Las Aves Research Articles

Los Roques and Las Aves Archipelagos, Venezuela: A Marine Ecological and Conservation Reconnaissance of Two Little-Known Southeastern Caribbean Oceanic Archipelagos

The Los Roques and Las Aves oceanic coral reef archipelagos of Venezuela lie in a biogeographically unique and biologically diverse area of the Caribbean and possess extensive coral reefs, seagrass beds, mangroves and shallow macroalgae meadows. The geographic location of these archipelagos safeguards them from most Western Atlantic hurricane damage as well as the most severe Caribbean coral bleaching episodes. While the Aves islands remain uninhabited and are an area of low accessibility, Los Roques has been a managed national park since 1972. We here present an updated synthesis of recent research for these archipelagos as an aid to scientists and conservationists interested in these island groups for which no recent ecological reviews are available. Los Roques has been much better documented than Las Aves and is the largest coral reef marine protected area of Venezuela. It has about 1,500 inhabitants living principally from tourism and fisheries. Studies show that Los Roques possesses fish populations that suffer comparatively less fishing pressure and may serve as a rare benchmark for pristine fish communities elsewhere in the Caribbean. It has also successfully maintained its importance to seabird colonies for the last five decades, notwithstanding serious marine park funding and staffing shortages. A new baseline biological inventory for Las Aves is particulary critical considering the fragmentary information available for this archipelago. The relatively intact and resilient oceanic coral reef systems of Los Roques and Las Aves are of regionally significant conservation value and deserve much more conservation and biodiversity attention than so far accorded.

Noteworthy new records of squamate reptiles (Reptilia: Squamata) from various Venezuelan Caribbean islands, including a new addition to the herpetofauna of Venezuela

The occurrence of Gymnophthalmus lineatus in Venezuela is established for the first time based on a specimen collected on Las Aves Archipelago. We also document the first records of Phyllodactylus ventralis from Los Frailes Archipelago, Amphisbaena alba from Isla de Margarita, and report the occurrence of Thecadactylus cf. rapicauda on Las Aves Archipelago. Additionally we expand the distribution of the snake Leptophis ahaetulla on Isla de Margarita and report the third specimen known from that island. We also present information on the lepidosis and coloration for all species when pertinent.

Ecología poblacional del ratón Peromyscus mexicanus (Rodentia: Muridae) en el Parque Nacional Volcán Poás, Costa Rica

The Mexican Deer Mouse has been reported as an abundant wild mouse in Costa Rica; nevertheless, it has not been studied as well as other Peromyscus species. Thirty Sherman traps were placed on three habitats during six consecutive days of each month, from March 2002 through April 2003 in three sites of Pods Volcano National Park, Costa Rica. A total of 2 393 mice were captured. Other species such as Reithrodontomys creper, R. rodriguezi, Scotinomys teguina and Oryzomys devius (Muridae) were also captured in Tierra Fría and R. creper R. sumichrasti, S. teguina and O. devius in Potrero Grande. In Canto de las Aves we captured P. mexicanus, R. creper, R. rodriguezi and O. devius. Of the total mice collected, 34.77% were P. mexicanus. For this species, the mean monthly capture per hectare was 34 +/- 2.15 in Tierra Fría and 11 +/- 1.85 in Potrero Grande. In the third site, Canto de las Aves, only four mice were captured throughout the study. The estimated population size did not change among months in Tierra Fria, but it did in Potrero Grande. No sex ratio variation was found in any habitat. In Potrero Grande, weight averages were 43.54 +/- 3.42 g for males and 42.08 +/- 3.45 g for females. Variation in population structure among habitats was not significant. The presence of oak trees (Quercus sp.) and the high understory density could explain the stability of the population in this area.

