The consequences of disrupted dispersal in fragmented red-cockaded woodpecker Picoides borealis populations.

1. Habitat fragmentation may adversely affect animal populations through several mechanisms. However, little is known about how the impacts of some of these mechanisms are manifested in altered dynamics of wild populations. 2. We used a spatially explicit individual-based simulation model to examine the potential effects of disrupted dispersal due to fragmentation on the population dynamics of the endangered, co-operatively breeding, red-cockaded woodpecker Picoides borealis. 3. We simulated population dynamics as a function of population size and spatial aggregation of territories. Dispersal success (but not mortality or fecundity) was an emergent property of model runs. In the model all female and some male fledglings dispersed in straight lines in random directions, and the remaining males stayed on their natal territories as helpers and competed for breeding vacancies in their immediate neighbourhood. 4. Population trend was tied to the higher dispersal success of both males and females in larger and less fragmented populations. Helpers were more successful than dispersing males. Male breeder recruitment depended entirely on helpers when populations were small (25 or 100 territories). 5. Declining populations were characterized by high emigration rates and both failure and delay in female recruitment. The large numbers of unpaired males resulted in lowered reproductive output at the population level and in the loss of territories. Populations of 25 territories were stable when territories were highly aggregated, despite high emigration rates. These results closely match empirical observations. 6. A number of co-operatively breeding species are endangered. The unusual dispersal behaviour of helpers may make such species sensitive to habitat fragmentation but also resilient to reductions in population size when territories are aggregated. Small populations of co-operative breeders may have considerable conservation value as a source of genetic diversity

On the use of divergence statistics to make inferences about three habitats

Several coefficients, called divergences, have been suggested in the statistical literature to reflect the fact that some probability distributions are ''closer together'' than others and consequently that it may be easier to distinguish between the distributions of one pair than between those of another. When comparing three biological populations, it is often interesting to measure how two of them ''move apart'' from the third. Deals with the statistical analysis of this problem by means of bivariate divergence statistics. Provides a unified study, depicting the behaviour and relative merits of traditional divergences, by using the (h,phi), divergence family of statistics introduced by Menendez et al

Initiation and continuation of breastfeeding: theory of planned behaviour

Aims. This paper reports a study investigating new mothers' subjective norms in relation to both breast- and bottle-feeding. The influence of norms on women's infant feeding decisions and the relative influence of social referents at varying degrees of social distance were assessed.Background. Increasing breastfeeding initiation and continuation rates is a key challenge for health educators. The perceived influence of other people's views (subjective norms), including the views of women's partners and health care professionals, is an important predictor of infant feeding behaviour.Methods. Semi-structured questionnaires were administered to 203 new mothers in central and northern Scotland and followed-up by postal questionnaire at 6weeks. Infant feeding intentions, feeding behaviour at birth and follow-up, behavioural beliefs and subjective norms for both breastfeeding and bottle-feeding were assessed. The data were collected in 1998-1999.Results. Subjective norms were important determinants of initiation and continuation of breastfeeding for breast- and bottlefeeders. Breastfeeders rated close social referents as more in favour of bottle-feeding and more against breastfeeding at follow-up, whereas bottlefeeders' ratings did not change. Partner's and nurses'/midwives' views were an important influence at baseline and follow-up. Breastfeeding ‘continuers' perceived their partners as more pro-breastfeeding at 6weeks. Discontinuers perceived more overall social pressure to bottle-feed. However, sampling limitations may have led to over-representation of the views of breastfeeders at baseline and follow-up.Conclusions. Nurses and midwives have a crucial role in communicating positive views on breastfeeding to new mothers at different time points. Future interventions to promote breastfeeding could adopt a broad social approach, encouraging positive norms for existing and potential mothers and fathers, families and people in general