffeler 1999;Birkhofer & Wolters 2012;Peka´r & Toft 2015). In addition, some spider species are known to occasionally include small vertebrates in their diets (McCormick & Polis 1982;Henschel 1994;Menin et al. 2005;Nyffeler & Knörnschild 2013;de Carvalho et al. 2016;Nyffeler et al. 2017). Still other spiders use plant food to supplement their diets (Nyffeler et al. 2016). ...
... Tropical spiders from the families Theraphosidae and Ctenidae accounted for 59% of the reported incidents of earthworm predation by spiders. Spiders from these families are typical generalist predators with broad feeding niches (Brunet 1998;Lapinski & Tschapka 2013;Lewis 2014;de Carvalho et al. 2016;Rick West, pers. comm.). ...
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Predation on earthworms is common in some generalist predator species, as for example several ground beetle species (Coleoptera: Carabidae) that frequently feed on earthworms. In spiders (Araneae), however, such behavior is far less well documented. A survey of reports on spiders feeding on earthworms yielded a total of 44 naturally occurring predation events. Spiders from 14 families were observed feeding on earthworms in nature, and species from two additional families consumed earthworm prey in captivity. Earthworm predation by spiders has been observed in temperate, subtropical, and tropical regions in 18 different countries. Tropical spiders from the families Theraphosidae (Mygalomorphae) and Ctenidae (Araneomorphae) accounted for 59% of the reported predation events. Reports from French Guiana document the capture of giant earthworms (0.6-1 m in length) by the giant tarantula, Theraphosa blondi (Latreille, 1804). Predation on giant earthworms by large tarantulas has also been observed in rainforest habitats in Brazil, Ecuador, Peru, and Venezuela. Wandering spiders (Ctenidae) are known to feed on earthworms in Belize, Brazil, Costa Rica, French Guiana, Guyana, and Singapore. Quite obviously, larger-sized mygalomorph and araneomorph spiders in humid tropical rainforests are predators with broad feeding niches-including earthworms and vertebrate prey in addition to arthropod prey-and this is presumed to improve the survival of these spiders. By comparison, reports of earthworm predation in temperate climate are rarer, and recent molecular studies of the diet composition of lycosid and linyphiid spider species in Swedish arable fields suggest that earthworms are not a common prey of these species.
... Mist nets were checked every ca. 20 min (Carvalho et al. 2016b). Total netting effort, calculated accordingly to Straube and Bianconi (2002), was 155.5 m 2 *h, equally divided by the two habitats. ...
Article
Effective survey methods are paramount to measure changes in species distribution, populations dynamics and to guide conservation. Mist-netting and passive acoustic monitoring are two of the most used techniques to sample bats assemblages. Yet, despite the great potential of low-cost autonomous ultrasound recorders in surveying bat assemblages, we lack thorough assessments of their performance in relation to more established survey methods. Taking advantage of the rich bat fauna of the northeastern Brazilian Amazon, we set out to i) investigate the complementarity of mist-netting and acoustic surveys in sampling bats in forest and savannah habitats in the Savannahs of Amapá and ii) undertake a cost-effectiveness evaluation of using one, two or three recorders per sampling site to simultaneously survey bat assemblages. The two methods show complementary, and overall species diversity recorded with mist nets was higher than with acoustic recorders. However, species diversity was higher with acoustic recorders than with mist nets when considering a reduced (n < 3) number of transects. In addition, we found a gain in species diversity when using more than one acoustic recorder in forest habitats, despite the low cost-effectiveness. However, there were no differences between the diversity using one, two or three acoustic recorders in savannah. Due to possible device malfunction, we recommend the use of at least two acoustic recorders in both habitats to reduce the likelihood of data loss. The use of low-cost bioacoustic recorders in bat surveys can help to address critical knowledge gaps for poorly known aerial-hawking insectivores and support evidence-based conservation strategies.
... During each visit (sampling night), we captured bats using eight mist nets (12 × 3 m in size and 14 mm mesh) per plot. The nets were set up 15 minutes before sunset (~18h:00) at ground level and remained open for 6 hours (~00h:00), being inspected every 15 minutes (Carvalho et al. 2016). The sampling effort was calculated following recommendations by Straube and Bianconi (2002), totalling 5.184 m 2 .h ...