Stopover Habitat Along the Shoreline of Northern Lake Huron, Michigan: Emergent Aquatic Insects as a Food Resource for Spring Migrating Landbirds

AbstractRecent work in Michigan's eastern Upper Peninsula suggests that terrestrial areas bordering northern Lake Huron provide important stopover habitat for spring migrating landbirds, principally because of the presence of emergent aquatic midges (Diptera: Chironomidae). Migrants were concentrated in lakeshore habitats abundant with midges during spring migration. American Redstarts (Setophaga ruticilla) and Black-throated Green Warblers (Dendroica virens) foraged and used habitat differently, depending on their distance from the lakeshore. Here, we describe results of an integrative study in which we sampled resources, quantified American Redstart foraging behavior, and estimated mass change in American Redstarts and five other common migrant landbird species to evaluate the importance of adult midges as an early season resource for spring migrants. Resource sampling and American Redstart foraging behavior suggested that more food was available in shoreline habitats than inland during spring migration. Furthermore, migrants gained mass in shoreline habitat during stopover, which supports the argument that nearshore areas provide important stopover habitat for spring migrants. Finally, resource sampling, mass change estimates, and American Redstart foraging behavior suggested that midges and spiders (Araneae: Arachnidae) provided an important early season resource for migrating landbirds. Evidence suggests that midges were responsible for elevated spider abundance at the shoreline and that birds foraged on both midges and spiders. Midges appear to play an important role in providing high-quality stopover habitat for landbirds migrating through Michigan's eastern Upper Peninsula.Hábitat de las Paradas Migratorias a lo Largo de la Costa Norte del Lago Huron, Michigan: Insectos Acuáticos Emergentes como Recurso Alimenticio para las Aves Terrestres Migratorias Durante la Primavera

Fossil Passerines From the Early Pliocene of Kansas and the Evolution of Songbirds in North America

AbstractSeven living species of passerines are identified or tentatively identified from the early Pliocene Fox Canyon locality (4.3–4.8 mya), Rexroad Formation, Meade Basin, southwestern Kansas. All seven species occur in Kansas today, primarily as winter residents or transients, and their migratory behavior may extend to the early Pliocene as well. A review of all known passerines from the Neogene of North America indicates that many modern taxa began to appear in the early Pliocene, much earlier than previously believed. This fossil evidence agrees with some mitochondrial DNA analyses for the estimated age of divergence for living species of longspurs (Calcarius lapponicus and C. mccownii), but similar estimates for the divergence of C. ornatus using cytochrome-b analyses is at least 3 my younger than indicated by the fossil evidence. The fossil songbirds, as well as other vertebrate taxa from the Meade Basin, also indicate a paleoenvironment of short-grass prairie and shrubland with wetlands and ponds nearby, similar to that found in the area today. This prairie-steppe habitat first appeared in the Meade Basin by the early Pliocene and remained relatively stable until the Pleistocene, when it periodically appeared and disappeared with climate change. High seasonal productivity associated with this habitat in the early Pliocene may have promoted migratory behavior and speciation events in songbirds during a period of relative climatic stasis.Paserinos Fósiles del Plioceno Temprano de Kansas y la Evolución de las Aves Canoras en Norte América

CAN MIGRANTS DO IT FASTER? ACCELERATED MOLT OF BAIRD'S SPARROWS AND FURTHER INSIGHTS INTO SOUTHWESTERN MOLTING GROUNDS

Abstract Using museum specimens, I document the prebasic flight-feather molt and molting grounds of Baird's Sparrow (Ammodramus bairdii). Prebasic molt can apparently be carried out to some extent during fall migration. When initiating or completing molt, most Baird's Sparrows appear to be concentrated at the northern edge of their wintering range, and well within the late-summer monsoon zone. This staging may be to make use of the monsoon zone, broadly defined, but also to avoid the heavier monsoon rains found farther south in the wintering range. During prebasic molt, adult female Baird's Sparrows replace their primaries in 27 days, whereas adult males take 46 days; the mean replacement time is 39 days when sexes are combined. This is the fastest rate yet reported for a western U.S. breeding passerine, and I hypothesize that it might be due to being released from energetic constraints imposed by additional extensive migration. ?Pueden las Aves Migratorias Hacerlo mas Rapido? Muda Acelerada en Ammodramus...