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HotScience last updated: 19 February 2003
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Sanders, M.D.; Maloney, R.F. 2002. Causes of mortality at nests of ground-nesting birds in the Upper Waitaki Basin, New Zealand: a five-year video study. Biological Conservation 106: 225-236.
This study used video cameras to obtain definitive evidence of the causes of mortality at nests of three species of ground-nesting birds. Unlike most video studies, this study videoed sufficient nests to draw conclusions about the relative impacts of various predators. Seventy-seven lethal events were recorded at 172 nests. Cats, ferrets, and hedgehogs accounted for 43, 19, and 18% of mortality at nests. Cats were the only predator to take adult birds. Stoats, avian predators, and other causes of mortality each accounted for <4% of lethal events. The paper also reports on the duration and diurnal timing of predation.
Schauber, E.M., Kelly, D., Turchin, P., Simon, C., Lee, W.G., Allen, R.B., Payton, I.J., Wilson, P.R., Cowan, P.E. & Brockie, R.E. 2002. Synchronous and asynchronous masting by 18 New Zealand plant species: the role of temperature cues and implications for climate change. Ecology 83: 1214-1225.
This paper tests for synchrony in seed crops in 34 datasets from 18 NZ plant species from Fiordland to Wellington, in Chionochloa, Nothofagus, Phormium, Elaeocarpus, and Dacrydium. All species except rimu were highly correlated across years within and between genera. Heavy seeding years came one year after warm summers, and were also related to high values of the Southern Oscillation Index (La Nina). The synchrony is apparently not driven by selective benefits (e.g. shared seed predators) but instead by incidental sharing of the same climate cue. Global warming could alter the pattern of high seed crops, with widespread community effects.
Sedgeley, J. A. 2001. Quality of cavity micro-climate as a factor influencing maternity roost selection by a tree-dwelling bat, Chalinolobus tuberculatus, in New Zealand. Journal of Applied Ecology 38: 425–438.
Building on recent work that showed that long-tailed bats were highly selective of trees and cavities for roosting (Biological Conservation 88:261–276; J. Zoology London 249:437–446), this paper shows that these bats selected cavities on the basis of their thermoregulatory quality. Cavities used conveyed significant thermoregulatory advantages to roost occupants, especially reproductive females during the day and non-volant young, which were left alone for most of the night. Bat roosts had stable microclimates, displaying small ranges in temperature and hu-midity compared with external ambient conditions and available cavities that were not used by bats.
Sedgeley, J. A. 2001. Winter activity in the tree- roosting lesser short-tailed bat, Mystacina tuberculata, in cold-temperate climate in New Zealand. Acta Chiropterologica 3: 179–195
Unusually high levels of activity compared to other small bats in temperate forests were detected in the short-tailed bats during winter on Codfish Island. Radio-tagged bats flew on >50% of nights including those where minimum temperatures were 0 °C. Large levels of activity were recorded at roosts (max. = 1443 bats). Periods of activity were associated with feeding, social displays and changing roosts. Winter activity may not be as energetically expensive for short-tailed bats as other cold-temperate bat species. Their ability to forage on terrestrial invertebrates and to select different roost sites, allow them to be active more frequently and for longer.
Sessions, L.A. & Kelly, D. 2001. Heterogeneity in vertebrate and invertebrate herbivory and its consequences for New Zealand mistletoes. Austral Ecology 26: 571-581.
A major difference between vertebrate and invertebrate herbivores is that vertebrate damage is more unevenly distributed. Data on leaf losses by Peraxilla colensoi, P. tetrapetala and Alepis flavida at three sites show that the overall mean losses to possums and insects are similar, but possum damage is more patchy among branches within a plant, among plants, and among sites. This could mean that the unlucky plants attacked by vertebrate herbivores are more likely to die, whereas insects remove a constant small amount from all plants which may be less harmful. Possums also preferred Alepis to Peraxilla spp.
