Treesearch

Avian parents influence the onset of development, hatching synchrony, and likelihood of brood reduction through the onset of incubation. Studies testing adaptive functions of brood reduction assume that eggs are protected by their shells and waiting for parents to initiate incubation in a manner that creates optimal hatching patterns, but the viability of early laid eggs may diminish over time due to putative effects of ambient temperature. We tested effects of exposure to ambient temperature on the viability of unincubated bird eggs using an altitudinal climate gradient in Puerto Rico:...

Massive upstream migrations of neritid snails (Neritidae: Gastropoda) occur in tropical and subtropical streams worldwide, but their seasonality and proximate causes are unknown. We monitored massive upstream migrations of Neritina virginea for 99 weeks, and conducted a detailed study of snail density, size, and hydraulic descriptors in lower Río Mameyes, northeastern Puerto Rico. The study assessed the 1) timing and seasonality of upstream migration, 2) size composition of migratory aggregations, 3) patterns of habitat use, and 4) role of floods on upstream migration. Massive upstream...

Total aboveground live tree biomass in Puerto Rican lower montane wet, subtropical wet, subtropical moist and subtropical dry forests was estimated using data from two forest inventories and published regression equations. Multiple potentially-applicable published biomass models existed for some forested life zones, and their estimates tended to diverge with increasing tree diameter at breast height. Inventoried forests showed structural characteristics typical of secondary tropical forests and stand successional trends of increasing stem density from initial reversion to young closed...

Abstract.—Using evidence from individually-marked birds and radio-telemetry, we studied daily and seasonal habitat use of Northern Waterthrushes (Seiurus novaboracensis) in Puerto Rico during the nonbreeding season from 1999 to 2001. Our study was conducted in mangrove habitats along the southwest and east coasts and near ponds and washes in mesquite savanna in the southwest. Of 29 radio-equipped birds we found a dominant pattern of overnight roosting (87.8% of radioed birds) in coastal red mangroves (Rhizophora mangle), regardless of the habitat used for daytime feeding. Birds left...

We studied winter avian distribution in three representative pine-dominated habitats and three broadleaf habitats in an area recently designated as a National Park on Andros Island, The Bahamas, 1-23 February 2002. During 180 five-minute point counts, 1731 individuals were detected (1427 permanent residents and 304 winter residents) representing 51 species (29 permanent and 22 winter residents). Wood warblers (Family Parulidae) comprised the majority (81%) of winter residents. Total number of species and individuals (both winter and permanent residents) were generally highest in moderately...

We studied winter avian distribution and relative abundance in six common terrestrial broadleaf habitats, selected on a continuum of disturbance from recently disturbed (abandoned plantation) to mature vegetation (tall coppice), on the island of Eleuthera, The Bahamas. During 158-point counts conducted 22 January—10 March 2003, 1357 individuals were detected, comprising 33 species. Winter residents comprised 47% of species detected and 20% (248/1357) of individuals. The abundance of both permanent and winter residents was highest in taller, more mature vegetation (short and tall coppice)...

Earthworms are recognized to play an important role in the decomposition of organic materials. To test the use of earthworms as an indicator of plant litter decomposition, we examined the abundance and biomass of earthworms in relation to plant litter decomposition in a tropical wet forest of Puerto Rico. We collected earthworms at 0–0.1m and 0.1–0.25m soil depths from upland and riparian sites that represent the natural variation in soils and decomposition rates within the forest. Earthworms were hand-sorted and weighed for both fresh and dry biomass. Earthworms were dominated by the...

Big-leaf mahogany (Swietenia macrophylla) is a valuable neotropical timber species whose seedling survival and growth dynamics in natural forests are poorly understood. To document regeneration dynamics of mahogany in seasonal transitional evergreen forests of southeast Pará, Brazil, we followed naturally established seedlings in the forest understory and in experimental canopy gaps. We found that only 1–2% of seedlings in the forest understory survived 8 years after germination; mean height growth was approximately 4 cm year-1 of height over this period, confirming mahogany’s classificatio...

Avian eggshells harbour microbes shortly after laying, and under appropriate ambient conditions they can multiply rapidly, penetrate through shell pores, infect egg contents and cause embryo mortality. We experimentally examined how incubation affects bacterial processes on the eggshells of pearl-eyed thrashers Margarops fuscatus nesting in tropical montane and lowland forests in Puerto Rico. Bacteria and fungi grew rapidly on shells of newly laid, unincubated eggs exposed to ambient conditions, but declined to low levels on shells of eggs incubated by thrashers. Divergence in bacterial...

Nothofagus pumilio (lenga) forests form monocultures from sea level to timberline in Tierra de Fuego, Argentina. Past studies suggested that the life form change from erect forest to krummholz had advantages to forest function. Aboveground net primary productivity (NPP) and organic matter production per unit leaf area and growing season day were higher in krummholz than in adjacent short erect forests at lower elevation.We compared tall erect, short erect, and krummholz lenga stands in terms of the concentration, accumulation, fluxes, turnover, and use-efficiency of nutrients (N, P, K, Ca,...