Raptors breeding on weaver nests in trees and on man-made structures

Several raptor species nest on top of large weaver nests. These weaver nests are usually sited in trees, but 11.7% of Red-billed Buffalo-Weaver Bubalornis niger and 25.7% of Sociable Weaver Philetairus socius nests occur on man-made structures. In an extensive literature search, a total of 16 raptor species were recorded as nesting on top of weaver nests. At least 10 raptor species used weaver nests built in trees. Seven raptor species used weaver nests on man-made sites and four raptor species only used weaver nests built on man-made sites. No owls have been recorded as using weaver nests on man-made sites. There are historical records of raptors nesting on top of weaver nests in trees, while nesting on top of weaver nests sited on man-made structures appears to be a more recent adaptation. Costs and benefits of nesting on man-made sites are briefly listed. Nesting on man-made sites may increase (by both weavers and raptors) and raptor researchers are encouraged to document cases of raptors nesting on weaver nests where these are placed in trees or artificial sites, so that there is a record of changes in frequency of nest site usage by raptors.     

Systematic review of a new orb‐weaving spider genus (Araneae: Araneidae), with special reference to the Australasian‐Pacific and South‐East Asian fauna

The Australasian‐Pacific and South‐East Asian species of the new orb‐weaving spider genus Plebs with Plebs eburnus (Keyserling, 1886) as type species are revised. Following this study, Plebs includes a total of 22 species of which seven are here described new. Seven species are found in Australia, two in the Pacific region (New Caledonia, Vanuatu), and two in South‐East Asia (Papua New Guinea, The Philippines). Eleven Asian species are transferred to the new genus. Plebs represent comparatively small orb‐weaving spiders of c. 1.2–15.0 mm body length with a slightly elongated abdomen and humeral (shoulder) humps. Males of most species have two to three stout setae on the ventral side of their fourth coxae. Male pedipalps are characterized by the presence of a single macroseta on the patella, the presence of a paramedian apophysis as basal extension of the conductor, and an apical tegular protrusion. The female epigyne has a scape that is generally much longer than wide. It does not have a terminal pocket and is frequently broken off in a number of species. A phylogenetic analysis of 15 species of Plebs (those for which both sexes are known), 13 Australian/Pacific orb‐weaving spider species representing the most commonly collected clades with paramedian apophysis, three species of Nearctic Eriophora Simon, 1864, and Araneus diadematus Clerck, 1758, as outgroup, identified a single synapomorphy of Plebs based on 35 morphological and three behavioural characters: a distinct, inverted U‐shaped light pattern on the ventral side of the abdomen with two additional white spots anterolateral to the spinnerets. This analysis recovered a monophyletic clade of all Asian Plebs, suggesting a single colonization event of the genus that putatively originated in Australia. Most Plebs species appear to be active during the day. They build a regular orb‐web with vertical stabilimentum in grass and low shrubs. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 279–341.     

Birds adopting weaver nests for breeding in Africa

Weavers build domed, long-lasting nests that may also be adopted by other species for breeding, probably reducing the energetic costs of nest building to varying degrees. In an extensive literature search, 57 species were found to have at least one record of adopting a weaver nest. There is one known obligate nest user, the Pygmy Falcon Polihierax semitorquatus. Four species were classed as near obligate nest adopters. Four species were listed as common, 10 as occasional, and 38 species as rare nest adopters. Other than the falcon and lovebirds Agapornis species, these nest adopters are passerines. Of the 57 species of nest adopters, 35 species had confirmed eggs and/or chicks found in the weaver nests. Most nest adopter species were in the Estrildidae family (20 species), with three estrildids classed as near obligates. This was followed by the Muscicapidae family, species that build cup nests. By building their cup nests inside weaver nests, there is likely protection from adverse weather and predators. Overall, there appeared to be a large diversity of nest adopter species for the traditional savanna living weavers (Ploceus, Bubalornis, Anaplectes, Plocepasser and Philetairus).     

Memory of distances and directions moved as cues during temporary spiral construction in the spiderLeucauge mariana (Araneae: Araneidae)

The spider Leucauge marianaprobably uses the presence of temporary spiral (TSP) lines already in place to determine sites of attachment of currently produced loops of temporary spiral, but less rigidly than has been previously supposed for orb weavers. Memory of distances and directions traveled recently to and from TSP lines is implicated by the fact that adjustments to experimental and natural discontinuities in previous TSP lines occur gradually rather than being abrupt. Distances and directions traveled along both radii and previous TSP lines correlate with relative amounts of adjustment. Body size may also be used as a reference measure, but not in the simple, inflexible way suggested by R. W. G. Hingston (A Naturalist in Himalaya,Small, Maynard, Boston, 1920). Tensions on radii are not used as cues in any simple way, and may not be used at all, since experimental changes in tensions produced effects consistent with resulting changes in thread positions but inconsistent with tension differences.