Sessions, L.A. & Kelly, D. 2002. Predator-mediated apparent competition between an introduced grass (Agrostis capillaris) and a native fern Botrychium australe (Ophioglossaceae) in New Zealand. Oikos 96: 102-109.
A 1995 wildfire burnt a population of Botrychium which had been studied since 1986. The fern survived the fire well, but from 1997 on suffered very high levels of herbivory which prevented reproduction, reduced plant size and increased mortality. Exclusion experiments identified the introduced slug Deroceras reticulatum as the culprit; the slug increased due to greater shelter from Agrostis which increased after the fire. Therefore this is an example of apparent competition: the introduced grass negatively affected the native fern by harbouring an introduced invertebrate herbivore. The future for this population of Botrychium looks bleak.
Sinclair, B.J. 2001. Biologically relevant environmental data: Macros to make the most of microclimate recordings. Cryo-Letters 22: 125-134.
Automated data loggers make it possible to gather vast quantities of environmental data, but the quantity can be overwhelming, limiting interpretation to means, rather than the biologically relevant thresholds. This paper presents macros for Microsoft Excel that calculate rates of change of a data series that has crossed a threshold; it will count the number of times a threshold is crossed (and allows for the decreasing threshold being different from the increasing threshold), and for calculating the amount of time that a threshold is exceeded. These macros are available electronically from the author bjs@sun.ac.za.
Sinclair, B.J. 2001. Field ecology of freeze tolerance: interannual variation in cooling rates, freeze-thaw and thermal stress in the microhabitat of the alpine cockroach Celatoblatta quinquemaculata. Oikos 93: 286-293.
This paper takes laboratory data on the low temperature thermal biology of an alpine cockroach, and applies it to the interpretation of field microclimate data spanning 4 years. During the 1998 El Nino winter a lack of snow cover (and therefore insulation) resulted in much more extreme winter temperatures and many more freeze thaw events. This situation is used as an analogue for predicted climate change, and suggests that an alpine zone community may be maintained at low(ish) altitudes by severe frost events in this scenario.
Sinclair, B.J. 2001. On the distribution of terrestrial invertebrates at Cape Bird, Ross Island, Antarctica. Polar Biology. 24: 394-400.
In this paper the terrestrial fauna of the Cape Bird Ice-Free Area is surveyed. Little relationship was found between the presence of macroscopic vegetation and invertebrates. This has important conservation implications, because many Antarctic protected areas are currently designated on the basis of vegetation, under the assumption that this preserves a representative terrestrial community, while this paper shows that this is not the case.
Sinclair, B.J.; Lord, J.M.; Thompson, C.M. 2001. Microhabitat selection and seasonality of alpine invertebrates. Pedobiologia 45: 107-120.
This study examined the invertebrate fauna under rock slabs in summer and winter on Rock and Pillar Range, Otago. Rock size and season were the most important determinants of species presence. Species examined in detail were the cockroach Celatoblatta quinquemaculata, alpine weta Hemideina maori, and a spider Neoramia childi. We found evidence of positive interactions between weta and cockroach independent of rock size, but negative interactions between these species and spiders. The amount of vegetation around the rock was positively associated with cockroaches but negatively with weta. Adjacent vegetation composition had no effect.
Standish, R.J.; Robertson, AW.; & Williams, P.A. 2001. The impact of an invasive weed Tradescantia fluminensis on native forest regeneration. Journal of Applied Ecology 38: 1253-1263.
A major effect of Tradescantia in forest is the suppression of seedlings. Data from two Manawatu/Horowhenua forest remnants showed that Tradescantia biomass reaches a maximum at edges and under canopy gaps. In these areas, Tradescantia biomass becomes so thick that very little light penetrates to the soil and almost all woody seedlings are suppressed. In shadier spots, the Tradescantia is not as thick, more light reaches the forest floor and more shade tolerant seedlings like kohekohe establish. These results suggest that imposing shade by establishing a subcanopy through planting may allow the natural regeneration cycle to be partly restored.
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