In central Africa, commercial poaching and local village hunting are still two major issues that logging companies must address through the implementation of effective management plans in order to ...certify their concessions. However, current problems in developing suitable hunting management schemes for dense tropical forests arise from (1) the difficulty associated with setting quotas which take into account indiscriminate local hunting practices (e.g. snare trapping) and the ill-defined modes of resource appropriation by local populations, (2) the difficulty associated with evaluating the effect of illegal hunting, i.e. poaching, and (3) the relative complexity of the main available model. To overcome this, we propose to develop alternative management models where village hunting is planned along the same lines as existing logging operation models, through the implementation of a system of spatio-temporal rotation of hunting areas. In practice, the logging concession, initially divided into annual logging areas, is divided into similar annual hunting areas (AHAs), which are opened to hunting during the year preceding the logging operations. A depletion of the wildlife stock is expected within the annually opened hunting areas, but the model assumes a progressive re-colonization of the depleted AHA in subsequent years from neighbouring ones. In this paper, an empirical model of such a controlled hunting system employing spatio-temporal rotation of hunting areas is tested within a Forestry Management Unit (FMU) covering 47,585 ha in the Dja region, in south-east Cameroon. The model, based on large forest areas, seems particularly well adapted to Cameroon's dense forests because it fits within the existing legal framework of Community-Managed Zones of Hunting Interest (CMZHI) and is aligned with current logging concession operations. Preliminary results suggest that sustainable hunting can be achieved in the FMU, provided a management scheme of AHAs is strictly enforced through effective stakeholder commitment.
Despite a high degree of endemism (c. 30%) and the existence of some serious threats, the avifauna of the Comoro Islands remains poorly studied. This paper reports on a bird census conducted on Grand ...Comoro (Ngazidja) in the afromontane forest ecosystem of Mt Karthala. Point counts were conducted over a 3-month period (March–May 1999) in different habitat types, along an altitudinal gradient ranging from completely degraded forest plantations (400–800 m elevation) to montane forest with modified understory (800–1200 m elevation) and intact cloud forest (1200–1800 m elevation) replaced by giant heathland at highest altitudes (>1800 m elevation). I tested whether or not species diversity, bird assemblages and level of endemism differed between habitat types. Furthermore, I investigated whether temporal changes had occurred since a previous census conducted in 1985–1989. Overall, 37 species were contacted during the census. No evidence of temporal changes in species diversity indices was detected during the short time interval separating both studies (10–15 years). However, the analysis could not account for the impact of increased areas of degraded forest on specific population sizes. Mean species richness and Shannon–Wiener index per point differed with respect to habitat type, being much lower in giant heathland. Mean species richness per point differed also with respect to factor “slope”, being highest in south-western montane forest with modified understory and cloud forest. An altitudinal endemism gradient was apparent with only three endemic species characteristic of low- to mid-altitude degraded habitats, while the bulk of endemic species was restricted to intact patches of primary cloud forest (six species) and giant heathland above 1800 m (one species). These findings, combined with the recent reports on ongoing levels of forest degradation and encroachment by local human populations, suggest that the survival of endemic forest species is dependent on the designation of a nationally-supported conservation area on Mt Karthala.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Both intrinsic and extrinsic factors recorded at individual nests can predict offspring fitness and survival but few studies have examined these effects in the tropics. We recorded nestling survival, ...post‐fledging survival and age at first return of
R
oseate
T
erns breeding at
A
ride
I
sland,
S
eychelles, over a 12‐year period (1998–2009). Nest data recorded at the egg, nestling and fledging stages were collected during six breeding seasons (1998, 2001–2005) and a capture‐mark‐recapture dataset of six cohorts of fledglings was obtained from 2001–2009. Logistic regression models were used to assess the predictive effect of reproductive variables on fledging success, while multistate capture‐mark‐recapture models were used to estimate post‐fledging survival and return–recruitment probabilities to the natal site. Nestling survival probability increased with earliness of laying and was negatively affected by tick infestation during the growth period (0–23 days). Fledging probability was also positively related to chick body condition, whereas other pre‐fledging reproductive parameters such as clutch size and egg size were not influential. A multistate modelling of age‐specific survival and return–recruitment (transition) rates found that first‐year survival differed between cohorts and was also negatively affected by tick infestation. Annual survival stabilized from age 2 onwards at 0.83 ± 0.02. Transition rates were positively related to body condition at fledging, with heavier individuals returning for the first time to the natal colony at a younger age compared with lighter individuals. These results highlight the importance of local conditions encountered by tropical seabirds during the breeding season in shaping demographic parameters.
