Comparación del peso de diferentes tipos de plumas entre cinco especies de aves del páramo de Chirripó, Costa Rica

Plumage weight was compared in highland and wide-range bird species (N= 18 weight samples): Sooty Robín (Tutdus nigresce/lS). Rufous-collared Sparrow (Zonotrichia cape/lSís), Volcano Junco (íunco vulcani), Slaty Flowerpiercer (Diglossa plumbea), and Volcano Hummingbird (Selasphorus flammula) caplured al the Chirripó Paramo (August 1986). Relative plumage weight was not clearly related with body weight for any feather type. The relative plumage weighl was higher ín the higland species.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Differences in web features between two sympatric Leucauge species (Araneae: Tetragnathidae) suggest a trade-off in prey capture strategy

The design of orb webs is affected by multiple abiotic (e.g., wind, available space), biotic (e.g., prey availability, predation), and species specific (e.g., spider size) factors. Thus, some features of each spider web are expected to reflect the combined effect of such factors. We compared the relationship of spider size and web inclination on the area of different sections of the orb web and other features (e.g., number or radii) between two sympatric Leucauge species (Leucauge sp., and L. argyra (Walckenaer, 1841), Tetragnathidae). Leucauge sp. was smaller and constructed smaller webs across a wider range of inclinations than L. argyra. Other features of the web, e.g., capture area, and hub area, but not the number of adhesive spiral turns and number of radii, were also larger in webs of L. argyra. The inclination was greater in webs of Leucauge sp., but the asymmetry of webs did not differ between species, though, it correlated negatively with the total area of the web of both species, as in other orb-weavers. The characteristics of each species’ web suggest that L. argyra optimizes prey interception, while Leucauge sp. optimizes stopping and retention of large prey.Universidad de Costa Rica/[111-C0-252]/UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biodiversidad y Ecología Tropical (CIBET)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Detritus camouflage in webs of Helvibis longicauda (Araneae: Theridiidae)

Adult females of Helvibis longicauda accumulated tiny pieces of vegetation in the mesh of their webs. The amount of debris accumulated was much greater in webs of spiders with either egg sacs, spiderlings or juveniles than in those of adult females without eggs or offspring. The debris possibly serves to camouflage the spider’s egg sac and offspring.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

La viuda negra en Costa Rica: Información general

La viuda café (Latrodectus geometricus) ha sido probablemente introducida a América desde la región mediterránea de África. Desde su llegada a Costa Rica, esta especie ha expandido su distribución rápidamente colonizando prácticamente todas las zonas urbanas y sub-urbanas del Valle Central, hasta una elevación de 1600 m sobre el nivel del mar. La viuda café construye telas tridimensionales en forma de maraña pegadas a las paredes, bajo puentes, bajo sillas u otros muebles e inclusive dentro de las casas. Esta especie ha llegado a ser muy abundante en el país y los encuentros con humanos son frecuentes, debido a su preferencia de hábitat. La viuda café muestra la tendencia de esconderse dentro del refugio de seda que construye en su tela con el menor disturbio (por ejemplo: caída de hojas o humanos que rocen la tela). Por lo tanto, este comportamiento evasivo y la baja toxicidad del veneno de la viuda café comparado con el veneno de otras viudas negras, reduce (pero no elimina) la probabilidad de accidentes a humanos causados por esta especie, a pesar de su gran abundancia

