Register of predation upon species of reptiles by Guira guira ( Aves : Cuculidae ) Registro de predação de espécies de répteis por Guira guira ( Aves :

Although we have a good understanding of how predation can influence community structure, we still have little information about how predation by visually oriented birds can be a significant source of mortality for reptiles. We observed adults of Guira guira feeding their offspring with four different species of reptiles, namely Amphisbaena vermicularis, Copeoglossum nigropunctatum, Iguana iguana and Tropidurus torquatus. It is the first report of G. guira predation on A. vermicularis and C. nigropunctatum. Although G. guira has been recognized as insectivorous, we believe that predation of small cryptozoic reptiles is a common event during bird breeding season.

Information on the natural history of cryptozoic and fossorial reptile species are meagre, mainly in the Neotropics.The literature about reptile's behaviour and their predators is surprisingly large, although much attention has been paid to arboreal or terrestrial-heliotherm species (e.g.Vitt et al., 2008).Because of secretive behavior, amphisbaenids and skinks are seldom observed and little is known about their distribution, behavior and predators associated (Coli and Zamboni, 1999;Vitt, 1991).However, birds seem to constantly prey on reptiles (Poulin et al., 2001), and secretive behaviour should not be a problem for feeding habit of many bird species.Predation is frequently invoked as potential driver for the evolution of reproductive modes and behaviour associated with basking, for amphibians and reptiles (Downes and Hoefer, 2004;Haddad and Prado, 2005).Furthermore, information about predator-prey is important for understanding of community dynamics and structure (Werner and Peacor 2003).In floodplains, reptiles are a group of remarkable abundance, despite the low detection rates (Junk et al., 2006;Willson et al., 2010).Pantanal ecoregion is a large lowland alluvial plain in the centre of South America (Junk et al., 2006), with more than 130 species of reptiles currently known (Strüssmann et al., 2011).Unfortunately, information about predators is lacking for many species of Pantanal herpetofauna.
Amphisbaena vermicularis is a fossorial species found in most of South America, including lowland rainforest, Cerrado, Caatinga, and seasonally flooded areas of the Pantanal (Gans, 2005).Copeoglossum nigropunctatum is a small skink that lives on tree trunks and large limbs as well as in leaf litter.This species is widely distributed in the Amazon forest, Pantanal, Cerrado, and parts of the Atlantic forest of Brazil (Vitt et al., 2008).Iguana iguana is a primarily arboreal species, distributed from Mexico to Central Brazil and Paraguay (Vitt et al., 2008), while T. torquatus is a scansorial species, ocurring in open areas of South America, east of Andes (Rodrigues, 1987).
All observations presented in this paper were made in the SESC-Pantanal Natural Heritage Private Reserve, lo-    cated in the floodplain of the Cuiabá River, Mato Grosso, Brazil (16°42'25"S, 56°28'48"W, WSG 84, 121 m above sea level).All events observed here correspond to individuals of the same flock feeding their offspring with reptiles of different behaviours and habitat use.
On 7 December 2015, at around 9h40 a.m., we observed an adult of G. guira holding a recently killed C. nigropunctatum (Figure 1).Then, the specimen of G. guira flew towards a bamboo tree and feed an offspring with the skink.The offspring cocked its head back and swallowed all but the tip of tail.A few moments after, the bird finished swallowing the skink.When we were observing feeding adults, an offspring dropped another dead C. nigropunctatum.Closer inspection revealed puncture marks, one each through the right shoulder region and through the nape (Figure 2).During the same morning, another predation event was registered at 10:40 a.m. that was practically identical to the previous event.An adult of G. guira was holding an individual of A. vermicularis in its beak (Figure 3).Small motions of the body of amphisbaenian indicated that it was still alive.The specimen of G. guira dropped the amphisbaenian at its feet and picked at it several times before flying towards the same bamboo tree.Again, an offspring swallowed the reptile whole.
Besides these registered events, we also observed G. guira preying on two other lizard species on the afternoon of the same day, around 2h00 p.m., namely a juvenile of I. iguana (Figure 4) and a juvenile of T. torquatus.Both lizards were caught by head and carried to the offspring.It is already known that G. guira feeds on these both lizard species (Koski and Merçon, 2015;Coutinho et al., 2014), but to our knowledge, this is the first report of predation on A. vermicularis and C. nigropunctatum by G. guira.Moreover, reports of G. guira offspring feeding on reptiles are uncommon (Macedo, 1994).
Although small vertebrates are occasional preys of G.guira, breeding birds are known to feed larger prey items to their offspring than those that they consume themselves (Arbeiter et al., 2014).In this sense, we posit that small reptiles may constitute an important food item to G. guira offspring.An interesting feature of these events was that lizards suffered injuries mainly in the head and without tail loss.We were able to find registers of nine reptile species as preys of G. guira (Table 1).When the predation event was observed, most of the authors stated that prey's tail was intact and bird's behaviour was similar to observed here (prey held sideways by its neck, bird pecked repeatedly at prey's head).
Many lizard species, including species in the genera Tropidurus and Copeoglossum, avoid predation by doing a caudal autotomy strategy (Bateman and Fleming, 2009).However, such strategy could be ineffective against G. guira, because the bird seems to attack preys more frequently on the head than on other body parts.On prey's perspective, attempt predation exerts a pressure on natural selection, being killed or being forced to modify some behaviours to survive (Peacor and Werner, 2001).Predation by G.guira on reptiles seems not be related to prey's microhabitat or biome (Table 1).However, a survey on prey's availability is necessary to enlighten such view.Birds and reptiles species seems to occur in great abundance in the Pantanal (Junk et al., 2006), and there is overlap between G. guira distribution and many species of reptiles.Thus, we believe that these events are common in flooded areas of Pantanal, although they were not recorded.

Figure 1 .
Figure 1.Predation on an adult of Copeoglossum nigropunctatum by an adult of Guira guira, in the floodplain of the Cuiabá River, Mato Grosso, Brazil.

Figure 3 .
Figure 3. Predation on Amphisbaena vermicularis by an adult of Guira guira, in the floodplain of the Cuiabá River, Mato Grosso, Brazil.

Table 1 .
Reptile species registered as food items of Guira guira in South American biomes.