Predation of Birds Trapped in Mist Nets by Raptors in the Brazilian Caatinga 1 2 5 Juan Ruiz-Esparza • • Resumen: 1 3 Patricio Adriano da Rocha • La red de neb/ina es una tecnica de captura de Adauto de Souza Ribeiro4 vertebrados voladores como aves y murcielagos. Una Stephen F. Ferrari4 vez capturados e inmovilizados, los animates son 1 Graduate Program in Ecology and Conservation, vulnerables a ataques par predadores hasta su extracci6n. Ataques de animates atrapados han sido Universidade Federal de Sergipe, Avenida registrados en diferentes lugares, aunque los datos son Marechal Rondon s/n, 49.100-000 Sao poco sistematicos, tales como clasificaci6n de la Crist6vao - Sergipe, Brazil. depredaci6n estrin disponibles. Analizamos ataques 2 PR D MA , Universidade Federal de Sergipe, contra las aves capturadas en redes de neblina en la Av. Marechal Rondon s/n, 49.100-000 Caatinga y regiones aledafias en el nordeste de Brasil. Sao Crist6vao-Sergipe, Brazil. Un total de 979 aves fueron capturadas durante 6, 000 horas-red de muestreo, donde 18 (1, 8%) fueron 3 Graduate Program in Zoot gy, U n:i versidade encontradas muertas en Ia red de neblina con senates de Federal da Paraiba, Joao Pessoa-Paraiba, Brazil. Ia depredaci6n. En Ia mayoria de los casas no fue posible identificar el predador, un Gavilan de los 4 Department of Biology, Unjversidade Fed ral d Caminos (Rupomis magnirostris) fue capturado junto S r0 ipe, A venida Marechal Rondon con un Chivi Amarillento (Basileuterus flaveolus) /n 49.100-000 Sao Crist6vao- Sergipe Brazil. depredado, heridas simi/ares fueron observadas en las 5 orresponding author; e-maiJ: otras aves, sugiriendo que rapaces pudieron haber sido juanco lorad 2 1@ h tmail.com responsables par los otros ataques. Se espera que informes mas sistematicos del fen6meno, incluso ABSTRACT cuando no hay victimas, pueden ayudar a proporcionar una base de datos para Ia identificaci6n y Ia resoluci6n Mist-netting is a widely used procedure for the capture de problemas potenciales en esta tecnica de muestreo, of flying vertebrates, such as birds and bats. Once para reducir a! minima perdidas en los estudios futuros. captured and immobilized, the animals are vulnerable to attacks from predators until removed by researchers. Attacks on trapped animals have been recorded at a INTRODUCTION number of sites, although few systematic data, such as predation rates, are available. We analyzed attacks on Mist-netting is a standard procedure for the capture birds captured in mist-nets at a site in the Caatinga of birds (Ralph et al. 1996) and bats and has been scrub forests ofnortheastern Brazil. A total of979 birds used at many different sites worldwide over many were captured during 6, 000 net-hours of sampling, of decades. However, as this method immobilizes the which 18 (1. 8%) were found dead in the nets with signs specimen in an exposed position, it also poses a ofpredation. While it was not possible to identify the predator in most cases, a Roadside Hawk (Rupomis certain risk with regard to the captured animal's magnirostris) was captured together with a dead vulnerability to predation. Despite the popularity of Flavescent Warbler (Basileuterus flaveolus), with the procedure, few data are available on the rates of injuries similar to those observed on the other victims, attack or loss of captured specimens from which suggests that raptors may have been responsible predation, and it is unclear to what extent this for the majority of the attacks. It is hoped that more problem of predation may affect mist netting in systematic reports ofthe phenomenon, even when there general, and specific sites or taxonomic groups in are no victims, may help provide a database for the identification and resolution of potential problems in particular. this sampling procedure, in order to minimize losses in future studies. Jan- Mar 2012 North American Bird Bander Page 11 A number of recent studies have reported on enclave of cloud forest known locally as "brejo de predation of captured organisms during the altitude" at 09° 58' 55" S, 37° 52' 06" W (750 m). trapping of birds (Recher et al. 1985, Brooks 2000, Garske and Andrade 2004, Brown and Collier The nets were opened in morning (0500-1200 hr) 2006, Curcino et al. 2009, Sakai unpubl. field and afternoon ( 1600-21 00 hr) sessions to best notes) and bats (Brito et al. 2007, Gazarini et al. sample both diurnal and nocturnal bird species. The 2008, Novaes et al. 201 0). Identified predators nets were checked at hourly intervals throughout include reptiles, [such as the Jesus Christ Lizard each session, the maximum interval recommended (Basiliscus sp.) and the Green Parrot Snake by Ralph et al. (1996). Each captured specimen was (Leptophis ahaetulla)], mammals, [such as retrieved carefully from the net and transported in a carnivores Crab-eating Fox (Cerdocyon thous) and cloth bag for processing. The trapping was Small Indian Mongoose (Herpestes auropunctatus ), authorized by the Brazilian Environment Institute opossums, such as