Cooperative breeding and delayed dispersal in the Pale chanting goshawk, Melierax canorus

Bibliography: pages 251-265.A population of Pale Chanting Goshawks Melierax canorus, some of which live in families, was studied during 1988-1992 for a total of 117 group-years near Calitzdorp, South Africa. The aims of the study were to identify ecological and social factors that might predispose individuals in the population to delay dispersal and become non-breeding or co-breeding members of Pale Chanting Goshawk families, and to determine why cobreeders breed cooperatively in polyandrous trios. In all vegetation types within the study area, non-breeders, as juvenile and adult offspring, delayed dispersal from their natal territories. However, co-breeding males occurred only in one vegetation type, Karroid Broken Veld. Co-breeding males participated in all reproductive activities, including copulation. Karroid Broken Veld also supported the largest known groups of Pale Chanting Goshawks and the highest frequency of groups with non-breeders, which resulted in some of the highest recorded single species raptor densities in the Afrotropics. Pale Chanting Goshawks in Karroid Broken Veld preyed primarily on two otomyinid rodents, Otomys unisulcatus (42-48 % of prey biomass) and Parotomys brantsii (18-32 % ). The habitat quality of Karroid Broken Veld for Pale Chanting Goshawks was high since, compared with other vegetation types, it incorporated: (1) optimal habitat for otomyinid prey, (2) a very high estimated biomass of otomyinids, almost twice that of other vegetation types, and (3) a hunting habitat with an optimum combination of prey visibility and perch availability that facilitated hunting efficiency. Territorial space was limited throughout the study area, constraining the number of nonbreeders per group to two and inhibiting new breeders from establishing territories. Juvenile non-breeders probably delayed dispersal to increase their probability of survival, and dispersed later as sexually mature adults, since they could not increase their fitness further by becoming helpers at the nest. During the nestling period, co-breeding beta males provided prey at an equal rate to dominant males, that enabled polyandrous trios to undertake more frequent and successful breeding attempts in years of high prey abundance. The help provided by co-breeders contributed more to this success than did density of dominant prey and territory size. In Karroid Broken Veld co-breeders delayed dispersal since their fitness as subordinate sibling males was probably higher than fitness achieved due from dispersing to a breeding vacancy in habitat of lower quality. I suggest that those ecological factors which contribute to habitat quality provided the proximate impetus, and the resulting saturation of the habitat the ultimate impetus, in promoting the establishment of Pale Chanting Goshawk family units. Once Pale Chanting Goshawk formed families, a range of secondary benefits evolved as birds adjusted their behaviour to benefit from the presence of other group members. For example, although breeders in high-quality habitat produced the highest number of offspring, the lack of territorial space probably forced more offspring to disperse. To increase offspring survival, breeders may have adjusted their reproductive strategy and allow non-breeders to partake and share in returns of cooperative hunts. Other secondary benefits included the possibility of inheriting a natal territory, budding-off onto territorial borders or helping close relatives as an experienced co-breeder

A policy approach towards achieving regional economic re-silience in developing countries : evidence from the SADC

Abstract: External economic shocks such as the global financial crisis (GFC) affect regional economic growth in developing regions through impacting export demand and capital inflows. Resilience to these economic shocks—i.e. the ability to recover from the initial impact and prolonged effects of said shocks—is influenced by the inherent vulnerability of regional economies to their impact. The research objective is to investigate regional economic resilience policy in the context of the Southern African Development Community (SADC), and the wider perspective of trading blocs among de-veloping countries. Central hereto is undertaking an equilibrium and econometric analysis to iden-tify endogenous and exogenous factors of the regional economy that influence economic resilience. Analysis findings indicate that economic openness, export market dynamics and sectoral composi-tion may influence economic resilience. SADC vulnerability may be attributed to the dependence on foreign direct investment (FDI) inflows and exports to higher-income markets, relatively low import tariffs and the comparative importance of tertiary activities to output. A balanced regional policy approach is required: one focused on industrialization, while incorporating elements to sup-port economic resilience. The latter includes increased intra-regional trade anchored in the devel-opment of regional supply and value chains which support primary sector activities, and capaci-tated supranational institutions to oversee regional integration initiatives

Natural compulsive-like behaviour in the deer mouse (Peromyscus maniculatus bairdii) is associated with altered gut microbiota composition