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Variations in environmental conditions along gradients play an important role in species distribution through environmental filtering of morphological and physiological traits; however, their effects on bat diversity remain poorly understood. Here, we investigate the effect of the distance to the nearest watercourse, terrain elevation, vegetation clutter, basal area and canopy height on taxonomic, functional and phylogenetic diversity and on the predominance of some functional traits (body mass, wing morphology and trophic level) of bat assemblages (phyllostomid and mormoopid bats) in a terra firme forest, in the northeastern Brazilian Amazon. We captured bats using mist nets in 15 permanent plots over a 25 km ² area of continuous forest. We captured 279 individuals belonging to 28 species with a total of 77.760 m ² .h of sampling effort. Our results showed that bat richness increases as a function of distance to the nearest watercourse and that the assemblage also changes, with more diverse taxonomic and functional groups in areas further from the watercourse. Furthermore, elevation positively affects species richness, and the basal area of the forest positively influences the average body mass of bats. Taken together, our results demonstrate that subtle variations in the environmental conditions along a local scale gradient impact on the main dimensions of bat diversity in primary forests.
... As such, this welfare issue is not often taken into account when mist-netting surveys are being designed. Best practice recommendations for mist-netting currently state that nets should be checked every 15-20 minutes and the lowest shelf of the nets set at a safe height (Bosco Breviglieri & Pedro 2010, de Carvalho et al. 2016, de Carvalho et al. 2018, Serra-Gonçalves et al. 2017). To reduce the possibility of predation events, we recommend that the minimum time threshold described in these sources (15 minutes) should be used, and emphasize that these checking intervals should be completed at all times (even when bat activity is low). ...
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Predation of entangled bats captured in mist-nets is common but infrequently documented. As such, this welfare issue is often not considered when mist-netting surveys are being designed. Margays (Leopardus wiedii) are small neotropical cats that are known to have a varied diet and exhibit opportunistic hunting behaviour. Despite bats not having been frequently reported as a prey item for margays, studies on this felid's feeding ecology remain scarce. We discuss the potential for margays to feed on bats when they become entangled in mist nets, providing two examples from Cusuco National Park, Honduras. In light of this, we provide recommendations as to how such opportunistic predation events can be mitigated in future surveys.
... Campos eSilva and de Meirelles, 2016;Carvalho et al., 2016), lizards(Coêlho et al., 2019), and snakes (Da Silva et al., 2019). Our observations corroborate the findings of Da Silva et al. (2019) who reported the predation of a Leptodeira annulata by T. blondi in the municipality of Anapú, state of Pará, Brazil. ...
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During a pitfall trap inspection, we noticed a D. dichrous moving erratically on the soil, and out of the buckets. Its movements were not compatible with what was expected of this animal. As we removed the drift fence that constitutes the trap, we found a T. blondi with the chelicerae grasped in the snake’s midbody, already feeding on it. Initially, we observed the snakes’ defensive behaviour, as it was rotating its body. Finally, after 12 minutes, these movements ceased, and the spider kept on feeding. This whole event lasted for approximately 20 minutes.
... However, West (2019, personal communication) once observed a hummingbird being eaten by a tarantula (Fig. 8.1b) although he did not observe whether the bird was caught by the spider. A report was published by Carvalho et al. (2016), regarding a common scale-backed antbird (Willisornis poecilinotus Cabanis, 1847; Passeriformes, Thamnophilidae) entangled in a mist net installed close to the ground, thus allowing an individual of T. blondi to take the prey. As for mammals, large tarantulas are clearly able to catch and prey on birds but do not do so as commonly as we imagine. ...
Chapter
The Aviculariinae spiders sensu lato are known as the American arboreal tarantulas. They are characterized mainly by having legs with few or no spines, laterally extended tarsal and metatarsal scopulae, resulting in a spatulate appearance of the appendices, absence of spiniform setae on the prolateral maxillae, females with completely separated spermathecae, males with palpal bulb with subtegulum not extended, and long and thin embolus without keels (except Antillena). Some Aviculariinae, together with all Theraphosinae, are the only spiders that evolutionarily acquired urticating setae as a defense mechanism. The primary mechanism for releasing the urticating setae in Theraphosinae is by the friction of the legs with the abdomen, which throws the urticating setae into the air, in contrast, in most Aviculariinae the releasing mechanism occurs by direct contact. The Aviculariinae tarantulas have received considerable taxonomic and biological attention and the validity as a monophyletic group has been discussed extensively. Some phylogenetic studies suggest at least two subfamilies for the American arboreal tarantulas and their kin: Aviculariinae and Psalmopoeinae. Likewise, the phylogenetic relationships of these groups have been questioned, linking these tarantulas more closely with African or American taxa. Taxonomy, systematics and some aspects of its natural history, behavioral and distribution are addressed in this chapter.
