Notes on Breeding Birds from the Guyana Highlands with New Records from a Recent Inventory of Mount Ayanganna Christopher M
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Cotinga 38 Notes on breeding birds from the Guyana highlands with new records from a recent inventory of Mount Ayanganna Christopher M. Milensky, Mark B. Robbins, Jacob R. Saucier, Brian J. O’Shea, Aleks Radosavljevic, Tristan J. Davis and Meshach Pierre Received 11 October 2015; final revision accepted 28 April 2016 Cotinga 38 (2016): 64–78 A continuación se presentan los resultados de un nuevo estudio de la avifauna del Monte Ayanganna, que incluye cuatro nuevas especies en Guyana. Estos resultados se combinaron con los de investigaciones anteriores sobre el monte Roraima y la montaña Kopinang para esclarecer los patrones y época de reproducción en los tepuyes guyaneses. Los tepuyes de Guyana no están lo suficientemente estudiados ornitológicamente; nuestras investigaciones han sido las primeras en documentar la avifauna de estos tepuyes. En cada ubicación fueron estudiados los mismos rangos altitudinales, con alguna variación en el mes y posición. Patrones climáticos altamente variables influyen en gran medida en la vegetación de los tepuyes. Durante nuestro estudio hallamos hábitats únicos, desde bosque alto a matorrales de tepuyes, y con precipitaciones oscilando desde relativamente seco a extremadamente húmedo. En un intento de discernir patrones en los ritmos de reproducción se compararon los datos sobre las condiciones de reproducción en estas tres investigaciones. Como era de esperar, los patrones estacionales resultaron difícil de determinar salvo en unas pocas excepciones. The unique tabletop mountains of the pantepui Here, we present results from a recent avian survey region of the Guianan Shield have been the focus of of Mount Ayanganna and supplement these data scientific study, folklore, legend and casual curiosity with unpublished information from our Mount for almost two centuries. Boundary explorations in Roraima and Kopinang Mountain surveys. Because the 1800s along the borders of Venezuela, Guyana of inaccessibility, anthropogenic influence has been and Brazil led to numerous scientific discoveries and minimal at all three sites. We present complete increased awareness of the tepui flora and fauna. species lists with relative abundance, elevations While many of these early surveys originated in and breeding data for all three tepuis. the former British Guiana, most focused on Mount Roraima, the higher elevations being accessible Site description and Methods from Venezuela. Some of the early explorers, such Study area and methods for the Mount Roraima as Henry Whitely, Robert & Richard Schomburgk, and Kopinang Mountain inventories have been Frederick V. McConnell, John J. Quelch, George described previously2,14. These surveys were H. Tate, Thomas D. Carter, William H. Phelps conducted on the north-east slope of Mount Jr. and Sr., and others, contributed a wealth of Roraima at 600–1,500 m in March–April 2001 knowledge and many publications on the flora and and Kopinang Mountain, at the southern end of fauna of the pantepui region and Mount Roraima the Wokomung massif, at 700–1,400 m in July in particular13. 2004. CMM participated in all three surveys, while Guyana’s tepuis received less attention, with MBR & BJO participated in two of the three. The some never having been ornithologically explored, Mount Ayanganna survey was the only trip with due to difficulties in accessing the road-less interior. a botanist, AR, as part of the team. The number Those early explorers that did make attempts, such of field days, observers and mist-netting effort for as Henry Whitely, had only primitive maps resulting each expedition were similar, although no field in uncertainties surrounding specimen provenance. camps were established above 850 m on Kopinang. Moreover, the limited specimen material that was On Mount Ayanganna, we used an established obtained during the 19th and early 20th centuries trail that began at a mining airstrip at 700 m have a paucity of data compared to data-rich (05°18’10”N 59°50’16”W) and followed the Potaro material from the past 20 years. River through a small village before ascending the The status and distribution of the Guyana north-east slope of the mountain10. The mining tepui avifauna remain poorly known. Expeditions airstrip has been used infrequently and there are during the last two decades have provided baseline no permanent inhabitants, although miners have inventories of the Potaro Plateau, Iwokrama established camps adjacent to the Potaro River. Mountains, north slope of Mount Roraima, and Prior to our expedition, guides from the nearest Kopinang Mountain1–3,14,17. Mount Ayanganna has Patamona Amerindian communities (c.60 km to been inventoried by botanists, mycologists and the south) were contacted to clear the airstrip and herpetologists, but never by ornithologists8,10,11. a reconnaissance trip was made by CMM on 2–8 64 Cotinga 38 Notes on breeding birds from the Guyana highlands Figure 1. Map of the Pantepui region and our three study sites in Guyana. February 2014. During this time, arrangements until after 