Herder Perceptions on Impacts of Range Enclosures,Crop Farming,Fire Ban and Bush Encroachment on the Rangelands of Borana,Southern Ethiopia

This study focuses on community-based knowledge to analyze the impacts of range enclosures, crop farming, fire suppression and bush encroachment on the communal rangelands of Borana, southern Ethiopia. The knowledge of local herders is the basis for decision making in the utilization and management of grazing lands. We used Borana oral history associated with the period of the gada system to reconstruct environmental change that spans a period of 48 years. Our results show that the use of communities’ perceptions as a basis for evaluating the impacts of land use change on the environment makes an important methodological contribution. Communities’ responses to changing land use resulted in the development of range enclosures, the expansion of crop farming and the fragmentation of the communal rangelands, while the suppression of fire contributed to the expansion of bush encroachment. The overall impact was forage scarcity and greater vulnerability of stock during drought years. We conclude that policymakers could use communities’ knowledge of environmental change to improve the use of the rangelands. We propose that sustainable use of the southern rangelands in the future will require a greater focus on regulating the expansion of enclosures, crop farming and ranching, as well as reintroducing fire where necessary, to control the expansion of bush cover.

Distribution, Habitat and Red List Status of the New Caledonian Endemic Tree Canacomyrica monticola (Myricaceae)

The monotypic genus Canacomyrica Guillaumin is a small tree endemic to the rare remaining fragments of primary forest growing on ultramafic geology in New Caledonia. In the rich flora of this island it is one of many endemics to be threatened by habitat loss due to a variety of factors, most significantly open-cast mining for nickel. Using field observations and data from herbarium specimens the extent of occurrence of Canacomyrica monticola is established to be approximately 1420 km². Within this area the distribution of C. monticola is very fragmented and limited to just 11 known localities. Six localities are outside protected areas; two of these may be imminently threatened by mining activity and another may be threatened by bush fires. It is recommended that the IUCN Red List status of Endangered (EN B1ab (i,ii,iv,v)) is assigned to this species.     

Isolation and characterization of 12 microsatellite loci from Golden‐winged Warblers (Vermivora chrysoptera) with broad cross‐taxon utility in emberizine songbirds

We describe 12 microsatellite loci from the Golden‐winged Warbler (Vermivora chrysoptera), a bird species of conservation concern owing to competition and hybridization with the Blue‐winged Warbler (V. pinus). Directional mitochondral DNA introgression from V. pinus into V. chrysoptera has been reported within the hybrid zone. Frequent hybrid phenotypes suggest that nuclear introgression is also prevalent, although this has not been demonstrated conclusively with molecular markers. These microsatellites will foster explorations of the genetic interactions between these avian congeners, and amplification tests suggest that they have high cross‐species utility for closely allied bird genera and families.     

Seed dispersal by cattle may cause shrub encroachment of Grewia flava on southern Kalahari rangelands

Abstract. Shrub encroachment, i.e. the increase in woody plant cover, is a major concern for livestock farming in southern Kalahari savannas. We developed a grid‐based computer model simulating the population dynamics of Grewia flava, a common, fleshy‐fruited encroaching shrub. In the absence of large herbivores, seeds of Grewia are largely deposited in the sub‐canopy of Acacia erioloba. Cattle negate this dispersal limitation by browsing on the foliage of Grewia and dispersing seeds into the grassland matrix. In this study we first show that model predictions of Grewia cover dynamics are realistic by comparing model output with shrub cover estimates obtained from a time series of aerial photographs. Subsequently, we apply a realistic range of intensity of cattle‐induced seed dispersal combined with potential precipitation and fire scenarios. Based on the simulation results we suggest that cattle may facilitate shrub encroachment of Grewia. The results show that the severity of shrub encroachment is governed by the intensity of seed dispersal. For a high seed dispersal intensity without fire (equivalent to a high stocking rate) the model predicts 56% shrub cover and 85% cell cover after 100 yr. With fire both recruitment and shrub cover are reduced, which may, under moderate intensities, prevent shrub encroachment. Climate change scenarios with two‐fold higher frequencies of drought and wet years intensified shrub encroachment rates, although long‐term mean of precipitation remained constant. As a management recommendation we suggest that shrub encroachment on rangelands may be counteracted by frequent fires and controlling cattle movements to areas with a high proportion of fruiting Grewia shrubs.     