... However, West (2019, personal communication) once observed a hummingbird being eaten by a tarantula (Fig. 8.1b) although he did not observe whether the bird was caught by the spider. A report was published by Carvalho et al. (2016), regarding a common scale-backed antbird (Willisornis poecilinotus Cabanis, 1847; Passeriformes, Thamnophilidae) entangled in a mist net installed close to the ground, thus allowing an individual of T. blondi to take the prey. As for mammals, large tarantulas are clearly able to catch and prey on birds but do not do so as commonly as we imagine. ...
Chapter
Theraphosids interact with numerous species from invertebrates to humans. Their diet predominantly consists of insects, spiders and worms; however, their prey cover a wide range of taxa including mammals, birds, reptiles, fish and even the very toxic poison dart frogs. Practically blind, they detect prey by vibrations and may also use odors. Their predatory activity may affect the distribution of other predatory species such as other spiders or scorpions. Furthermore, predation may include cannibalism between females. Despite a variety of anti-predatory strategies that include urticating hairs, burrows, or special coloration, theraphosids are preyed upon by vertebrates such as coatis but also by invertebrates including the giant earthworm and other spiders. Parasitoid hawk wasps hunt tarantulas and they are also parasitized by flies. Tarantulas may be found in commensalistic associations with toads or bromeliads. In their natural range, they also interact with humans and native people from different regions of America who use them for food or as part of traditional medicine. The diversity of these interactions and adaptations may be considered as the result of a long evolutionary history.
... However, West (2019, personal communication) once observed a hummingbird being eaten by a tarantula (Fig. 8.1b) although he did not observe whether the bird was caught by the spider. A report was published by Carvalho et al. (2016), regarding a common scale-backed antbird (Willisornis poecilinotus Cabanis, 1847; Passeriformes, Thamnophilidae) entangled in a mist net installed close to the ground, thus allowing an individual of T. blondi to take the prey. As for mammals, large tarantulas are clearly able to catch and prey on birds but do not do so as commonly as we imagine. ...
Chapter
Studying morphology of Theraphosidae spiders can be very challenging, especially if the main objective is assembling characters for systematics. Such spiders present a homogeneous morphology, which, according to some specialists, has driven the attention of systematists to other groups of Araneae. Nevertheless, a great diversity of cuticular structures has been overlooked until the widespread use of scanning electron microscopy (SEM) in the last years for theraphosids. Among all mygalomorphs, Theraphosidae spiders possess the greatest variety of cuticular features. Data regarding cuticular features are still incipient, but we have been gathering massive quantity of SEM images of all parts of the spider body, revealing interesting structures to be used in systematics and investigated for functional morphology. In addition to the well-known tarsal adhesive setae of theraphosids and the urticating setae of Theraphosinae, we found putative chemosensitive setae, a great variety of stridulating setae, distinct morphologies of leg and palpal structures, including cuticular projections, labial and maxillary cuspules, trichobothria, as well as other enigmatic features. In this chapter, we aim to present a comprehensive revision of cuticular features of New World Theraphosidae spiders, with descriptions and micrographs.
... Other predators may also be attracted to mist nets such as deer (Allan, 1978), spiders (Carvalho et al., 2016), praying mantis (Nyffeler et al., 2017) and ants (Ross, 2010;Bichinski, 2015). Ant predation is related to birds caught near ground level that are vulnerable to attack, so we need to avoid arming nets near anthills (Ross, 2010). ...
Article
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The use of mist nets is a highly used method among researchers due to their efficiency in capture birds and bats. However, trapped animals are vulnerable to predator action. During three ornithological studies carried out in a forest fragment from southwest Amazonia, we recorded 15 predation events, with predation rate of 1.5%. Among predators, 26.7% (n = 4) of the cases were related to primates, 13.3% (n = 2) related to army ants, 13.3% (n = 2) related to an unidentified hawk species and in 46.7% (n = 7) of the cases the predators did not identified. Preventing predator access to mist nets and reducing network monitoring time are some of the measures that can prevent these events.
... One problem associated with sampling with mist nets, for both bats and birds, is the risk of opportunistic predation events while individuals are in the net (Breviglieri et al., 2010;Spotswood et al., 2012;Carvalho et al., 2016). This type of predation has been suggested to be the second biggest cause of bird deaths in mist nets, after stress (Spotswood et al., 2012). ...
