Population Declines, Viable Breeding Areas, and Management Options for Flamingos in Southern Africa

Habitat rehabilitation or intervention to prevent species declines are rarely employed in Africa. I argue that despite protection in national parks, active intervention is necessary to halt declines in southern Africa's Greater ( Phoenicopterus ruber ) and Lesser ( Phoeniconaias minor ) Flamingo populations. Flamingos are long-lived species that breed sporadically at only two localities in southern Africa: the Makgadikgadi Pans in Botswana and Etosha National Park in Namibia. Despite well-publicized breeding on Etosha Pan, flamingos have experienced only three major breeding events in 40 years. Breeding failure occurs when high evaporation rates rapidly dry the pan, and up to 100,000 flightless chicks may starve. Consequently, pairs breeding in Etosha exhibit extraordinarily low recruitment (0.040 young pair/year) and extrapolations indicate that adults can replace themselves only if they breed for 38 to 50 years and all offspring survive. Because survival of offspring from fledging to adulthood (5 years) is about 46%, this breeding lifespan rises to an unrealistic 83 years, making Etosha a nonviable breeding site. Alternative, suitable flamingo habitats in Africa are being mined for soda-ash, are damaged by pollution, or are unprotected. Accordingly, continent-wide estimates and those from southern Africa alone suggest a population decline of about 40% in both species over the last 15 years. Because Namibia regularly supports 84% of the Greater and 93% of the Lesser Flamingos in southern Africa, conservation strategies are best focused there. Simple but effective management methods, based on those employed in western Europe, could reverse these downward trends. In Etosha a small island surrounded by a water-filled depression would allow up to 4000 pairs to breed annually. The benefits of enhancing the breeding of flamingos in Etosha include research opportunities, tourism revenue, and a safe haven for two Red Data species.     

Nuptial feeding in tettigoniids male costs and the rates of fecundity increase

Summary A recent debate has centred on the importance of paternal investment for the origin and maintenance of nuptial feeding in insects. Some authors have argued that the rates of nutrient incorporation are likely to be too slow to allow a male to fertilize the eggs that he helps to produce and cannot be considered as paternal investment. Here I report the results of some experiments that show that the positive effects of nutrient donation on female reproduction for one species of spermatophylax producing tettigoniid can be realized within 24 to 48 h. Furthermore, mating was found to induce a refractory period in the female that was longer than the time taken for the incorporation of nutrients and oviposition. Thus, the nurturant male is likely to fertilize the eggs even if last-male sperm precedence is high. The cost of spermatophylax production was manifest as a 5-day recovery period between matings. Thus males and their donations are likely to be limited resources for females resulting in a reversal of the typical sex roles.     

Female choice contributes to offspring fitness in the field cricket,Gryllus bimaculatus (De Geer)

Summary Females of the field cricket, Gryllus bimaculatus, are known to mate non-randomly with respect to male size. The reproductive output of females allowed to choose their mates was compared with that of females allocated mates. Females allowed to choose their mates laid a greater proportion of their available eggs, thereby investing more heavily in reproduction. Female choice did not appear to influence hatching success, suggesting that no short term benefits are derived from non-random mating. However, the offspring of females allowed to choose their mates developed more rapidly and began their own reproductive output before those of females who had been allocated mates. Furthermore, the faster developing offspring of females who chose their mates tended to have a consistantly higher survival rate as well as a lower variance in survival (i.e. less risk of mortality) at adult eclosion. Female choice may therefore contribute to offspring fitness and thus to long term reproductive success. Females allocated large males as mates did not equal those of females allowed to choose their mates, in terms of reproductive output and offspring fitness. This suggests that females may choose their mates with regard to a mixture of characters of which male size is only one.     

Food and the deceptive acquisition of mates by polygynous male harriers

Summary Female northern harriers Circus cyaneus are polygynous, marsh-nesting raptors, whose mate choices are enigmatic. I determined the mate choice cues employed by females by correlating the order in which males were chosen with characters that 1) significantly influenced reproductive success; 2) were assessable prior to settlement; and 3) varied between breeding situations. Only nest sites and male provisioning performance met all these conditions: wet nest sites significantly (P<0.05) increased nest survival and high provisioning rates significantly (P<0.01) enhanced brood survival. The order in which females settled was strongly correlated with provisioning performance in both years (r _s -0.65, and r _s -0.84), but not with nest site quality. Females thus apperared to choose males principally on provisioning performance. Despite using the same cue, however, females choosing mated males reared only 0.28 young for every nestling raised by concurrently settling monogamous females (the lowest ratio recorded for any avian species). Extrapolation of male courtship provisioning patterns from clutch sizes and laying date indicated that females received similar proportions prior to and during egg-laying, but that males later preferentially fed females. Secondary females therefore chose mated males on the basis of a temporally changing and unreliable cue. The polyterritoriality, cooperative harems, skewed sex ratio, and sexy-son hypotheses were all inadequate in explaining polygyny in harriers. Female choice of mated males among harriers is best explained by the deceitful provisioning of food by males.     

