AVIAN INVENTORY AND MONITORING REPORT LOMAS DE SIERPE ÁREA DE CONSERVACIÓN OSA PIEDRAS BLANCAS, OSA, PUNTARENAS, COSTA RICA PREPARED BY: KAREN M. LEAVELLE MSC. FOR: OSA CONSERVATION APRIL 2013 Baird’s Trogon TABLE OF CONTENTS INTRODUCTION 2 METHODS 2 STUDY AREA 2 BIRD SURVEYS 2 DISTANCE ESTIMATION 8 RESULTS 9 COMMUNITY COMPOSITION AND DENSITY 9 RESIDENT BIRD SPECIES 9 NEOTROPICAL MIGRATORY BIRD SPECIES 10 MELINA COMMUNITY COMPOSITION 14 FERN GROVE COMMUNITY COMPOSITION 15 MANAGEMENT RECOMMENDATIONS AND NEXT STEPS 16 LITERATURE CITED 18 TABLE 1: Species richness 9 TABLE 2: Cumulative list of Neotropical migratory bird species 2010-2013 11 TABLE 3: List of resident bird species 2013 11 TABLE 4: List of resident and Neotropical migratory bird species in the Melina plantation 2013 14 TABLE 5: List of resident and Neotropical migratory bird species in the Fern Grove plot 2013 16 TABLE 6: Densities 17 Appendix A: Cumulative list of resident and Neotropical migratory birds 2010-2013 19 RECOMMENDED CITATION Leavelle, K.M. 2013. Avian Inventory and Monitoring Report, Lomas de Sierpe, Área de Conservación Osa, Piedras Blancas, Costa Rica. Report prepared for Osa Conservation. p23. Washington, DC. 1 INTRODUCTION In concordance with the specific objective outlined for the development and continuance of scientific investigative activities on Osa Conservation’s Lomas de Sierpe property (Friends of the Osa and CATIE 2010), I conducted a formal avian inventory of resident and Neotropical migratory bird species from 9 March to 17 March 2013. Survey objectives were designed to assess avian community composition and estimate the density and abundance of individual target bird species of management and conservation concern in future survey years. These study objectives form part of a broader goal to determine changes in bird populations and communities over time throughout Lomas de Sierpe lands for the purposes of adaptive management and strategic planning for birds within secondary forest and restoration parcels. This formal survey builds upon the baseline avian census data obtained in December 2010 and March 2011 to assess the presence of year round resident birds and migratory birds during their overwintering period in Costa Rica. Lomas de Sierpe is host to South American migratory birds that breed in Costa Rica from January to October generally. Monitoring results for these species are also reported here. This newly established inventory and property-wide avian monitoring is congruent with management policies and is designed for annual repetition and robust statistical results for all species across all habitats represented on the Lomas de Sierpe property. METHODS STUDY AREA Finca Lomas de Sierpe (8.768272°N; -83.290756°W) is 600 hectares of secondary forest, mixed secondary with primary forest surrounding mixed plantations. The property is located approximately 6 km just southwest of the town of Chacarita (Fig 1) within the Osa Conservation Area (ACOSA). It is adjacent to the Esquinas River and Piedras Blancas National Park within the Corcovado-Piedras Blancas Biological Corridor (Friends of the Osa and CATIE 2010). Not only does Finca Lomas de Sierpe share contiguous tropical rainforest with Piedras Blancas National Park, its conservation value is extremely important due to is location next to the mangroves and riparian forest of the Esquinas River which provide important habitat for many resident and migratory bird species. Lomas de Sierpe is also located just south and east of the Térraba-Sierpe National Wetlands, an internationally recognized RAMSAR site. The property is primarily composed of ~ 532 ha of secondary forest at varying ages of forest succession, and mixed forest comprised of both secondary and primary forest trees. Approximately 26 ha is old pasture land converting to fern and woody shrub vegetation adjacent to the Rio Esquinas Approximately 40 ha is melina (Gmelina arborea), 1 ha amarillón (Terminalia amazonia) and 1.24 ha pine (Pinus caribaea) plantation. The road between Mogos and Chacarita runs in an east west direction through the property. 2 Fig 1: Study area and survey transects at Osa Conservation’s Lomas de Sierpe property adjacent to the Rio Esquinas and Piedras Blancas National Park 2013. BIRD SURVEYS I surveyed birds in 9 March to 17 March 2013 using standard point transect methodology (Buckland et al. 1993) with a total of four line transects stratified by habitat (Fig. 1). I walked each line transect slowly (5 min/25 m) observing and recording all birds seen or heard at a maximum perpendicular distance of 50 meters from the center line from the hours of 5:30am – 9:00am, the time of day when birds are most active. Only birds observed perpendicular to the observer or ahead of the observer were recorded to avoid double counting individual birds (Verner 1988; Ralph et al. 1993). I also recorded birds observed outside of transect counts for documentation (Appendix A). I did not conduct surveys during periods of heavy rain or strong wind because bird activity is suppressed and the observer's ability to detect birds is reduced under these conditions. The March time period allows for surveys of migratory birds that are still present on their overwintering grounds in Costa Rica and is a good month for auditory and visual observations of active resident birds engaged in reproductive behaviors such as singing and territoriality. 