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The Amazon region is made up of a mosaic of important habitats scattered throughout the rainforests, which differ in vegetation structure, basal area, primary productivity, biomass and production of flowers and fruits. Consequently, species richness and abundance also vary between these habitat types, in part explaining the high levels of richness found in the Amazon region. Here, we sampled bats using mist nets in three Amazonian habitats to explore variation in richness, abundance and community composition between habitats and seasons, and test for variation in the number and composition of bats captured in different mist net shelves. Overall abundance was highest in Amazonian savannahs, which is probably due to these habitats being more complex at the landscape scale-being composed of areas of savannah interspersed with forest fragments, gallery forests and palm stands. Abundance was also higher in the rainy season in savannahs and terra firme forest, and in the dry season in campinarana. In all habitats, bats were most frequently captured between 0.7 and 2.4 m from the ground. These results have important implications for our understanding of the ecology of, and habitat use by bats in the Amazon, particularly in the less well-studied habitat types of Amazonian savannah and campinarana. In addition, knowledge of the distribution of bat captures between mist net shelves serves to highlight that nets need not be set so close to the ground to maintain sampling efficiency, which is important as it may help to reduce opportunistic predation events of individuals caught in the lowest mist net shelf.
... Escarlate-Tavares and Pessôa 2005), and the collection of opportunistic observations of predation in the wild (e.g. Carvalho et al. 2016;Hilário et al. 2017;Serra-Gonçalves et al. 2017). Knowledge is particularly scarce on the interaction of bats as prey and their predators in Brazil (Costa et al. 2016), mainly because of the difficulty in making direct observations of predation events (Silva and Henderson 2012). ...
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We report an observation of predation by an Amazon tree boa, Corallus hortulanus, on an American fruit-eating bat, Artibeus sp., in an area of seasonal forest close to a small stream in the northern Brazilian Amazon. While bats appear to be one of the main food items of C. hortulanus, our observation is only the fourth such event to be recorded in the Brazilian Amazon. The Artibeus sp. individual was observed making distress (agony) calls continuously over a period of three hours, much longer than recorded on previous observations. Records of this type are important to further our knowledge on bat predators, and the defensive behavior of bats.
... They can be found on holes in the ground (used as burrows) near tributary streams in primary forest (Luizão 2004). These spiders prey on a large variety of invertebrates in the forest soil and can even capture small vertebrates (Carvalho et al. 2016). However, the ecology of these spiders is still poorly known. ...
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We present the first record for Theraphosa apophysis (Tinter, 1991) for Brazil. A male of T. apophysis was collected in São Gabriel da Cachoeira, Amazonas state, Brazil. This is the third species of Theraphosa in Brazil along with T. blondi (Latreille, 1804) and T. stirmi Rudloff & Weinmann, 2010.
... Mortality can occur due to injury, thermal stress, shock or predation (Recher et al. 1985), and researchers should strive to maintain bird mortality below 1% (Ralph et al. 1993). Predation of birds in mist nets has been reported by birds of prey, other bird species, spiders, ants, carnivorous mammals, white-tailed deer (Odocoileus virginianus), eastern cottontails (Sylvilagus floridanus), squirrels (Sciurus sp.) and eastern chipmunks (Tamius striatus) (Recher et al. 1985; Brooks 2000; Ruiz-Esparza et al. 2012; Spotswood et al. 2012; Carvalho et al. 2016). In addition, Brooks (2000) reported 17 observations of blue monkeys (Cercopithecus mitis) preying on birds in mist nets. ...
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We report predation of four birds while caught in mist nets and recommend some means of prevention. Two birds were attacked by Callitrhix jacchus and one by Saguinus midas. The predator in the fourth case was unidentified. These cases were relatively rare, affecting 0.4–4.4% of the captured birds. Two of the predated birds were caught more than 1 m above the ground and may have been accessed from branches. The other two were caught close to the ground. Reducing time intervals between net checks and cutting off branches close to nets may reduce bird predation in mist nets.
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Reports of tarantulas feeding on birds are rare and were a matter of intense debate among naturalists for centuries. The first account dates from the early eighteenth century by the German naturalist Marie Sibylla Merian, and since then only a few reliable predation events have been published. We herein report on a predation event by the arboreal tarantula Iridopelma vanini Bertani, 2012 on two Southern house wrens Troglodytes musculus Naumann, 1823 in Brazil. The spider, a male, was found feeding on a young bird on a signpost made of two wooden posts, at dusk. The following day, one of the posts was removed and the spider was found feeding on a second young bird on its nest. We also update and discuss the identification of the theraphosids involved in predation events reported in previous works.