First description of the nest and eggs of the Sooty-faced Finch

Sooty-faced Finches (Lysurus crassirostris) occur in dense undergrowth of wet forests that border streams along the Caribbean slope of Costa Rica between 600 to 1500 m in altitude. Its distribution is from Cordillera de Tilaran in Costa Rica to eastern Panama (Slud, The birds of Costa Rica. Distribution and ecology. Bull. Amer. Mus. of Nat. Hist. 128, 1964; Stiles and Skutch, A guide to the birds of Costa Rica. Cornell Univ. Press, Ithaca, New York, 1989). On 5 May, 1993, 1 found a Sooty-faced Finch nest containing two eggs at the Reserva de San Ramdn on the Caribbean slope of Costa Rica (800 m; lO”13N ’ and 84”37W). ’ The nest was attached to a fern stem 1.5 m above the ground in primary forest. The nest was roofed and had a side entrance, the 15 X 13 cm cavity was lined with fern rootlets and bamboo leaves. A soft bulk of moss decorated with fern leaves and Selaginella surrounded the outer part of the cavity and extended, just touching the fern trunk, for 67 cm below the nest. The nest contained two short-oval shaped eggs (terminology of Harrison, Afield guide to nests, eggs and nestlings of North American birds. Collins, Toronto, Ontario, 1984) with the following dimensions and mass, respectively: 24.85 X 18.90 mm and 25.00 X 18.75 mm; and 4.5 and 4.6 g. The eggs were ivory-colored with vinaceous-pink spots (Smithe, Naturalists ’ color guide. Amer. Mus. Nat. Hist. New York, New York, 1975) covering most of the wide tip and dispersed speckles (of the same color) toward the narrow end. Embryonic development had just begun in one egg but not in the second. This is the first description of the nest and eggs of this species. The nest and eggs were deposited in the ornithology collection of the Museo National de Costa Rica.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Courtship behavior and copulation in Tengella radiata (Araneae, Tengellidae)

The first description of the courtship behavior and copulation is provided for Tengella radiata (Kulczynski 1909). The male courts the female by rocking his body and vibrating his abdomen. These behaviors seem to induce the female to move out from her retreat onto the sheet and incline her body to facilitate intromission. The female has an active role during the courtship: strumming the tunnel and sheet threads, apparently inducing the male to increase the frequency and intensity of his courtship. Palpal insertion is extremely short. The female terminates the copulation by lunging at the male.Universidad de Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

EFFECT OF BODY SIZE AND MATERNAL CARE ON CLUTCH SIZE AND EGG SIZE IN THERIDIODS

Los rasgos especie-específicos de historia de vida resultan de la interacción entre diferentes factores. En arañas el tamaño de camada y el tamaño de los huevos se espera que esten influenciados por el tamaño corporal de la madre, pero también por otros factores como la disponibilidad de recursos alimenticios, así como la energía y tiempo de cuidado maternal. En ocho teridioides el tamaño corporal de las arañas y el cuidado maternal predicen el tamaño de camada. El volúmen de huevos difiere entre las especies consideradas y en general aquellas especies con poca inversion en cuidado maternal y mayor tamaño corporal muestran huevos mas grandes.Species-specific life history traits result from the interaction among different factors. In spiders the clutch size and the size of eggs are expected to be influenced by the female body size, but also by other factors such as accessibility to food resources as well as energy and time invested in maternal care. In eight theridiods the female body size of spiders and the maternal care predict the clutch size. The volume of eggs differs among all species and in general those species with little investment in maternal care and larger body size have larger eggs.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Carrion Feeding By Spiderlings Of The Cob-Web Spider Theridion evexum(Araneae, Theridiidae)

The use of carrion to feed spiderlings has never previously been observed in spiders. Here we show that the theridiid Theridion evexum Keyserling 1884 stored dead insectan prey for up to one week prior to the emergence of spiderlings from the egg sac, and continued to feed spiderlings dead prey for six weeks until spiderlings molted to the fourth instar. Spiderlings survived and molted on an experimental diet of exclusively rotten insects.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

A new subspecies of Black and Yellow Silky Flycatcher, Phainoptila melanoxantha^

in Costa Rica. In some middle and highlands the abrupt topography delayed the complete destruction of mon-UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Birds in Coastal and Marine Environments

In Costa Rican coastal and marine environments (e.g., estuaries, mud- flats, islands, open ocean) 96 bird species have been recorded, 11% of the total avifauna in the country. This high diversity is primarily explained by the complex topography of the coasts, the large variety of habitats available for coastal and marine birds, and Isla del Coco, a volcanic island that includes a particular marine avifauna. The Pacific coast, including Isla del Coco, possesses a much higher diversity of birds (93 species) than the Caribbean coast (54 species). This difference is likely explained by higher fluctuation in tides, larger extension, and greater topographical complexity on the Pacific coast. There are only 15 coastal or marine birds that reproduce (but not exclusively) in the country. From a conservation perspective, coastal and marine birds have received little attention in Costa Rica. Consequently, contamination, caused by pesticides, sewage, and solid trash, and habitat destruction, due to the construction of tourist infrastructure, seriously threaten the coastal and marine avifauna in Costa Rica.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí