48 Cotinga 41 Three new bird species for Cocos Island, Costa Rica, and additional observations of other vagrants Guillermo Blanco and Luis Sandoval Received 27 April 2018; final revision accepted 22 September 2018 Cotinga 41 (2019): 48–51 published online 21 June 2019 En esta nota presentamos tres nuevos registros de especies en la isla del Coco, Costa Rica: Aguja Lomiblanca Limosa haemastica, Mosquerito de Traill Empidonax traillii / Mosquerito de Charral E. alnorum y Reinita de Costados Castaños Setophaga pensylvanica. Además, presentamos nuevos registros de nueve especies accidentales en la isla. Toda la información proviene de encuentros fortuitos con las especies entre 2015 y 2016. Los tres nuevos registros aumentan la lista de las islas a 152 especies, la mayoría son registros accidentales (menos de cinco observaciones para cada especie). The avifauna of Cocos Island and surrounding seas is a combination of resident (n = 13), migratory (n = 80) and accidental species (n = 56), both terrestrial and aquatic9,19. This oceanic island is in the eastern Pacific (05°32’N 87°03’W) 495 km south-west of Cabo Blanco, Costa Rica2,7,10. Its location makes it a ‘sink hole’ for migratory bird species, especially terrestrial (e.g., warblers, tyrant-flycatchers, swallows or sparrows), which become lost during migration (September–November and March–May) to and from boreal latitudes. The majority of new bird records on the island probably occurs during migration periods3,5,10,11. Here we report three new species for Cocos Island, and present further records for nine accidental species. Methods Observations were conducted opportunistically in 2015–16 on Cocos Island by GB, and photographs were taken of all new island records. We corroborated species identifications by comparing photographs of the birds in the field with specimens at the Museo de Zoología, Universidad de Costa Rica, San José, and with the text and illustrations in Stiles & Skutch23, Garrigues & Dean8 and / or specialised monographs6,17,18,22. Species accounts Purple Gallinule Porphyrio martinica A juvenile in a grassy field on 6 July 2016 (Fig. 1). Distinguished from Azure Gallinule P. flavirostris in juvenile plumage by its reddish bill with yellow- green tip, vs. yellowish bill with green culmen24,25. The third record on the island14. American Coot Fulica americana An adult on 6 December 2016 in a grassland (Fig. 2). Separated from Common Gallinule Gallinula galeata by its white frontal shield (red in the gallinule)24,25. This is the second observation on the island and the first dated record13. Killdeer Charadrius vociferus One at a grassland on 18 November 2016 (Fig. 3) was identified by its double breast-band1,17,18. The second observation on the island, after a record in 201116. Hudsonian Godwit Limosa haemastica One on a sandy beach on 5 May 2016, together with a Willet Tringa semipalmata (Fig. 4). It was an adult male in breeding plumage, with reddish breast and belly, dark wings and grey neck with black marks (Fig. 4). Nearly unmistakable among shorebirds by plumage alone, even from its congener, Marbled Godwit L. fedoa, with which it shares a long, bicoloured and upturned bill. Rare in Costa Rica, with only two previous records: one in 1975 and one on 26 April 2014 (P. O’Donnell pers. comm.), both at the Golfo de Nicoya18,23. This is the first record for the island9. Willet Tringa semipalmata One on 5–22 May 2016 on a sandy beach at the Genio estuary, Wafer Bay (Fig. 5). Showed a grey bill with black tip, bluish-grey legs, and a black- and-white upperwing pattern. Accidental on the island, with very few reports13. Wilson’s Phalarope Phalaropus tricolor An adult in winter plumage in a grassy field on 22 May 2016 (Fig. 6). Separated from other phalaropes by its long pointed black bill, white supercilium, and plain grey cap and back. This is the second record on the island, after one in 200415. Willow / Alder Flycatcher Empidonax traillii / E. alnorum One perched on a Melastomataceae bush in a grassy area at Wafer Bay on 16 October 2015 (Fig. 7). Identification of Alder E. alnorum and Willow Flycatchers E. traillii is impossible by plumage alone, even if photographed6,8,20,23. For a reliable identification, it is necessary