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In this paper, 374 incidents of frog predation by spiders are reported based on a comprehensive global literature and social media survey. Frog-catching spiders have been documented from all continents except for Antarctica (>80% of the incidents occurring in the warmer areas between latitude 30° N and 30° S). Frog predation by spiders has been most frequently documented in the Neotropics, with particular concentration in the Central American and Amazon rain forests and the Brazilian Atlantic forest. The captured frogs are predominantly small-sized with an average body length of 2.76 ± 0.13 cm (usually ≈0.2–3.8 g body mass). All stages of the frogs' life cycle (eggs/embryos, hatchlings, tadpoles, emerging metamorphs, immature post-metamorphs, adults) are vulnerable to spider predation. The majority (85%) of the 374 reported incidents of frog predation were attributable to web-less hunting spiders (in particular from the superfamilies Ctenoidea and Lycosoidea) which kill frogs by injection of powerful neurotoxins. The frog-catching spiders are predominantly nocturnal with an average body length of 2.24 ± 0.12 cm (usually ≈0.1–2.7 g body mass). Altogether >200 frog species from 32 families (including several species of bitter tasting dart-poison frogs) have been documented to be hunted by >100 spider species from 22 families. Our finding that such a high diversity of spider taxa is utilizing such a high variety of frog taxa as prey is novel. The utilization of frogs as supplementary food increases the spiders' food supply (i.e., large diet breadth), and this is presumed to enhance their chance of survival. Studies from Australia and South America indicate that frogs might be a substantial component in the diet of some mygalomorph spiders (i.e., families Atracidae, Idiopidae, and Theraphosidae). Many more quantitative investigations on the natural diets of tropical spiders are needed before reliable conclusions on the importance of frogs as spider food can be drawn.
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Vertebrates are a vital ecological component of Amazon forest biodiversity. Although vertebrates are a functionally important part of various ecosystem services they continue to be threatened by anthropogenic impacts throughout the Amazon. Here we use a standardized, regularly spaced arrangement of camera traps within 25km2 to provide a baseline assessment of vertebrate species diversity in a sustainable use protected area in the eastern Brazilian Amazon. We examined seasonal differences in the per species encounter rates (number of photos per camera trap and number of cameras with photos). Generalized linear models (GLMs) were then used to examine the influence of five variables (altitude, canopy cover, basal area, distance to nearest river and distance to nearest large river) on the number of photos per species and on functional groups. GLMs were also used to examine the relationships between large predators [Jaguar (Panthera onca) and Puma (Puma concolor)] and their prey. A total of 649 independent photos of 25 species were obtained from 1,800 camera trap days (900 each during wet and dry seasons). Only ungulates and rodents showed significant seasonal differences in the number of photos per camera. The number of photos differed between seasons for only three species (Mazama americana, Dasyprocta leporina and Myoprocta acouchy) all of which were photographed more (3 to 10 fold increase) during the wet season. Mazama americana was the only species where a significant difference was found in occupancy, with more photos in more cameras during the wet season. For most groups and species variation in the number of photos per camera was only explained weakly by the GLMs (deviance explained ranging from 10.3 to 54.4%). Terrestrial birds (Crax alector, Psophia crepitans and Tinamus major) and rodents (Cuniculus paca, Dasyprocta leporina and M. acouchy) were the notable exceptions, with our GLMs significantly explaining variation in the distribution of all species (deviance explained ranging from 21.0 to 54.5%). The group and species GLMs showed some novel ecological information from this relatively pristine area. We found no association between large cats and their potential prey. We also found that rodent and bird species were more often recorded closer to streams. As hunters gain access via rivers this finding suggests that there is currently little anthropogenic impact on the species. Our findings provide a standardized baseline for comparison with other sites and with which planned management and extractive activities can be evaluated.
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Morphological, vocal and genetic studies have shown that the Madeira River and its right bank tributaries delimit populations of primates and birds. We sequenced the cytochrome b gene (approx. 950 bp) for individuals of three suboscine passerine bird species, Glyphorynchus spirurus (Furnariidae), Willisornis poecilinotus (Thamnophilidae) and Schiffornis turdina (Tityridae), on opposite banks of the Madeira River and two of its right-bank tributaries, the Aripuanã and Jiparaná rivers. Phylogenetic hypotheses (parsimony, maximum likelihood and Bayesian analysis) revealed clades that have over 3.1% genetic differentiation on opposite banks of the Madeira River for G. spirurus, W. poecilinotus and S. turdina, suggesting that this river restricts gene flow among populations of these three species. The Jiparaná and Aripuanã rivers apparently separate distinct populations of G. spirurus, the smallest species we examined, but not those of the other two heavier bodied species, W. poecilinotus and S. turdina. In G. spirurus four clades with high levels of genetic differentiation (3.2–5.5%) were found to be delimited by the three rivers evaluated, whereas in W. poecilinotus and S. turdina no genetic structure across the Jiparaná and Aripuanã rivers was detected. In general, birds that are known to show population structure across the Madeira tributaries (Glyphorynchus spirurus, Hemitriccus minor, Hypocnemis rondoni, Herpsilochmus stotzi, and Hylophylax naevius) have body masses smaller than those of both Willisornis poecilinotus and Schiffornis turdina, but some exceptions are discussed. Future studies controlling for several variables are necessary to determine the extent to which body mass is a useful predictor of genetic population structure in understory suboscine passerines.
