Extrapair paternity in two populations of the socially monogamous Thorn-tailed Rayadito Aphrastura spinicauda (Passeriformes: Furnariidae)

Studies on extrapair paternity (EPP) are key to understanding the ecological and evolutionary drivers of variation in avian mating strategies, but information is currently lacking for most tropical and subtropical taxa. We describe the occurrence of EPP in two populations of a South American socially monogamous bird, the Thorn-tailed Rayadito, based on data from 266 broods and 895 offspring that were sampled during six breeding seasons in north-central and southern Chile. In the northern population, 21% of the broods contained at least one extrapair young and 14% of all offspring were sired by an extrapair male, while in the southern population, we detected extrapair offspring (EPO) in 14% of the broods, and 6% of all offspring were EPO. Variation in the frequency of EPP could stem from population differences in the duration of the breeding season or the density of breeding individuals. Other factors such as differences in breeding synchrony and variation in food availability need to be evaluated. More reports on EPP rates are necessary to determine the patterns of taxonomic and geographic variation in mating strategies in Neotropical birds, and to better understand the differences in ecological dynamics between northern and southern hemisphere populations.Fil: Botero Delgadillo, Esteban. Max Plank Institute For Ornithology; Alemania. SELVA: Investigación para la Conservación en el Neotrópico; Colombia. Universidad de Chile; ChileFil: Quirici, Verónica. Universidad Andrés Bello; ChileFil: Poblete, Yanina. Universidad de Las Américas; ChileFil: Ippi, Silvina Graciela. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Departamento de Ecología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Kempenaers, Bart. Max Plank Institute For Ornithology; AlemaniaFil: Vásquez, Rodrigo A.. Universidad de Chile; Chil

Contrast in Edge Vegetation Structure Modifies the Predation Risk of Natural Ground Nests in an Agricultural Landscape

Nest predation risk generally increases nearer forest-field edges in agricultural landscapes. However, few studies test whether differences in edge contrast (i.e. hard versus soft edges based on vegetation structure and height) affect edge-related predation patterns and if such patterns are related to changes in nest conspicuousness between incubation and nestling feeding. Using data on 923 nesting attempts we analyse factors influencing nest predation risk at different edge types in an agricultural landscape of a ground-cavity breeding bird species, the Northern Wheatear (Oenanthe oenanthe). As for many other bird species, nest predation is a major determinant of reproductive success in this migratory passerine. Nest predation risk was higher closer to woodland and crop field edges, but only when these were hard edges in terms of ground vegetation structure (clear contrast between tall vs short ground vegetation). No such edge effect was observed at soft edges where adjacent habitats had tall ground vegetation (crop, ungrazed grassland). This edge effect on nest predation risk was evident during the incubation stage but not the nestling feeding stage. Since wheatear nests are depredated by ground-living animals our results demonstrate: (i) that edge effects depend on edge contrast, (ii) that edge-related nest predation patterns vary across the breeding period probably resulting from changes in parental activity at the nest between the incubation and nestling feeding stage. Edge effects should be put in the context of the nest predator community as illustrated by the elevated nest predation risk at hard but not soft habitat edges when an edge is defined in terms of ground vegetation. These results thus can potentially explain previously observed variations in edge-related nest predation risk

A comparative perspective on the evolution of tamarin and marmoset social systems

Tamarins and marmosets (callitrichids) present an unusual opportunity for study of the determinants of primate social systems, because both the mating and infant care patterns of callitrichids are variable, even within individual populations. In this paper, I briefly describe three characteristics of callitrichid social systems that distinguish them from most other primates: extensive male parental care, helping by nonreproductive individuals, and variable mating patterns. I then discuss the evolution of these characteristics and of the frequent twinning exhibited by callitrichids. I suggest that an ancestor of modern callitrichids gave birth to a single offspring at a time, mated monogamously, and had significant paternal care. The idea that males of this ancestral form must have provided paternal care, even though only single infants were born, derives from a comparison of litter/mother weight ratios in modern primate species. Twinning perhaps then evolved because of a combination of dwarfing in the callitrichid lineage, leading to higher litter/mother weight ratios, and a high infant mortality rate, and because the extensive paternal care already present facilitated the raising of twins. I propose that the helping behavior of older offspring may have coevolved with twinning, because helpers would have increased the chances of survival of twins, and the presence of twins would have increased the benefits of helping. Finally, the high costs of raising twins and the variability of group compositions, especially the fact that some groups would not have had older offspring to serve as helpers, may have selected for facultative polyandry in saddle-back tamarins ( Saguinus fuscicollis ) and perhaps in other callitrichid species. Both helping and cooperative polyandry have been extensively studied in bird species, and I apply some of the conclusions of these studies to the discussion of the evolution of callitrichid social systems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44556/1/10764_2005_Article_BF02193696.pd

Calliandra grandifolia P.H. Allen

Costa Rica, Puntarenas, Golfo Dulce. Between Golfo Dulce and Río Térraba. LAT (8.4648)N; LONG(83.2436)W. ALT 30. Tree 6 m. Fls. bright red. In forest