to examine the bird Cotinga 41 49 Three new bird species for Cocos Island, Costa Rica in the hand or hear the song, although this is rarely heard outside the breeding season8,23. The photographed individual had a brownish to olive back, white throat, brownish breast, yellowish belly and white wingbars (Fig. 7). Similar species include Acadian E. virescens (greenish back and buff wingbars), Least E. minimus (conspicuous eye-ring and short bill) and Yellow-bellied Flycatchers E. flaviventris (yellowish throat, breast and belly)8,20,23. Willow and Alder Flycatchers are abundant migrants throughout continental Costa Rica between August and November8,23; however, on Cocos Island neither had been recorded to date9. Great Crested Flycatcher Myiarchus crinitus A single perched in a Cecropia pittieri (Cecropiaceae) tree on 23 October 2015 (Fig. 8). Distinguished from other Myiarchus by sharp contrast between the brighter yellow belly and grey breast, and a broad and large bill6,8,23. This is the second observation on the island after one in 196321. Chestnut-sided Warbler Setophaga pensylvanica An adult female foraging in a vine tangle on 23 March 2016 (Fig. 9) was in breeding plumage22. Diagnostic characters included the chestnut flanks stripe and yellow crown. Similar Bay-breasted Warbler S. castanea has a dark face and buffy collar, and breeding male Blackpoll Warbler S. striata a black cap, white cheeks and yellow legs22. One of the commonest migrant warblers in continental Costa Rica, from sea level to 2500 m8,23, but this is the first record for the island9. Palm Warbler Setophaga palmarum A winter-plumaged male foraging in bushes and trees on 17 May 2016 (Fig. 10). Separated from resident Yellow Warbler S. petechia aureola by its long supercilium, long tail with yellow undertail- coverts, buffy wingbars, and reddish-speckled crown4,22. This is the third record on the island, after singles observed in 196321 and 201010. Blue Grosbeak Passerina caerulea A male on 17 October 2015 (Fig. 11). Distinguished from other blue grosbeaks or buntings by its cinnamon wingbars. This is the second observation after a male observed in 201010. Indigo Bunting Passerina cyanea A female on 24 October 2015 and two males, one on 4 May 2015 and one on 9 March 2016, at different grasslands near settlements (Fig. 12). Female recognised by faint streaks on breast, and wingbars; male by its indigo plumage and silvery bill. These observations are the third to fifth records for the island, where previously recorded in 199212 and 200811. Acknowledgements We thank César Sánchez and two anonymous reviewers for comments on the submitted version of this manuscript, and Jorge Cortés and Luciano Capelli who enabled contact between the authors. References 1. Chandler, R. (2009) Shorebirds of North America, Europe, and Asia: a photographic guide. Princeton, NJ: Princeton University Press. 2. Cortés, J. (2012) Marine biodiversity of an eastern tropical Pacific oceanic island, Isla del Coco, Costa Rica. Rev. Biol. Trop. 60(Suppl. 3): 131–185. 3. Dean, R. & Montoya, M. (2005) Ornithological observations from Cocos Island, Costa Rica (April 2005). Zeledonia 9(1): 62–69. 4. Dunn, J. & Garrett, K. (1997) A field guide to warblers of North America. Boston, NY: Houghton Mifflin. 5. Easley, K. & Montoya, M. (2006) Observaciones ornitológicas en la Isla del Coco, Costa Rica (Mayo 2006). Zeledonia 10(2): 31–41. 6. Fitzpatrick, J. W. (2004) Family Tyrannidae (tyrant-flycatchers). In: del Hoyo, J., Elliott, A. & Christie, D. A. (eds.) Handbook of the birds of the world, 9. Barcelona: Lynx Edicions. 7. Fourriére, M., Azofeifa-Solano, J. C. & Sandoval, L. (2016) Species richness and density of seabirds in Isla del Coco bays, Costa Rica, related to the occurrence of breeding colonies. Marine Orn. 44: 241–246. 8. Garrigues, R. & Dean, R. (2014) The birds of Costa Rica, a field guide. Second edn. San José: Zona Tropical Publications. 9. Garrigues, R., Araya-Salas, M., Camacho-Varela, P., Montoya, M., Obando-Calderón, G. & Ramírez-Alán, O. (2017) Aves de la Isla del Coco. Lista de especies. Comité de Especies Raras y Registros Ornitológicos Asociación Ornitológica de Costa Rica. www.listaoficialavesdecostarica. wordpress.com/isla-del-coco (accessed 2 May 2017). 