White-eared Opossum (Didel­ (IBAMA) through special license 15 900-1 and phis albiventris) and monkeys, the Blue Monkey followed the recommendations of the Federal Bird (Cercopithecus mitis), other birds, such as the Protection Center (CEMAVE 1994). Laughing Kookaburras (Dacelo novaeguineae) and raptors the African Goshawk (Accipiter tachiro ), RESULTS Black Goshawk (A. melanoleucus), Brown Gos­ hawk (A. fasciatus), Collared Sparrowhawk (A. During the 12 months ofthe present study, a total of cirrocephalus ), Sharp-shinned Hawk (A. striatus ), 979 birds were captured in 6,000 net-hours of White-necked Hawk (Leucopternis lacernulata ), sampling effort. These specimens represented 98 American Kestrel (Falco sparverius), Roadside species belonging to 27 families (Ruiz-Esparza Hawk (Rupornis magnirostris), Northern Pygmy­ 2010). However, 77 (7.8%) ofthe specimens were Owl (Glaucidium gnoma), and Red-chested Owlet found dead in the nets. Three-quarters of these (Glaucidium tephronotum)], and even ants (Ralph individuals (59) had died from unidentified causes, et al. 2007). However, Recher et al. (1985) and which probably included stress or hyperthermia, Brooks (2000) are the only two of these studies to given the lack of any external signs of injury. The provide reliable estimates of the relative frequency other 18 (1.8% ofthe total sample) presented clear of predation. signs of predation. The present study provides quantitative data on the Most of the 12 species that suffered predation were loss of birds to predation during mist-netting at a recorded only once (Table 1), and only one species, site in the Caatinga, the semi-arid scrubland of the Pileated Finch (Lanio pileatus), was recorded northeastern Brazil. more than once in a given month. The most striking pattern in the data is the concentration ofrecords on METHODS a single day in October, when six individuals, one third of the total for the month, were found dead, The study took place at the Serra da Guia in the including the three L. pileatus, as well as Rufous­ northwestern extreme of the Brazilian state of browed Peppershrike ( Cyclarhis gujanens is), Sergipe, between Oct 2008 and Sep 2009 (for a full Olivaceous Woodcreeper Sittasomus griseica­ description, see Ruiz-Esparza 201 0). Each month, a pillus) and Rufous-crowned Greenlet (Hylophilus standardized sample was collected, in which ten 3 x poicilotis ). While these events occurred throughout 12-m mist-nets were set at the same net lanes along the morning (0500-1200 hr) and late afternoon existing trails. The nets were opened for three days ( 1600-1700 hr), it seems possible that at least some each month at a site in the scrub vegetation are related to the behavior of a single predator, and (Caatinga proper) at 09° 58' 09" S, 37° 51' 52"W in fact, two of the L. pileatus were found almost (420 m), and for a further three days in a small simultaneously during the same net check, and the Page 12 North American Bird Bander Vol. 37 No.1 Table 1. Records of birds that suffered predation while trapped in mist nets at Serrs da Guia, Sergipe, between October 2008 and September 2009. Mean 1 Adult Body Fami~ Species Common Name Length (em) Weight (g) N Month of Mortality Columbidae Leptotila verreauxi Whne-tipped Dove 26 130 3 Nov, M Jan Thamnophilklae Thamnophilus pelzelni Planaho S~ty-Antshrike 18 18 I May Dendroco~ptidae Sittasomus griseicapillus Olivaceous Woodcreeper '14 II I October Tyrannidae Hemitriccus margaritaceiventer Pear~-vented Tody-tyrant 9 7 I February Myiarchus tyrannulus Bro\\11.-crested F~catcher 18 25 I November Tolmomyi8as flaviventris Yellow-breasted Flatbill 11 10 I January V[eonidae Cyclarhis gujanensis Rufous- browed Peppershrike 15 22 I October Hylophilus poicilotis Rufous-crowned Greenlet 10 7 I October Turdidae Turdus amourochalinus Creamy-bellied Thrush 22 53 2 Apr~ May Thraupidae Schistochlamys ruficapillus Cinnamon Tanager 18 20 I October Emberizidae Lanio pileatus Pileated Finch 12 14 3 October Parulidae Basileuterus flaveolus Flavescent Warbler 14 14 2 Nov, Jul 1 Data from the present study (see Ruiz-Esparza, 2010). C. gujanensis and S. ruficapillus were found the case ofT. amaurochalinus, given that 52 birds together in the same net. Ifthe records from this day were netted. are excluded from the analysis as a possibly anomalous occurrence, the predation rate would The exclusion of this day from the analysis as an decrease to 1.2% (n = 979 captures). outlier from the monthly data, no more than three records were collected in any given month. While Considering these same 12 records as a more the sample size is small, there is little evidence of representative sample of the phenomenon, one any systematic variation among months. In fact, the potentially meaningful pattern is the fact that the most striking monthly pattern is the lack of two largest-bodied species, White-tipped Dove predation events in the two months in which most (Leptotila verreauxi) and Creamy-bellied Thrush birds were netted; i.e., December and June (Fig.