Perch availability and ground cover: factors that may constitute suitable hunting conditions for pale chanting goshawk families

We investigated the impact of perch height and abundance, and the cover for prey, on the hunting tactics of perch-hunting pale chanting goshawks (Malierax canorus). Mhough pale chanting goshawks demonstrate a clear preference for perching on the highest available perches, the availability of perches is of more importance than height because these birds hunt almost exclusively from perches, move regularly between them, and an increased number of perches increases the area of habitat accessible for effective hunting. In Succulent Karoe, pale chanting goshawks occupied areas where perch density (16 natural and 122 artificial/25 hal was significantly higher than in unoccupied areas (8 natural and 12 artificial/25 hal. The high proportion of cover formed by natural perches (trees and shrubs; 36%) and the low proportion of open ground (42%) resulted in Closed Spekboomveld being unsuitable for pale chanting goshawks, relative to the adjacent Open Spekboomveld that supported goshawks by offering a less restricted view of the ground and prey (perch cover 18% and open ground 49%). In Karroid Broken Veld, the combination of perch availability (3 026/25 hal and open ground (62%) may provide the most suitable conditions for hunting rodent prey near cover or in the open. We suggest that such habitat may also provide a pathway, through fitness benefits gained, in the development of delayed dispersal and cooperative breeding in pale chanting goshawk families.S. Afr.J. Zool. 1997,32(1

Territory and nest defence in polyandrous pale chanting goshawks: do co-breeders Help?

The behaviour of polyandrous and monogamous pale chanting goshawks Melierax canorus was investigated to determine if co-breeders, by defending the territory and nest contents, helped to increase the fitness of polyandrous trios. Polyandrous trios consisted of a female and male breeder, as well as a subordinate co-breeding male. Pale chanting goshawk males performed most of the interspecific territorial maintenance duties, as well as participating in aggressive intraspecific interactions against other mates on territory borders. Intraspecific territorial interactions were almost exclusively recorded in high-quality habitat, Karroid Broken Veld, and probably functioned in the defence of foraging habitat and potential mates, In this habitat, males of polyandrous families largely occupied exclusive sections of a territory. It is suggested that the cost of defending territories in Karroid Broken Veld was offset by the co-breeder’s contribution to high-risk, intraspecific territorial defence. During the nestling period females of polyandrous trios stayed at nesting sites for longer periods than did monogamous females and all males, enabling these females to guard the nest and act as sentinels. Predation of nestlings was recorded at the nests of monogamous pairs, but not at those of polyandrous trios. Co-breeders did not guard the nesting site but contributed directly to nest defence by either coming to the female‘s aid when solicited, or attacking potential predators when present at the nesting site. Co-breeders may also have helped indirectly, through activities such as provisioning prey to females that relieved them of their hunting duties. We suggest that the female’s nest guarding and the resulting lower nest predation may hold reproductive and fitness benefits for polyandrous breeders

Predation on tent tortoise and leopard tortoise hatchlings by the pale chanting goshawk in the Little Karoo

Predation by the pale chanting goshawk Melierax canorus on Psammobates tentorius and Geochelone pardalis hatchlings correlates with the habitat preference of these tortoise species as well as with the breeding pattern of P. tentorius. It is not known why the particularly abundant Chersìna angolata was not preyed upon

Temporal and spatial patterns of abundance and breeding activity of Namaqua sandgrouse in South Africa

We examined various measures of temporal and spatial patterns of abundance and breeding activity of Namaqua sandgrouse Pterocles namaqua (presumably mostly for P. n. furvus) in South Africa. Bird-atlas maps indicating reporting-rates and extensive-counts showed that the majority of Namaqua sandgrouse concentrate in Bushmanland, in the north-western Cape Province, from December to March. From April to July the sandgrouse move north and east of Bushmanland and apparently return to Bushmanland from August to November. This west-east movement occurs at a relatively constant rate of 30-50 km per month. Only 15% of the sandgrouse ringed at an estate within the eastern part of this species range returned the following winter. Follicle diameter and brood-patch measurements increased significantly from July to August, at the time when the majority of birds leave the estate. Belly-soaking was more prevalent in early summer in Bushmanland than in any season in the east. South African populations of Namaqua sandgrouse are partial migrants which breed primarily in early summer (October - November) in Bushmanland

Pengaruh Model Pembelajaran Inkuiri Terhadap Kemampuan Menulis Teks Ulasan Drama Siswa Kelas XI Smk Negeri 8 Medan Tahun Pembelajaran 2015/2016