Studies of regeneration in African rain forests suggest that without silvicultural treatments, natural succession in logging gaps may not result in the establishment of timber species. In this paper ...we present the results of an experimental enrichment planting with moabi (
Baillonella toxisperma Pierre), a valuable and important timber species harvested in Central Africa. Although forest gaps are generally considered as favourable for the regeneration of this species, a survey conducted in a forest concession in south-eastern Cameroon provided an estimate of only 12.7
seedlings
ha
−1, suggesting that the species was, in fact, poorly represented in logging gaps within the study area. To further investigate the dynamics of the moabi in logging gaps, 795 seeds were sown in 15 logging gaps and 410 nursery-raised seedlings were planted in 15 other gaps. A biannual monitoring program over a 30-month period showed a lower survival rate for seedlings from sowing (75.9%) compared to that of nursery-raised seedlings (95.3%). Planted seedlings reached an average of 229.3
cm tall whereas seedlings from sowing were 167.5
cm tall, with the observed difference roughly corresponding to the average height of the nursery-raised seedlings at the time they were introduced to the logging gaps. After 30 months, the diameters of planted seedlings (16.8
mm) were also greater than those of the directly sown individuals (12.5
mm). Forest gap characteristics significantly influenced the growth of the plants. Factors accounting for the differences were total solar radiation, the soil content of coarse sand, the topographic position of the gap, the vegetation cover and the density of
Macaranga spp. Whilst total solar radiation had a positive influence on growth, the remaining factors had impacted growth negatively. A streamlined technique was tested by planting 7 seedlings in 250 gaps. Without additional site maintenance, 29.3% of the moabi seedlings emerged naturally from the competing vegetation after 24 months. With biannual maintenance some 89.4% of seedlings became successfully established. Clearance operations had no significant influence on the height of plants whilst plant diameter was greater in cleared gaps. The total cost of the enrichment technique was 5.5
EUR per gap without maintenance and 7.5
EUR per gap with a single maintenance measure. Whilst long-term monitoring is needed, this study suggests a high survival rate of moabi introduced in logging gaps, and a growth rate 10 times higher than previously reported under canopy cover. These findings, combined with the low costs of the enrichment technique, support the use of silvicultural measures in logging gaps to restore the forest.
Both intrinsic and extrinsic factors recorded at individual nests can predict offspring fitness and survival but few studies have examined these effects in the tropics. We recorded nestling survival, ...post‐fledging survival and age at first return of Roseate Terns breeding at Aride Island, Seychelles, over a 12‐year period (1998–2009). Nest data recorded at the egg, nestling and fledging stages were collected during six breeding seasons (1998, 2001–2005) and a capture‐mark‐recapture dataset of six cohorts of fledglings was obtained from 2001–2009. Logistic regression models were used to assess the predictive effect of reproductive variables on fledging success, while multistate capture‐mark‐recapture models were used to estimate post‐fledging survival and return–recruitment probabilities to the natal site. Nestling survival probability increased with earliness of laying and was negatively affected by tick infestation during the growth period (0–23 days). Fledging probability was also positively related to chick body condition, whereas other pre‐fledging reproductive parameters such as clutch size and egg size were not influential. A multistate modelling of age‐specific survival and return–recruitment (transition) rates found that first‐year survival differed between cohorts and was also negatively affected by tick infestation. Annual survival stabilized from age 2 onwards at 0.83 ± 0.02. Transition rates were positively related to body condition at fledging, with heavier individuals returning for the first time to the natal colony at a younger age compared with lighter individuals. These results highlight the importance of local conditions encountered by tropical seabirds during the breeding season in shaping demographic parameters.
We assessed the influence of inter-annual changes in primary productivity and local, regional and large scale ocean indices on the breeding parameters of roseate ternsSterna dougalliion Aride Island, ...Seychelles, western Indian Ocean. Productivity (chicks per breeding pair), timing of breeding and clutch and egg sizes were monitored annually for 8 yr and correlated with local ocean productivity (denoted by Sea-viewing Wide Field-of-view Sensor, SeaWiFS, estimates of chlorophyll concentration, CC), sea surface temperature and indices recording the status of the Indian Ocean Dipole and of El Niño. The rate of increase in CC between mean laying date and CC peak value was positively related to roseate tern productivity and mean clutch size over the 1998 to 2005 study period. Colony productivity seemed also to be influenced by the Multivariate El Niño Index. In most years, the breeding phenology of roseate terns corresponded to the local increase in CC around Aride, and failure to adjust timing of reproduction to the timing of the phytopankton bloom decreased the probability of breeding success. This is the first study showing that a tropical seabird species is sensitive to inter-annual variations in the intensity and timing of the phytoplankton bloom, which should be connected to annual variations in the availability of its main fish prey (juvenile goatfishes). Overall, these patterns indicate that the reproduction of this top marine predator is dictated by the temporal variability in oceanographic conditions. We suggest that CC data available over the world’s oceans may be a useful tool to develop models predicting the fate of colonies of inshore feeding seabirds when other, more conventional, monitoring methods cannot be used.