10. Huertas Villalobos, J. A. & Sandoval, L. (2012) Ten new bird species for Isla del Coco, Costa Rica. Check List 8: 568–571. 11. López-Pozuelo, F. & Montoya, M. (2009) Observaciones ornitológicas en la Isla del Coco, Costa Rica. IV. Enero-Mayo 2008. Zeledonia 13(2): 55–60. 12. Lücking, A. & Lücking, R. (1993) Passerina cyanea (Passeriformes: Emberizidae), nuevo informe ornitológico para la Isla del Coco, Costa Rica. Rev. Biol. Trop. 41: 928–929. 13. Montoya, M. (2006) Las aves acuáticas de la Isla del Coco, Costa Rica (humedal de importancia Internacional de la Convención de Ramsar). Zeledonia 10(2): 42–52. 14. Montoya, M. & López-Pozuelo, F. (2007) Observaciones ornitológicas en la Isla del Coco, Costa Rica (Marzo-Agosto 2007). Zeledonia 11(2): 1–11 http://www.listaoficialavesdecostarica.wordpress.com/isla-del-coco http://www.listaoficialavesdecostarica.wordpress.com/isla-del-coco Cotinga 41 50 Three new bird species for Cocos Island, Costa Rica Figure 1. Juvenile Purple Gallinule Porphyrio martinica, Cocos Island, Costa Rica, 6 July 2016 (Guillermo Blanco) Figure 2. American Coot Fulica americana, Cocos Island, Costa Rica, 6 December 2016 (Guillermo Blanco) Figure 3. Killdeer Charadrius vociferus, Cocos Island, Costa Rica, 18 November 2016 (Guillermo Blanco) Figure 4. Adult male Hudsonian Godwit Limosa haemastica in breeding plumage, Cocos Island, Costa Rica, 5 May 2016 (Guillermo Blanco) Figure 5. Willet Tringa semipalmata (right), Cocos Island, Costa Rica, 22 May 2016 (Guillermo Blanco) Figure 6. Winter-plumaged Wilson’s Phalarope Phalaropus tricolor, Cocos Island, Costa Rica, 22 May 2016 (Guillermo Blanco) Figure 7. Willow / Alder Flycatcher Empidonax traillii / alnorum, Cocos Island, Costa Rica, 16 October 2015 (Guillermo Blanco) Figure 8. Great Crested Flycatcher Myiarchus crinitus, Cocos Island, Costa Rica, 23 October 2015 (Guillermo Blanco) Figure 9. Adult female Chestnut-sided Warbler Setophaga pensylvanica in breeding plumage, Cocos Island, Costa Rica, 23 March 2016 (Guillermo Blanco) Figure 10. Male Palm Warbler Setophaga palmarum in winter plumage, Cocos Island, Costa Rica, 17 May 2016 (Guillermo Blanco) Figure 11. Male Blue Grosbeak Passerina caerulea, Cocos Island, Costa Rica, 17 October 2015 (Guillermo Blanco) Figure 12. Female Indigo Bunting Passerina cyanea, Cocos Island, Costa Rica, 24 October 2015 (Guillermo Blanco) 3 4 5 6 1 2 97 8 1210 11 Cotinga 41 51 Three new bird species for Cocos Island, Costa Rica 15. Montoya, M. & Pascal, M. (2004) Dos nuevos registros para la avifauna de la Isla del Coco, Costa Rica. Zeledonia 8(2): 7–11. 16. Obando-Calderón, G., Chavez-Campos, J., Garrigues, R., Montoya, M., Ramírez, O. & Zook, J. (2013) Lista oficial de aves de Costa Rica, actualización 2013. Zeledonia 17(2): 44–59. 17. O’Brien, M., Crossley, R. & Karlson, K. (2006) The shorebird guide. Boston, NY: Houghton Mifflin. 18. Sandoval, L. (2013) Guía de correlimos de Costa Rica. San José: Unión de Ornitólogos de Costa Rica. 19. Sandoval, L. & Sánchez C. (2018) Lista de aves de Costa Rica: vigésima sexta actualización. San José: Unión de Ornitólogos de Costa Rica. 20. Sibley, D. A. (2000) The Sibley guide to birds. New York: Alfred A. Knopf. 21. Slud, P. (1967) The birds of Cocos Island, Costa Rica. Bull. Amer. Mus. Nat. Hist. 134: 263–295. 22. Stephenson, T. & Whittle, S. (2013) The warbler guide. Princeton, NJ: Princeton University Press. 23. Stiles, F. G. & Skutch, A. F. (1989) A guide to the birds of Costa Rica. Ithaca, NY: Cornell University Press. 24. Taylor, B. (1996) Family Rallidae (rails, gallinules and coots). In: del Hoyo, J., Elliott, A. & Sargatal, J. (eds.) Handbook of the birds of the world, 3. Barcelona: Lynx Edicions. 25. Taylor, B. & van Perlo, B (1998) Rails, a guide to the rails, crakes, gallinules and coots of the world. New Haven, CT: Yale University Press. Guillermo Blanco Oficina Isla del Coco, Antiguo Inbioparque, Santa Rosa, Santo Domingo, Heredia, Costa Rica. E-mail: guillermo.blanco@gmail.com. Luis Sandoval Escuela de Biología y Museo de Zoología, Universidad de Costa Rica, Montes de Oca, San José, Costa Rica, CP 11501-2060. E-mail: biosandoval@hotmail.com. mailto:guillermo.blanco@gmail.com mailto:biosandoval@hotmail.com