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Natural disturbances in tropical forests modify the availability and quality of resources and alter the patterns of bird distribution. These environmental changes increase the metabolic rate and disrupt the redox balance promoting oxidative stress. This study aimed to compare the abundance of Willisornis poecilinotus between gaps and the understory of a forest with undisturbed canopy at Caxiuanã National Forest. The abundance was correlated with vegetation heights. The oxidative stress and the stress promoting factors were determined in both sites of sampling. We captured 81 specimens of W. poecilinotus. The number of captures was high in gaps. The specimens sampled at gaps showed high levels of oxidative stress. The biomarkers of oxidative stress were significantly correlated in gaps. The variability of oxidative stress and oxidative damage were explained only by site of sampling. These results suggest that gaps are stressors sites to W. poecilinotus, which probably can be due to an increase of metabolic rate to deal with new flight strategies of foraging and avoid predation KEYWORDS: antioxidants, environmental disturbances, redox balance, lipid peroxidation.
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Mist netting is a widely used technique to sample bird and bat assemblages. However, captures often decline with time because animals learn and avoid the locations of nets. This avoidance or net shyness can substantially decrease sampling efficiency. We quantified the day-to-day decline in captures of Amazonian birds and bats with mist nets set at the same location for four consecutive days. We also evaluated how net avoidance influences the efficiency of surveys under different logistic scenarios using re-sampling techniques. Net avoidance caused substantial declines in bird and bat captures, although more accentuated in the latter. Most of the decline occurred between the first and second days of netting: 28% in birds and 47% in bats. Captures of commoner species were more affected. The numbers of species detected also declined. Moving nets daily to minimize the avoidance effect increased captures by 30% in birds and 70% in bats. However, moving the location of nets may cause a reduction in netting time and captures. When moving the nets caused the loss of one netting day it was no longer advantageous to move the nets frequently. In bird surveys that could even decrease the number of individuals captured and species detected. Net avoidance can greatly affect sampling efficiency but adjustments in survey design can minimize this. Whenever nets can be moved without losing netting time and the objective is to capture many individuals, they should be moved daily. If the main objective is to survey species present then nets should still be moved for bats, but not for birds. However, if relocating nets causes a significant loss of netting time, moving them to reduce effects of shyness will not improve sampling efficiency in either group. Overall, our findings can improve the design of mist netting sampling strategies in other tropical areas.
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Acknowledgments: The late L. Richard Mewaldt was the first among,equals in setting high standards and maintenance of accurate records. His contributions are detailed by Ralph (1992). We take great pleasure in dedicating this handbook,to him. This handbook,is a direct outgrowth,of the landbird program,started more than 25 years ago at the Point Reyes Bird Observatory to monitor landbird populations in coastal California, and much of this handbook is the result of the methods developed and adapted there. Over this period, many people contributed to the development,of this landbird monitoring program. The handbook benefitted greatly from discussions and correspondence by Bruce Bingham, Grant Ballard, Danny Bystrak, Barbara Carlson, Brenda Dale, Sam Droege, John Faaborg, Kevin J. Gutzwiller, Denise Hardesty, Kimberly Hollinger, Bill Howe, David W. Johnston, Stephanie Jones, Cherry Keller, Kathy Klimkiewicz, Rolf R. Koford, Karin Kozie, Borja Milá, Sherri Miller, Michael Morrison, Barry
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Recently, a significant number of studies on neotropical forest bird communities have focused on factors influencing their richness, abundance, and habitat selection. However, few of them have considered populations or individual species, and how habitat structure affects their distribution and abundance. In this study, we investigated how the combined effects of some forest structure components affect the occurrence and abundance of a resident bird species, the scale-backed antbird Hylophylax poecilinotus (Cabanis, 1847). We tested the null hypothesis of no difference between the variation in forest structure components at locations where birds occurred and at locations where they did not. In a pristine Terra Firme forest at the Ducke Reserve, Manaus, we recorded bird occurrence and abundance using mist nets in 56 transects (1 km long each) within a 9 x 9 km trail grid covering 6400 ha. Also in the same 56 transects, we set 50 x 50 m plots and recorded the following seven components of forest structure and landscape: 1) canopy opening, 2) leaf litter, 3) tree abundance, 4) logs, 5) snags, 6) streams, and 7) elevation. We evaluated their effects on avian occurrence and abundance by using models of Multiple Logistic Regression (for bird occurrence) and Multiple Linear Regression (for bird abundance). The results suggested that H. poecilinotus occurred significantly more often in lowland areas, in areas located farther away from streams, and in areas bearing thicker leaf litter. Hylophylax poecilinotus was also more abundant in lowland areas and in areas located further away from streams. Overall, the results indicated that environmental heterogeneity produced by variation in forest structure components affects habitat use by this bird species in the Amazon forest.
