Notas sobre el movimiento y comportamiento acuático de algunas tortugas kinostérnidas

-Las tortugas semi–acuáticas de la familia Kinosternidae han evolucionado varias adaptaciones en respuesta a cambios ambientales desfavorables, los cuales incluyen el movimiento terrestre de larga distancia en búsqueda de refugios durante sequía, y la tolerancia a altos incrementos de salinidad acuática. Sin embargo, el comportamiento y movimiento acuático de estas tortugas ha recibido poca atención

DC Birdscape: A Program for Monitoring Neotropical Migratory Birds in Washington, DC

Urban and suburban habitats often contain a variety of Neotropical migratory birds, but are poorly sampled by programs such as the North American Breeding Bird Survey. DC Birdscape was developed to inventory and monitor birds in Washington, DC. Birds were surveyed using a systematic sample of point counts during 1993-1995. Results indicate that species richness of Neotropical migratory birds varied among land-use categories, and that maximum species richness occurred in parkland habitats. Although DC Birdscape has provided relevant information on bird distribution and species richness, it is unclear whether the information is of sufficient management interest to support its continuation as a long-term monitoring program

Strong Zonation of Benthic Communities Across a Tidal Freshwater Height Gradient

Trade-offs associated with environmental gradients generate patterns of diversity and govern community organisation in a landscape. In freshwaters, benthic community structure is driven by trade-offs along generally orthogonal gradients of habitat permanence and predation—where ephemeral systems are physiologically harsh because of drying stress, but inhabitants are less likely to be under the intense predation pressure of more permanent waterbodies. However, in tidal freshwaters, these two stressors are compounding, and the trade-offs associated with them are decoupled. 2. We investigated benthic community structure in a tidal freshwater habitat. These communities experience a suite of conditions atypical for a freshwater habitat: twice-daily drying; and high predation pressure by mobile fishes. We compared benthic communities at three tidal heights (low, mid, high) and contrasted these with nearby non-tidal freshwaters that varied in their hydrology (permanent, temporary). 3. We found that communities were more strongly differentiated in tidal freshwater habitats than between permanent and temporary inland freshwaters, which was surprising given the high interconnectedness and condensed longitudinal scale of tidal habitats. The differentiation of communities in tidal habitats was probably driven by the combined gradients of desiccation risk at low tide and intense predation by fish at high tide—a combination of pressures that are novel for the evolutionary history of the regional freshwater invertebrate fauna. 4. Our study provides evidence that environmental gradients can produce stronger patterns of community zonation than would be predicted for habitats that are spatially contiguous and have little or no dispersal limitation. These results give insight into how communities might respond if drivers of community structure are altered or reorganised from their regional or evolutionary norms

Geographic variation in social organization of Galápagos mockingbirds: ecological correlates of group territoriality and cooperative breeding

To investigate ecological influences on cooperative social organization, I studied the four allopatric species of mockingbirds ( Nesomimus spp.) endemic to the Galápagos archipelago on four islands. On three small, low and arid islands (Genovesa, Champion and Española), mockingbird territories filled all terrestrial habitat, mean group size varied from 4.5 to 14.2 adults, maximum group size ranged from seven to 24 birds, and 70–100% of groups contained more than two birds. San Cristóbal is larger and higher, and it supports a broader range of habitats. At one highland and two coastal sites on this island, mockingbirds did not hold territories in all available habitats, group size averaged 2.2 adults, only 25% of groups were larger than two, and none included more than three adults. Adults dispersed into vacant habitat to establish new territories only on San Cristóbal. Helping behavior has not yet been observed on San Cristóbal, but it occurs on the other three islands. These results support the hypothesis that social groups and cooperative breeding are maintained where limited availability of preferred habitat constrains dispersal. The mechanism relaxing habitat saturation on San Cristóbal, however, remains undetermined. Predation by introduced rats and cats may reduce survival and indirectly reduce group size; these predators are absent from Genovesa, Champion and Española. Differences in food supplies could also affect interand intra-island variation in population density. Variation in social organization among arid coastal sites on the four islands, and similarity between climatically different sites on San Cristóbal, suggest that climatic conditions are less important as determinants of dispersal and breeding. Skews in adult sex ratios also fail to account for inter-island variation in sociality. Although they live in a climatically variable environment, territorial behavior and the physical limits of suitable habitat have an overriding influence on cooperative social organization in Galápagos mockingbirds.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46894/1/265_2004_Article_BF00302932.pd

Observations of the summer birds of Tukarak Island (Belcher Islands, Nunavut), Nastapoka Islands (Nunavut), and Lac Guillaume-Delisle (northern Quebec)

In a survey of land and water birds of Tukarak and Nastapoka Islands and Lac Guillaume-Delisle in summer 2011, we recorded 22 of the 30 species known to breed on the Belcher Islands, as well as five non-breeding species, and we observed 32 species in Lac Guillaume-Delisle. In all areas surveyed, we observed a total of 43 species: 10 waterfowl, 2 gallinaceous birds, 3 loons, 2 hawks, 3 shorebirds, 1 auk, 3 gulls, 2 falcons, and 17 songbirds. In this area of Hudson Bay, a number of species reach the southern or northern limit of their breeding distribution in eastern Canada. In light of the impact that climate change may have on bird distribution in northerly latitudes, the Belcher Islands and adjacent mainland areas could be particularly useful locations for monitoring changes in the breeding range of birds

Sters dan Nutrisi

viii- 79 hal-- 21 c

Stres dan Nutrisi

viii,79 hal., 21 c