Basal metabolic rate, food intake, and body mass in cold- and warm-acclimated Garden Warblers

We address the question of whether physiological flexibility in relation to climate is a general feature of the metabolic properties of birds. We tested this hypothesis in hand-raised Garden Warblers (Sylvia borin), long-distance migrants, which normally do not experience great temperature differences between summer and winter. We maintained two groups of birds under cold and warm conditions for 5 months, during which their body mass and food intake were monitored. When relatedness (siblings vs. non-siblings) of the experimental birds was taken into account, body mass in cold-acclimated birds was higher than in warm-acclimated birds. BMR, measured at the end of the 5-month temperature treatment, was also higher in the cold- than the warm-acclimated group. Migrant birds thus seem to be capable of the same metabolic cold-acclimation response as has been reported in resident birds. The data support the hypothesis that physiological flexibility is a basic trait of the metabolic properties of birds.     

Seasonal surveillance confirms the range expansion of Aedes japonicus japonicus (Theobald) (Diptera: Culicidae) to the Hawaiian Islands of Oahu and Kauai

The Asian bush mosquito, Aedes japonicus japonicus (Theobald) was not known to occur in the Hawaii archipelago until it was identified on the island of Hawaii in 2003. This mosquito species remained undetected on the neighboring islands for 8?years before it was discovered at the Honolulu International Airport on Oahu in 2012. By 2015, four Ae. j. japonicus mosquitoes were collected in the western mountains of Oahu and one was collected in the central mountains of Kauai. The collection of this invasive mosquito species across the neighboring Hawaiian Islands of Oahu and Kauai indicated the need for increased seasonal surveillance on these islands. Following nearly four years of surveillance, Ae. j. japonicus was also confirmed to occur in the eastern mountains of Oahu and in the central mountainous region of Kauai. To expand the knowledge of the spread of invasive mosquitoes species further surveillance is necessary to identify all possible areas where populations of Ae. j. japonicus and other invasive mosquito species occur in Hawaiian archipelago.     

The effects of force‐fledging and premature fledging on the survival of nestling songbirds

Despite the broad consensus that force‐fledging of nestling songbirds lowers their probability of survival and therefore should be generally avoided by researchers, that presumption has not been tested. We used radiotelemetry to monitor the survival of fledglings of Ovenbirds Seiurus aurocapilla and Golden‐winged Warblers Vermivora chrysoptera that we unintentionally force‐fledged (i.e. nestlings left the nest in response to our research activities at typical fledging age), that fledged prematurely (i.e. nestlings left the nest earlier than typical fledging age), and that fledged independently of our activities. Force‐fledged Ovenbirds experienced significantly higher survival than those that fledged independent of our activities, and prematurely fledged Ovenbirds had a similarly high survival to those that force‐fledged at typical fledging age. We observed a similar, though not statistically significant, pattern in Golden‐winged Warbler fledgling survival. Our results suggest that investigator‐induced force‐fledging of nestlings, even when deemed premature, does not necessarily result in reduced fledgling survival in these species. Instead, our results suggest that a propensity or ability to fledge in response to disturbance may be a predictor of a higher probability of fledgling survival.     

4.—A FIELD-NATURALISTS PEREGRINATIONS

Geldenhuys, J. N. 1983. Morphological variation in wing-moulting South African Shelducks. Ostrich 54:19-25. Male and female South African Shelducks Tadorna cana lose 25,6 and 28,2% of their pre-moult weight during the flightless period. Juveniles (3–5 months old) do not take part in the wing-moult aggregation. Subadults (15–17 months old) cannot be distinguished from older birds in wing-moulting populations on the basis of the bursa of Fabricius, penis structure, colour of the wing feathers, foot colour and the size of the culmen and tarsus. It is suggested that the catabolism of body tissue during wing-moult has little effect on the survival of the species.     

The response of the Great Reed Warbler Acrocephalus arundinaceus to climate change

We examined long-term responses in the breeding performance of the Great Reed Warblers Acrocephalus arundinaceus to climate change. The study took place in various years from 1970 to 2007. During the study period, mean temperatures in the breeding season of the species increased and precipitation decreased significantly. We found evidence for the significant advancement in both earliest and annual median first-egg-laying dates. This advancement correlated with temperature increases early in the season. The latest first-egg laying dates, however, remained unchanged. Other breeding statistics: clutch size, nest losses, and production of young per nest, did not change significantly over the study period. Precipitation did not affect any of the analysed measures. It is important to note, though, that during dry seasons, the production of young per successful nest was higher. In contrast to some woodland species, the Great Reed Warbler seems to adapt well to climate change by shifting laying dates. The reason for this is probably to optimise food resources.