We investigated inter-annual variability in the breeding performance of six tropical seabirds with different life histories. We further examined the extent to which presumed differences among years ...in food availability to seabirds were related to large-scale oceanic processes (El Niño Southern Oscillation and Indian Ocean Dipole) or local features around the colony (Sea Surface Temperature—SST, chlorophyll-a concentration, wind patterns, association with underwater predators). Two food shortages were recorded: (1) a short-term event operating at a local-scale, lacking any relationship with any measured oceanographic parameters and affecting only a few seabird species; (2) a generalized and protracted event, strikingly characterized by low SST, possibly induced by a La Niña and/or negative IOD event, and with detrimental impacts in the whole seabird community. Overall, species with inflexible feeding habits and fast chick growth rates were more affected by food shortage events than those with more plastic life-history traits.
Inference studies from body mass during the non-breeding season are rare in seabirds due to methodological difficulties to sample individuals. Here, we used 12 years of data collected from 2000 to ...2019 on about 6800 birds mist-netted at La Somone, Senegal along the East Atlantic Flyway to examine the role of intrinsic and environmental factors in explaining body mass variation in both Common
Sterna hirundo
and Roseate
S. dougallii
Terns. Most captured terns were subadults and adults aged three years and older, although ca. 22% of trapped Common Terns were immatures aged one–two years. Mean body mass values of Common and Roseate Terns were substantially lower than published values reported from European breeding sites. In both species, females were, on average, lighter than males, and in the Common Tern, immatures were also lighter than older individuals. Based on the subset of recoveries of birds initially marked at birth in Europe, we found significant differences in body mass according to natal origin in Common Terns but not in Roseate Terns. The variations reported for the former species were mainly attributed to size, with lighter and smaller individuals originating from the British Isles, intermediate individuals from western/central Europe, and heavier and larger birds from Fennoscandian countries. Capture date, used as a proxy measure of timing of migration, showed a strong covariation with body mass in both species. In fact, as the spring season progressed, mist-netted birds became progressively heavier, irrespective of age and natal origin. This suggests that earlier and lighter migrants may have opted for a more protracted migration duration involving more frequent and/or longer refueling periods. Conversely, late migrants needed greater body reserves to achieve the return journey to the colonies within a shorter period to arrive on time for the breeding season. Global climate phenomena such as the North Atlantic and Southern Oscillation indices did not explain inter-annual variations in body mass during the course of this study. Overall, our results suggest that, during the non-breeding season, body mass in these two long-distance migratory species is mainly shaped by intrinsic factors and inter-individual variation in migration strategy.
Most attempts to link seabirds and climate/oceanographic effects have concerned the Atlantic and Pacific Oceans with comparatively few studies in the tropical Indian Ocean. This paper examines the ...reproductive response of the lesser noddy Anous tenuirostris to temporal fluctuations in oceanographic and climatic conditions using 8 years of monitoring data from Aride Island (Seychelles), tropical Western Indian Ocean. We tested the hypothesis that breeding parameters (mean hatching date, mean egg size, hatching and fledging successes) and chick growth are influenced by local, seasonal oceanographic conditions as expressed by ocean primary productivity (surface chlorophyll-a concentrations; CC), sea surface temperature (SST) and wind speed. We also examined the relationship between lesser noddy breeding parameters and climate conditions recorded at the basin-wide scale of the Indian Ocean (Indian Ocean Dipole Mode Index, DMI). Our findings suggest that birds had a tendency to lay slightly larger eggs during breeding seasons (years) with higher CC during April–June (pre-laying, laying and incubation periods). Hatching date was positively related to SST in April–June, with the regression parameters suggesting that each 0.5 °C increase in SST meant a delay of approx.10 days in hatching date. A negative linear relationship was also apparent between hatching success and SST in June–August (hatching and chick-rearing periods), while the quadratic regression models detected a significant effect of wind speed in June–August on fledging success. Body mass increments of growing chicks averaged over 7-day periods were positively related with (2-week) lagged CC values and negatively related with (2-week) lagged SST values. No significant relationship between DMI and lesser noddy breeding parameters was found, but DMI indices were strongly correlated with local SST. Altogether, our results indicate that the reproduction of this top marine predator is dictated by fluctuations in local environmental conditions around the colony, while the effects of large-scale oceanographic processes (DMI) on our study population might be mediated by an effect on local SST.
PDF