3 The following are descriptions of each transect as they appear from north to south (Fig 1). Transect 1 (500m): Melina (Gmelina arborea). This temporary transect was placed in the plantation prior to the existence of reforestation lanes (trochas). Once permanent ‘trochas’ are established, a permanent transect can be placed in this area for investigation. This plantation is primarily composed of melina with some interspersed mixed tree species. Tree diameter is small, uniform and forest complexity and structure is low (Fig 2). Though it looks similar in complexity and structure to La Suita (below), the number of tree species is reduced due to the presence of dominant Melina. Fig 2: Melina plantation, Lomas de Sierpe 2013. 4 Transect 2 (1km): La Suita. This transect is early to mid-succession secondary forest and is open and uniform in most places interspersed with areas farther away from the road that are older with larger diameter trees, mixed rainforest tree species and increased understory density (Fig 3). Overall, it is a relatively young forest with an open canopy as compared to Sendero de las Aves y Sendero del Amor. Fig 3: La Suita trail, Lomas de Sierpe 2013. 5 Transect 3 (700m): Sendero de las Aves. This transect runs from the road down towards the Rio Esquinas and is primarily old growth secondary forest mixed with primary forest patches or old growth large diameter trees. Tree diameter is mixed large and small and forest complexity and structure is high (Fig 4) providing niches at all strata of the forest for a variety of bird species. Many large diameter snags are also found here providing habitat for woodpeckers, parrots and tityras. Fig 4: Sendero de las Aves, Lomas de Sierpe 2013 6 Transect 4 (700m): Sendero del Amor. This transect runs parallel to the Sendero de las Aves and now connects with it as well. It is nearly identical to the Aves trail but runs adjacent to the Rio Esquinas (Fig 5), and is comprised of montane vegetation (Fig 6) which transitions into riparian vegetation down along the river. The change in habitats provides a rich environment for bird species diversity in this area. Fig 5: Sendero del Amor along the Rio Esquinas, Lomas de Sierpe, 2013. Fig. 6: Sendero del Amor, montane vegetation, Lomas de Sierpe, 2013. 7 Fern Grove Observation Points. The ‘Fern Grove’ term has only been used for the purposes of this report. Any official names for this area should replace this name. Due to cloud cover in the Google Earth image I have not delineated the fern area with a polygon. The two triangles shown in the map are located on the north eastern border of the ferns while the single triangle below is a southern border point. Other sides of this area were not accessible for this study. The ferns in this area are dense and have grown well over 2 meters tall in some areas restricting access and feasibility for transect counts (Fig 7). I therefor located the three observation points in order to conduct a census of birds using this particular area. As well, the ferns are intermixed with woody shrub vegetation throughout, most of which reach the height of the ferns, while a few have extended growth above the tip of the ferns providing scattered bird perches. Old pastures borders lined with trees left by ranchers are still present and cut through the fern area just as they did when the area was grazed by cattle. The outer edges are secondary forest, creeks with riparian associated vegetation (Heliconias), and fruit trees. Fig 7: Fern Grove (transitioning pasture land) adjacent to the Rio Esquinas, Lomas de Sierpe, 2013. DISTANCE ESTIMATION I used Distance estimation to estimate detection probability where objects may go undetected (Buckland et al. 1993, 2001) to increase precision in species density estimates. Four repeat surveys were conducted at each transect over the course of the sampling period. In order to obtain a usable probability estimate of species density a minimum of three repeat visits is suggested (Tyre et al. 2003, MacKenzie and Royle 2005). I used program Distance 6.0 (Thomas et al. 2009) to estimate species density (birds/ha) for species with significant numbers of detections, and the probability of detecting a species (p) from the observer to the object of interest across all sample points (See Leavelle 2012 & 2013) report for more detailed sampling information). 8 RESULTS COMMUNITY COMPOSITION AND DENSITY A combined 119 species (99 residents and 20 Neotropical migrants) representing 35 families were observed at Lomas de Sierpe in 2013 (Tables 1-3) while 152 species (131 resident and 21 Neotropical migrants) representing 38 families were observed over all sample years (Table 1 & Appendix A).