Measuring ecologically important quantities at relevant operational scales: An example using the dusky flycatcher in selectively logged forests in Idaho

Effective management of forest wildlife requires information about habitat features that can be altered by operations, if those habitat features promote reproductive success and survival, and if changes in organism density influence reproductive success and survival. Habitat selection studies often provide the first type of information, although relatively few studies examine how different selection decisions or densities of organisms influence fitness measures or measure habitat features at relevant operational scales. We examined patterns of habitat selection and estimated how habitat use, territory size, and conspecific density were associated with territory success (probability of a territory producing one or more fledglings) for the dusky flycatcher in 2002–2003 on eight study plots in managed grand fir (Abies concolor) forests in Idaho, USA. Flycatchers selected territories with greater cover of deciduous vegetation in two different height strata (1–2 and 3–4 m) and reduced cover of conifers less than 4 cm dbh compared to what was available. While flycatchers selected habitat characteristics at the territory scale, model selection results did not support any associations between vegetation features and territory success. Territory success had weak positive associations, for a given territory size, with conspecific density, although the relationship was highly variable. An interaction between territory size and density was not supported. These results are consistent with the view that avian breeding habitat selection occurs at multiple scales, and that the nest site scale may explain more of the variance in reproductive success than larger scales. Our results suggest that operational management of vegetation features, which often occurs at the stand scale, may not influence variation in critical demographic metrics. Increasing total shrub cover of commonly used plant species should benefit the dusky flycatcher, as well as other shrub-nesting forest birds, but stand-level habitat alterations alone cannot be relied upon to increase reproductive success, an important component of population change.     

Spatial organization and food habits of jaguars (Panthera onca) in a floodplain forest

For most carnivore populations, territoriality is the regulating social system ultimately determined by food abundance and/or strife. However, in some food-based territorial felid species such as the jaguar (Panthera onca), the influence of food availability on territoriality remains unclear and may be lessened because of a tendency for individuals to occur at high densities across the landscape. We examined spatial organization and use of food in a population of jaguars in the southern region of the Pantanal, Brazil (2003-04). We predicted that if territoriality plays an important role in determining jaguar population dynamics, exclusive use of territories should be observed and thereby influence prey selection patterns. We determined that home range sizes were comparable between sexes and overlapped little at the core area level. Line transect surveys revealed that large mammals comprised the bulk of available wild prey for jaguars, and scat analysis indicated that jaguars relied mostly on large mammalian prey. The most common wild species killed by jaguars were capybara (Hydrochaeris hydrochaeris) and caiman (Caiman yacare). We estimated that the wild prey base was adequate to support the jaguar population. Larger wild prey species were considerably more likely to die from predation than from other causes, and predation was more likely to occur in jaguar core areas than in areas of home range overlap. Modest cattle depredation rates had little demographic importance to the local jaguar population. We conclude that spacing patterns in the local jaguar population were likely based on exclusion through territoriality rather than food limitation.     

棕背伯劳繁殖期领域性初步研究

棕背伯劳在繁殖活动中表现出很强的领域性。本文从鸣叫、飞行、栖位占据、领域面积变化和种间关系等５个方面阐述了棕背伯劳的领域性，并讨论了繁殖期各阶段领域性的变化。首次提出了领域栖位和非领域栖位的概念与划分，并明确了领域鸣叫和领域飞行等概念。     

Management of interactions between endangered species using habitat restoration

Commonly used conservation strategies may be insufficient when deleterious interactions between co-habiting endemic species occur. The decline in the population size of the endangered Leon Springs pupfish, Cyprinodon bovinus, in Diamond Y Spring, Texas has been partially attributed to egg-predation by the endangered Pecos gambusia, Gambusia nobilis. This interaction is related to changes in habitat availability; therefore, we aim to manage the conflict via restoration of the breeding habitat. We hypothesized that altering the habitat to expand shallow breeding areas would result in a decrease in the number of gambusia preying on the eggs of spawning pupfish pairs and an increase in the number of males defending territories. In 2 years following the habitat modification, we observed resurgence in the pupfish breeding population and a decrease in egg-predation pressure around spawning pupfish pairs. Additionally, after altering the habitat, gambusia were more dispersed throughout the habitat, as the low numbers of gambusia in a territory were stable regardless of spawning or aggressive behaviors by pupfish. To our knowledge, this is the first empirical example of effective management of deleterious interactions between two endangered species by means of habitat restoration.     

Seasonal variation in home-range size, and habitat area requirement of the lesser spotted woodpecker (Dendrocopos minor) in southern Sweden

Seasonal variation in home-range size and habitat area requirement of lesser spotted woodpeckers (Dendrocopos minor) were studied by radio-tracking in southern Sweden for 6 years. Home-range size did not vary between age-groups or sexes, but varied with season and decreased successively from 742 ha in winter (n=10), 355 ha in early spring (n=15), 103 ha in late spring (n=22) to 43 ha during nesting (n=10). The home-range in late spring (i.e. the 3–5 weeks preceeding egg-laying) represents the defended breeding territory. This included on average 39 ha of forest utilised for foraging (range 31–46 ha, n=15). Since food availability in late spring has a significant influence on reproductive success, and mortality is highest in this period, we regard this as an estimate of the habitat area requirement. This estimate is valid primarily for birds in southern Sweden, but circumstantial evidence indicate that the area requirement may not be grossly different in other areas with different forest types. For conservation of lesser spotted woodpeckers, management should focus on a minimum of 40 ha of forest dominated by deciduous trees, which may be fragmented over a maximum of 200 ha.     

Habitat use and spatial behaviour of the endangered Southern river otter (Lontra provocax) in riparian habitats of Chile: Conservation implications

The spatial behaviour of 10 Southern river otters Lontra provocax was analysed using radio-tracking data collected in the Queule River, Southern Chile. The estimated otter density was 0.25 individuals km⁻¹. Females with cubs and adult otters displaying mating behaviours were the only social group recorded. Studied otters were solitary and observed behaviour patterns suggest an intrasexual territoriality. No home range overlap among males existed while an average of 33% and 87% home range overlapped among females and between sexes, respectively. In the situation of core areas, only one case of overlapping between an adult male and an adult female was observed. Average home range and core area lengths were 11.3 km and 0.9 km, respectively. Otters used rivers more frequently than expected, whereas they avoided small streams. Low intensity livestock farming, without canalization of watercourses and riparian vegetation extraction practices, seems compatible with the presence of Southern river otter populations since the spatial behaviour of the studied otters was not affected under these circumstances. Based on the present official reserve sizes and distribution within the country, and also the increase of variant anthropogenic land uses outside these areas that result with consequent habitat loss and deterioration, we strongly recommend considering the importance of spatial dimension in quantity and quality habitats in further conservation planning for the Southern river otter using an integrated catchment management.