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Resumo: Predação de Todirostrum cinereum (Tyrannidae) pela aranha-de-jardim Nephilengys cruentata (Aranae, Nephilidae). Relatamos a predação de um ferreirinho‑relógio (Todirostrum cinereum) pela aranha Nephilengys cruentata. Embora a predação de vertebrados por artrópodes esteja bem documentada na literatura, aranhas tecedoras de teias raramente estão envolvidas em eventos desse tipo. A nossa observação adiciona um importante exemplo de predação de ave por artrópode e reabre a discussão sobre o aproveitamento de presas de grande porte por aranhas da família Nephilidae. PalavRas-Chave: Todirostrum cinereum, Nephilengys, Predação, Nephilidae, ferreirinho‑relógio.
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1. The capture of birds using mist nets is a widely utilized technique for monitoring avian populations. While the method is assumed to be safe, very few studies have addressed how frequently injuries and mortalities occur and the associated risks have not been formally evaluated. 2. We quantified the rates of mortality and injury at 22 banding organizations in the United States and Canada and used capture data from five organizations to determine what kinds of incidents occur most frequently. Analyses focused on passerines and near-passerines, but other groups were included. We evaluated whether body mass, age, sex, mist net mesh size, month and time of day or frequency of capture are related to the risk or type of incident. We also compared the recapture histories over time between birds that were injured and those that were never injured for 16 species. 3. The average rate of injury was 0·59%, while mortality was 0·23%. Birds captured frequently were less at risk to incident. Body mass was positively correlated with incident and larger birds were at greater risk to predation, leg injuries, broken legs, internal bleeding and cuts, while smaller birds were more prone to stress, tangling-related injuries and wing strain. Rates of incident varied among species, with some at greater risk than others. We found no evidence for increased mortality over time of injured birds compared with uninjured birds. 4. We provide the first comprehensive evaluation of the risks associated with mist netting. Our results indicate that (1) injury and mortality rates below one percent can be achieved during mist netting and (2) injured birds are likely to survive in comparable numbers to uninjured birds after release. While overall risks are low, this study identified vulnerable species and traits that may increase a bird’s susceptibility to incident that should be considered in banding protocols aimed at minimizing injury and mortality. Projects using mist nets should monitor their performance and compare their results to those of other organizations.
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Ecosystem services are the benefits obtained from the environment that increase human well-being. Economic valuation is conducted by measuring the human welfare gains or losses that result from changes in the provision of ecosystem services. Bats have long been postulated to play important roles in arthropod suppression, seed dispersal, and pollination; however, only recently have these ecosystem services begun to be thoroughly evaluated. Here, we review the available literature on the ecological and economic impact of ecosystem services provided by bats. We describe dietary preferences, foraging behaviors, adaptations, and phylogenetic histories of insectivorous, frugivorous, and nectarivorous bats worldwide in the context of their respective ecosystem services. For each trophic ensemble, we discuss the consequences of these ecological interactions on both natural and agricultural systems. Throughout this review, we highlight the research needed to fully determine the ecosystem services in question. Finally, we provide a comprehensive overview of economic valuation of ecosystem services. Unfortunately, few studies estimating the economic value of ecosystem services provided by bats have been conducted to date; however, we outline a framework that could be used in future studies to more fully address this question. Consumptive goods provided by bats, such as food and guano, are often exchanged in markets where the market price indicates an economic value. Nonmarket valuation methods can be used to estimate the economic value of nonconsumptive services, including inputs to agricultural production and recreational activities. Information on the ecological and economic value of ecosystem services provided by bats can be used to inform decisions regarding where and when to protect or restore bat populations and associated habitats, as well as to improve public perception of bats.