The Ythan Project: A Case Study on Improving Catchment Management through Community Involvement

Increased participation in resource management decisions by a wide range of stakeholders has been widely advocated, and has recently been formally incorporated into the European Water Framework Directive. However, achieving such participation has generally proved to be problematical. In response to locally perceived needs, a project was set up in the Ythan catchment in northeast Scotland, to undertake catchment management actions with increased public involvement. This paper outlines the methods used to increase public participation in such actions, and some preliminary assessments of the effectiveness of these. The experience of the project and the lessons learnt, including some of the difficulties of ensuring fully representative stakeholder involvement, are discussed in relation to published criteria for public participation in resource management.     

Patterns of fluctuating asymmetry in beetle horns: an experimental examination of the honest signalling hypothesis

Recent theoretical arguments have claimed that negative relationships between the size and symmetry of secondary sexual traits are indicative of honest signalling of male quality. The patterns of fluctuating asymmetry in beetle horns have been proposed to support the honest signalling hypothesis. Here we examine three assumptions of the hypothesis, (1) that traits are costly to produce; (2) the levels of fluctuating asymmetry are indicative of stress imposed during development; and (3) that males with larger traits should have more symmetrical traits, using the horned beetle, Onthophagus taurus. Experimental manipulations of brood mass were used to manipulate horn size and asymmetry. The development of horns was found to be environmentally determined and costly in terms of delayed development and increased risk of pre-adult mortality. Decreasing resource availability increased relative horn asymmetry. However, horn height was positively related to absolute horn asymmetry. While the results do support the hypothesis that sexual selection on secondary sexual traits should increase levels of fluctuating asymmetry, they provide no support for the notion that the patterns of asymmetry honestly signal male quality. Horns are used in disputes between males and may be indicative of male parental investment. Thus, we conclude that while horn size may be an indication of male quality, the patterns of fluctuating asymmetry are not. Received: 16 December 1996 / Accepted after revision: 5 May 1997     

Heritability of a male character chosen by females of the field cricket,Gryllus bimaculatus

Summary Body size in the field cricket,Gryllus bimaculatus, contributes to fitness through its effects on competitive male mating success and female fecundity and is a character chosen by females at mating. If females are to benefit from preferentially mating with large males they must be able to pass on the advantages of large size to their offspring. The heritabilities of four aspects of body size were estimated by parent-offspring regression. All aspects were shown to have heritable genetic variation despite the fact that theory predicts characters which contribute to fitness should not be heritable. There may therefore be the potential for female choice in this species to be adaptive. Some possible mechanisms for the maintenance of heritable variation are discussed.     

Some constraints on reproduction for male bushcrickets,Requena verticalis (Orthoptera : Tettigoniidae) diet,size and parasite load

Summary Reproduction for male bushcrickets is energetically expensive. Male Requena verticalis invest 70% of their daily energy reserves in calling to attract a female and providing her with a nutritious spermatophore. Males are thereby likely to be constrained in their mating frequency. I investigated constraints on reproduction imposed by body size and the levels of a protozoan gut parasite when males were fed diets that differed in their nutritional value. Males suffered a cost of reproduction in terms of an increasing interval between matings that was independent of diet and parasitic infection. After three successive matings, males decreased the magnitude of investment in courtship feeding when fed a diet poor in protein. Furthermore, these males suffered a reduction in the number of times they were capable of mating relative to males fed a diet rich in protein. Male size constrained mating frequency on both rich and poor diets; small males were able to mate less frequently than large males. There was an interaction between the effects of diet and parasitic infection on male mating frequency. Heavily infected males mated less frequently than uninfected individuals when fed the poor diet. However, males fed the rich diet were able to overcome the constraints imposed by parasitic infection. Reproductive constraints are discussed in relation to the costs of reproduction and their effects on courtship roles.     

Variable-density groundwater flow and solute transport in heterogeneous porous media: approaches, resolutions and future challenges

In certain hydrogeological situations, fluid density variations occur because of changes in the solute or colloidal concentration, temperature, and pressure of the groundwater. These include seawater intrusion, high-level radioactive waste disposal, groundwater contamination, and geothermal energy production. When the density of the invading fluid is greater than that of the ambient one, density-driven free convection can lead to transport of heat and solutes over larger spatial scales and significantly shorter time scales than compared with diffusion alone. Beginning with the work of Lord Rayleigh in 1916, thermal and solute instabilities in homogeneous media have been studied in detail for almost a century. Recently, these theoretical and experimental studies have been applied in the study of groundwater phenomena, where the assumptions of homogeneity and isotropy rarely, if ever, apply. The critical role that heterogeneity plays in the onset as well as the growth and/or decay of convective motion is discussed by way of a review of pertinent literature and numerical simulations performed using a variable-density flow and solute transport numerical code. Different styles of heterogeneity are considered and range from continuously "trending" heterogeneity (sinusoidal and stochastic permeability distributions) to discretely fractured geologic media. Results indicate that both the onset of instabilities and their subsequent growth and decay are intimately related to the structure and variance of the permeability field. While disordered heterogeneity tends to dissipate convection through dispersive mixing, an ordered heterogeneity (e.g., sets of vertical fractures) allows instabilities to propagate at modest combinations of fracture aperture and separation distances. Despite a clearer understanding of the processes that control the onset and propagation of instabilities, resultant plume patterns and their migration rates and pathways do not appear amenable to prediction at present. The classical Rayleigh number used to predict the occurrence of instabilities fails, in most cases, when heterogeneous conditions prevail. The incorporation of key characteristics of the heterogeneous permeability field into relevant stability criteria and numerical models remains a challenge for future research.