08h00), especially at the uppermost were made for 27 porters from the Patamona camp, there was considerable variation in mist-net communities to meet the main expedition party at and observational effort. On Mount Ayanganna, the airstrip on 8–10 March 2014. Avifaunal surveys mist-nets were generally opened from dawn to were made by part of the team during the initial dusk, with most observer data collected during two days while waiting for the arrival of additional morning and late afternoon walks when information members and supplies. After making an ascent concerning habitat, behaviour, breeding activity of the north-east slope, we established our first and feeding patterns were noted. Representative field camp at 1,375 m (05°22’34”N 59°58’21”W) on series of specimens were preserved as study skins, 14–22 March, followed by a mid-elevation camp skeletons and whole birds in fluid, along with on 23 March–2 April at 1,075 m (05°20’17”N frozen tissue samples. Specimens are deposited 59°56’45”W) and the airstrip area on 4–8 April. At in the Smithsonian National Museum of Natural each camp, surveys were conducted along existing History, Washington DC (USNM), the University trails using binoculars, ground-based mist-nets of Kansas Biodiversity Institute, Lawrence (KU), (15–25, 12 m in length), shotguns and digital and Centre for the Study of Biological Diversity audio-recorders. Due to heavy rain (often persisting at the University of Guyana, Georgetown (CSBD). 65 Cotinga 38 Notes on breeding birds from the Guyana highlands Audio-recordings made by MBR are archived and Therefore, relative body mass in relation to testes available online at the Macaulay Library (ML), size was considered when using testes size as a Cornell Laboratory of Ornithology. breeding indicator. Females with collapsed follicles, Mount Ayanganna (summit: 05°23’10”N enlarged and convoluted oviducts, brood patches 59°59’26”W, 2,020 m) is the easternmost tepui above or shelled / unshelled eggs in the oviduct were 2,000 m (Fig. 1). Habitat here is typical of other tall considered to be breeding, as were recently fledged tepuis in the Pakaraima Mountains. Terra firme young. Immatures with bursa of Fabricius and tropical forests in the rolling foothills quickly give partially pneumatised skulls were not considered way to montane vegetation and cloud forests on to be breeding as they can retain these characters the higher, wetter sandstone escarpments leading for several months6. For example, more than half to the summit, while the summit itself harbours of Slate-crowned Antpitta Grallaricula nana 10 a distinct ‘high-tepui’ flora . The lower slopes and specimens had bursas and partially pneumatised uplands are marked by higher diversity but lower skulls in various states of advancement, but none endemism compared to the plant communities of of the adults had enlarged gonads. We converted 4 the summits . These lower forests are dominated breeding data to continuous numerical values, by plant families such as Fabaceae, Sapotaceae, which permitted us to rate breeding status from Clusiaceae and Lecythidaceae; Melastomataceae non-breeding to breeding while also accounting for and Rubiaceae comprise a major component of intermediate cases. These values were averaged, 8,10,13 the understorey . Beginning at c.1,000 m the analysed and are discussed in Results. It should be canopy becomes lower in stature and epiphytic emphasised that our surveys only covered a short plants more prevalent. Clusia, Protium and Inga timeframe and that some species were represented are more frequent, and large stands of Euterpe by only 1–2 specimens; therefore, our assessment of (spiny palms) and Rapataea dominate on wetter breeding should be considered incomplete. We used ground. Above 1,300 m the vegetation is more behavioural observations (e.g. persistent singing typical of a true cloud forest, i.e. short, gnarled trees and / or individuals carrying nesting material) with coriaceous leaves and a high concentration of to supplement specimen data as an indication of vascular and nonvascular epiphytes. Bonnetia, breeding. Podocarpus, Weinmannia, Schefflera and Cyrilla increase in frequency with elevation in the forested areas, while Stenopadus, Byrsonima, Cyperaceae, Results and Discussion The Mount Ayanganna inventory documented Drosera and Lycopodiaceae are common in open and four new species for Guyana: Tepui Tinamou boggy places. The plant families Melastomataceae Crypturellus ptaritepui, Band-tailed Pigeon and Rubiaceae are common throughout. These Patagioenas fasciata, Striped Woodhaunter cloud forests eventually give way to what is Automolus subulatus known as ‘tepui scrub’ at c.1,500 m—a nearly and Golden-rumped Euphonia impenetrable tangle of small trees and woody Euphonia cyanocephala (see below). Species shrubs <2 m tall growing in an accumulated peat encountered at lower elevations (c.700–900m) were layer interspersed by herbaceous meadows2. While typical of lowland and foothill avifaunas elsewhere there is significant plant diversity in this region, in Guyana, although several species characteristic during our expedition the forests were relatively of those zones were rare or absent.