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The composition and frequency of occurrence of mixed flocks among foraging insectivorous birds were compared between several tropical forests from South America to the Indian Ocean and Southeast Asia, and related to forest structure, foraging behaviour and abundance of predators (diurnal raptors), to investigate relationships between flocking behaviour and antipredator defence. Foliage gleaners, the most conspicuous and least vigilant foragers, were usually the most abundant flock members and the birds with the highest flocking propensity. In contrast, species foraging low above ground or in dense vegetation were the least likely to join flocks. Flocking propensity of all insectivores pooled, or of gleaners alone, generally declined from primary lowland forest to open (semi-deciduous), disturbed (logging gaps), managed or montane forest (broken canopy), i.e. when predator detectability was likely to increase. There was also a significant positive correlation between bird-hunting raptor diversity or abundance and flocking rates of foliage gleaners or all insectivores. The results supported the hypothesis that foraging birds most vulnerable to predators were most likely to form mixed species flocks and that flocking tendency decreased when vegetation structure became more protective and/or when predator pressure became lower.
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Results of queries through public avian list-servers and a thorough literature search formed a data base to synthesize patterns of birds trapped in spider webs. Sixty-nine cases of birds, representing 54 species in 23 families, were reported trapped in webs. Hummingbirds were the most diverse family (9 species) and had the most cases of entrapment (n = 20). Archilochus colubris represented the species with the most cases of entrapment (n = 6). Mean mass and wing chord length of all species trapped were 11 g and 61 mm, respectively. Eighty-seven percent of all individuals had mass < 15 g and 88% had a wing chord <90 mm. Phaethornis longuemareus and Mellisuga minima represented the smallest species (mass = 2 g, wing chord = 37 mm), and Streptopelia senegalensis was the largest (mass = 80 g, wing chord = 138 mm). Thirty cases of birds were entrapped without human intervention: 22 died and eight not wrapped in silk freed themselves. Those wrapped in silk invariably died unless freed by a human observer. One-half of all reported spider webs were of the genus Nephila, and all were orb weavers except for a single Latrodectus. Nephila clavipes entrapped nine species representing 14 cases, ranging from Mellisuga minima (mass = 2 g, wing chord = 37 mm) to Catharus ustulatus (mass = 23 g, wing chord = 93 mm). Patterns, causes, and consequences of birds entrapped in spider webs are discussed, including orb weavers as opportunistic predators of birds trapped in webs, and spider webs as a natural environmental hazard to birds.
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Foraging activity of insectivorous bats was studied from April through October in central Iowa. Temporal activity was quantified by recording capture times throughout feeding periods, and spatial patterns were examined by measuring the abundance and diversity of species in three contrasting habitats. Six species, Myotis lucifugus, Myotis keenii, Lasionycteris noctimgans, Eptesicus fuscus, Lasiurus borealis, and Lasiurus cinereus, were characterized by initial periods of foraging occurring within 5 hours after sunset. Myotis keenii and L. noctivagans had distinct secondary periods of activity, but other species showed only minor secondary periods, or complete cessation of activity, following the initial foraging period. The modes of initial and secondary activity of L. noctivagans, L. borealis and L. cinereus showed almost complete displacement and corresponded to peak periods of nocturnal insect activity, suggesting a mechanism by which some insectivorous bats may partition environmental resources. Those species showing overlap in temporal foraging (M. keenii and L. noctivagans on the one hand, and M. lucifugus, E. fuscus, and L. borealis on the other) may have evolved spatial strategies to reduce competition for resources. Intraspecific foraging patterns of three species examined may reflect resource partitioning or, alternatively, secondary foraging activity owing to different energy demands of young and lactating females.
Predation of mist net birds and an investigation of a solution
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Churchwell R, Barton G. 2006. Predation of mist net birds and an investigation of a solution. North American Bird Bander. 31:115-120.
Natural gaps associated with oxidative stress in Willisornis poecilinotus (Aves: Thamnophilidae) in a tropical forest
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Mestre LAM, Rechetelo J, Cochrane MA, Barlow J. 2011. Avifaunal inventory of a Southern Amazonian transitional forest site: the São Luiz farm, Mato Grosso, Brazil. Bol Mus Para Emílio Goeldi Cienc Hum. 6:147-161.
Ornitologia Brasileira. Rio de Janeiro (Brazil): Editora Nova Fronteira
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