Obsessive–compulsive disorder (OCD) is a psychiatric illness that significantly impacts affected patients and available treatments yield suboptimal therapeutic response. Recently, the role of the gut–brain axis (GBA) in psychiatric illness has emerged as a potential target for therapeutic exploration. However, studies concerning the role of the GBA in OCD are limited. To investigate whether a naturally occurring obsessive–compulsive‐like phenotype in a rodent model, that is large nest building in deer mice, is associated with perturbations in the gut microbiome, we investigated and characterised the gut microbiota in specific‐pathogen‐free bred and housed large (LNB) and normal (NNB) nest‐building deer mice of both sexes (n = 11 per group, including three males and eight females). Following baseline characterisation of nest‐building behaviour, a single faecal sample was collected from each animal and the gut microbiota analysed. Our results reveal the overall microbial composition of LNB animals to be distinctly different compared to controls (PERMANOVA p < .05). While no genera were found to be significantly differentially abundant after correcting for multiple comparisons, the normal phenotype showed a higher loading of Prevotella and Anaeroplasma, while the OC phenotype demonstrated a higher loading of Desulfovermiculus, Aestuariispira, Peptococcus and Holdemanella (cut‐off threshold for loading at 0.2 in either the first or second component of the PCA). These findings not only provide proof‐of‐concept for continued investigation of the GBA in OCD, but also highlight a potential underlying aetiological association between alterations in the gut microbiota and the natural development of obsessive–compulsive‐like behaviours

The relative influence of prey abundance and co-breeders on the reproductive performance of polyandrous Pale Chanting-goshawks

This study investigates if the reproductive performance of polyandrous Pale Chanting-goshawks, Melierax canorus, is governed by the abundance of dominant rodent-prey species or a co-breeding male participating fully in prey being delivered to the female and young. Polyandrous trios in prey-rich habitat, the only habitat where these trios occurred, failed to produce more offspring than monogamous pairs, but attempted more second broods in years of high prey abundance. The higher the prey-delivering rates at the nesting sites by either one monogamous male or two polyandrous males (combined effort), the higher the proportion of time their females spent in close proximity to the nest. Since there were no significant differences between the body masses of nestlings fledged by polyandrous and monogamous groups, higher delivery rates relieved females from away-from-the-nest hunting duties and permitted them to feed on prey not fed to offspring. Although breeding in polyandrous trios held fitness benefits for females, e.g. to accumulate the necessary body reserves for laying a second clutch in years of high prey abundance, it is still not clear how males benefited. The reproductive performance of each group was strongly linked to the abundance of the dominant, otomyine rodent prey (Otomys unisulcatus and Parotomys brantsii) and it was therefore prey abundance, and not the number of males delivering prey to the female and nestlings at each nesting site, that controlled the reproductive performance of cooperative-breeding Pale Chanting-goshawks.Ostrich 2004, 75(1&2): 44–5

Reproductive partitioning among polyandrous alpha and beta pale chanting-goshawk males

This study investigates the reproductive and parental roles of polyandrous male pale chanting-goshawks, Melierax canorus, and speculatively reviews the fitness outcomes of different skew and relatedness scenarios. The study was conducted over five years in the Little Karoo, South Africa. Although, polyandrous males participated equally in building nests, provisioning prey and incubating, in the fertility window the dominant alpha males copulated 31–5 days before the females laid, whereas subordinate beta males only copulated 5–3 days before laying. If this copulation timing by alpha males was indicative of a high reproductive skew, alpha males breeding as full sibs could skew paternity in their favour (ratio 68:32) and produce 0.69 offspring equivalents. Under this scenario, they compensated beta males with indirect fitness benefits by allowing them to produce 0.54 offspring equivalents, equal to monogamous males. Alternatively, if beta males controlled reproduction while breeding with non-relatives under a high skew scenario, they would have to restrain themselves to avoid eviction and produce 0.28 offspring equivalents to allow the fitness of alpha males at least to equal that of monogamous males. I suggest that alpha males and their females altered their reproductive roles to accommodate beta males, thereby increasing their inclusive fitness, whereas beta males tolerated subordination to acquire reproductive skills that non-breeder males do not have access to.Keywords: pale chanting-goshawk, dominance, cooperative breeding, inclusive fitness, reproductive ske

Nest site selection of the Southern Pale Chanting Goshawk in the Little Karoo, South Africa

This study investigated whether Southern Pale Chanting Goshawks Melierax canorus that est in the low woody vegetation of the arid Little Karoo reduce nest predation by selecting nest trees and sites that are less accessible to and conspicuous for terrestrial predators. The 114 nest trees and shrubs sampled were taller (0 = 4.4m) than surrounding random trees (0 = 3.0m). The birds selected bush clumps for nesting that contained, on average, two plants, including creepers, compared to the 1.4 plants in random clumps. The birds also nested mainly in irregular and dome-shaped trees, a selection that differed from the dominant shapes of random trees. Most nests were placed in the centre of the trees and thorns and shoots covered the main stem of 68% of nest trees. In spite of these preferences, only nest height and — to a lesser extent — nest placement and tree shape, prevented predation by visually hiding the nest. The other features had no impact on predation, indicating that once a nest was discovered, the predators were able to climb through the foliage to the nest. Pale Chanting Goshawks therefore had some success in hiding their large nests in the low and sparsely-growing arid trees and shrubs. Although 19% of nests studied were depredated, the seasonal, irregular and low-density breeding pattern of the birds probably resulted in their offspring being an unpredictable food source for opportunistic predators.Ostrich 2006, 77(3&4): 119–12