Penelitian ini bertujuan untuk mengetahui pengaruh model pembelajaran inkuiri terhadap kemampuan menulis teks ulasan drama siswa kelas XI SMK Negeri 8 Medan. Sampel penelitian berjumlah 36 siswa yang ditetapkan dari sebagian jumlah populasi yang ada, sebanyak 464 siswa.Penelitian ini bersifat eksperimen dengan model one group pre-test post-test design. Dari pengolahan data diperoleh hasil pre-test dengan rata-rata 52,22 standar deviasi 12,933 serta empat kategori nilai yakni katgori sangat baik 0%, baik 19,5%, cukup baik 2,5% dan kurang baik 55,5% sedangkan hasil post-test diperoleh rata-rata 87,5 standar deviasi 11,149 dengan empat kategori nilai yakni kategori sangat baik 66,7% kategori baik 27,8% kategori cukup baik 5,5% dan kategori kurang baik 0%. Dari uji homogenitas didapat bahwa sampel penelitian ini berasal dari populasi yang homogen. Setelah uji normalitas dan homogenitas, didapatlah to sebesar 12,228 setelah to diketahui, kemudian dikonsultasikan dengan ttabel pada taraf signifikan 5% dengan df = N-1 = 36-1 = 35, dari df 35 diperoleh taraf signifikan 5% = 2,03. Karena to yang diperoleh lebih besar dari ttabel yaitu 12,228 > 2,03 hipotesis alternatif (Ha) diterima. Berdasarkan analisis data di atas dapat disimpulkan bahwa model pembelajaran inkuiri berpengaruh secara positif terhadap kemampuan menulis teks ulasan drama siswa kelas XI SMK Negeri 8 Medan Tahun Pembelajaran 2015/2016

A Non-dimensional Characterization of Structural Vibration Induced Vertical Slosh Damping

Τhis paper aims to present a non-dimensional analysis which characterises the structural vibration induced slosh damping for a single-degreeof-freedom (SDOF) tank system under vertical motion. We identify several key non-dimensional relations which are then characterised in terms of slosh loads and dissipated power using volume of fluid (VoF) computational fluid dynamics (CFD) simulations. Scaling-laws are then constructed for future quantification of these phenomena. The fitted scaling rules are shown to offer a clear correlation for the selected SDOF system, contingent on minimal changes to the flow Weber number

A momentum-conserving, consistent, Volume-of-Fluid method for incompressible flow on staggered grids

The computation of flows with large density contrasts is notoriously difficult. To alleviate the difficulty we consider a consistent mass and momentum-conserving discretization of the Navier-Stokes equation. Incompressible flow with capillary forces is modelled and the discretization is performed on a staggered grid of Marker and Cell type. The Volume-of-Fluid method is used to track the interface and a Height-Function method is used to compute surface tension. The advection of the volume fraction is performed using either the Lagrangian-Explicit / CIAM (Calcul d'Interface Affine par Morceaux) method or the Weymouth and Yue (WY) Eulerian-Implicit method. The WY method conserves fluid mass to machine accuracy provided incompressiblity is satisfied which leads to a method that is both momentum and mass-conserving. To improve the stability of these methods momentum fluxes are advected in a manner "consistent" with the volume-fraction fluxes, that is a discontinuity of the momentum is advected at the same speed as a discontinuity of the density. To find the density on the staggered cells on which the velocity is centered, an auxiliary reconstruction of the density is performed. The method is tested for a droplet without surface tension in uniform flow, for a droplet suddenly accelerated in a carrying gas at rest at very large density ratio without viscosity or surface tension, for the Kelvin-Helmholtz instability, for a falling raindrop and for an atomizing flow in air-water conditions

A provably stable and high-order accurate finite difference approximation for the incompressible boundary layer equations

In this article we develop a high order accurate method to solve the incompressible boundary layer equations in a provably stable manner. We first derive continuous energy estimates, and then proceed to the discrete setting. We formulate the discrete approximation using high-order finite difference methods on summation-by-parts form and implement the boundary conditions weakly using the simultaneous approximation term method. By applying the discrete energy method and imitating the continuous analysis, the discrete estimate that resembles the continuous counterpart is obtained proving stability. We also show that these newly derived boundary conditions removes the singularities associated with the null-space of the nonlinear discrete spatial operator. Numerical experiments that verifies the high-order accuracy of the scheme and coincides with the theoretical results are presented. The numerical results are compared with the well-known Blasius similarity solution as well as that resulting from the solution of the incompressible Navier Stokes equation