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Sex-, size- or age-dependent variation in migration strategies in birds is generally expected to reflect differences in competitive abilities. Theoretical and empirical studies thereby focus on differences in wintering areas, by which individuals may benefit from avoiding food competition during winter or ensuring an early return and access to prime nesting sites in spring. Here, we use GPS tracking to assess sex- and size-related variation in the spatial behaviour of adult Lesser Black-backed Gulls (Larus fuscus) throughout their annual cycle. We did not find sex- or size-dependent differences in wintering area or the timing of spring migration. Instead, sexual differences occurred prior to, and during, autumn migration, when females strongly focussed on agricultural areas. Females exhibited a more protracted autumn migration strategy, hence spent more time on stopover sites and arrived 15 days later at their wintering areas, than males. This shift in habitat use and protracted autumn migration coincided with the timing of moult, which overlaps with chick rearing and migration. Our results suggest that this overlap between energy-demanding activities may lead females to perform a more prolonged autumn migration, which results in spatiotemporal differences in foraging habitat use between the sexes.

GSI Scientific Report 2014 - GSI Report 2015-1

GSI Scientific Report 2014 - GSI Report 2015-1

The recent trend for journals to require open access to primary data included in publications has been embraced by many biologists, but has caused apprehension amongst researchers engaged in long-term ecological and evolutionary studies. A worldwide survey of 73 principal investigators (Pls) with long-term studies revealed positive attitudes towards sharing data with the agreement or involvement of the PI, and 93% of PIs have historically shared data. Only 8% were in favor of uncontrolled, open access to primary data while 63% expressed serious concern. We present here their viewpoint on an issue that can have non-trivial scientific consequences. We discuss potential costs of public data archiving and provide possible solutions to meet the needs of journals and researchers.

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That repeated copulation with the same partner within a single fertile period is beneficial to the male is generally accepted, but why it should be adaptive to die female it controversial and clear evidence supporting any hypothesis is lacking. Hunter et al. (1993) presented seven hypotheses explaining repeated mating from the female perspective. Four of them are consistent with the occurrence of male refusal to copulate: females might trade copulations for (1) immediate and/or (2) future material benefits, or use mating as a mechanism for (3) mate-guarding and/or (4) mate-assessment To test these hypotheses in a population of crested tits Parus cristatus, we collected data on variation in female solicitation rate, proportion of male refusal, and extra-pair paternity. We found that (1) female solicitation rate was independent of male condition, (2) die proportion of male refusal was higher in poor-condition males and (3) females paired to poor-condition males sought extra pair paternity. These findings agree with predictions stemming from the mate assessment hypothesis. Therefore, it is suggested that, in crested tits, male response to female copulation solicitation reflects male condition and is' used by females to assess male quality.

We studied the effect of increased cage size on different aspects of bone quality (bone strength, diameter, weight, and length) and fluctuating asymmetry (FA). Such characteristics may indicate improved animal welfare, as greater bone quality may decrease fracture incidence during handling, whereas decreased FA has been suggested to signal decreased stress. As stress is likely not only influenced by the quantity of space, but also by its quality, we also studied the effect of environmental enrichment. Groups of 8 rabbits were housed in wire open-top cages of 0.40, 0.46, 0.53, 0.64, 0.80, 1.07, and 1.60 m(2) from weaning until slaughter. All cages of 0.40 and 0.46 m(2) (12 cages/size) were left barren to allow sufficient mobility. One-half of the larger cages were enriched with a wooden-enrichment structure that could be used to gnaw on, hide in, or lie in (6 cages per size x enrichment treatment). Increased cage size led to an increase in tibiofibula diameter (P = 0.008), a tendency for increased tibiofibula weight (P = 0.051), and decreased FA (P = 0.010), suggesting improved welfare. Bone length and strength were not affected by cage size (P > 0.1). Enrichment did not affect FA (P > 0.1), in contrast with our expectations based on previous glucocorticoid analysis. This discrepancy between indicators may be due to sensitivity to other types of stressors or different sensitive periods. In summary, rabbits housed in larger cages had wider, heavier bones, but the absence of changes in bone strength indicate that this is unlikely to result in decreased fracture incidence. In larger cages, FA was lower, suggesting a favorable effect on welfare, whereas no effect of enrichment was shown.

Studies of migration have revealed multiple trade-offs with other life-history traits that may underlie observed variation in migratory properties among ages and sexes. To assess whether, and to what extent, body size and/or sex-specific differences in competition for resources (e.g. breeding territories or winter food) may shape variation in migration distance and timing of arrival in ecologically and phylogenetically related species, we combined over 30 000 sightings of individually marked, sexually mature males and females of Herring Gulls Larus argentatus and Lesser Black-Backed Gulls Larus fuscus with biometric measurements and phenological observations at a mixed breeding colony. In L. argentatus, larger males migrated further from the breeding colony, whereas migration distance was independent of body size in adult females. In L. fuscus, no relationship between body size and migration distance was apparent in either sex. Mean arrival dates at the breeding colony did not vary with migration distances but differed between males and females of L. argentatus (but not L. fuscus). As allometry at least partly explains sexual segregation in migration behaviour in L. argentatus, but not in L. fuscus, we conclude that the effect of body size on sex-related migratory strategies may vary between closely related, sympatric species despite similar size dimorphism.

De invloed van antropogene druk en veranderende leefomstandigheden op genetische variatie en genetische uitwisseling tussen populaties van Huismussen, en de kansen voor instandhouding van deze soort

The structure and composition of the indigenous forest fragments of the Taita Hills of south-east Kenya were analysed. We collected data in all of the large forest fragments using Point Centred Quarter extensive surveys, supplementing these data with intensive surveys of 20 x 20 m plots. Our structural data on basal area per unit area, stem density, canopy cover, shrub density, stratification and extent of herbaceous ground cover clearly show that the largest fragment, Mbololo, is also the least disturbed. The next largest fragment, Ngangao, has suffered from intermediate levels of disturbance, and all other fragments have been very heavily impacted. Tree size class distributions show that nearly all of the large circumference trees have been lost from the smallest fragments, while the Chawia forest is selectively losing its small, easily-cut trees. Finally, we mapped the Importance Values (combined standard measures of abundance, biomass and dispersion) of each forest's tree species. The map indicates the forest biogeography of the region but also shows the extent to which all of the fragments except Mbololo and Ngangao are dominated by a very few secondary successional sub-canopy species. Only Mbololo and Ngangao may be viable forests in the long term.Journal of East African Natural History Vol. 87 (1&2) 1998: pp. 181-187

1. In fragmented landscapes where natural disturbance acts at the local level, community composition can be altered either by 'species-by-species matching', with community-wide character displacement, or by 'constrained species sorting', whereby disturbance favours species with distinct ecological traits. It is necessary to understand such species shifts when aiming to detect bottlenecks associated with changing disturbance dynamics at different spatial levels. Such an understanding also provides insight into the underlying ecological mechanisms in operation and allows identification of species of conservation concern.2. This approach to understanding species' shifts was applied to a study of spider diversity and life-history variation in relation to sand dynamics in stabilized and dynamic grey dune landscapes located along the coasts of France, Belgium and the Netherlands.3. Local (alpha) diversity appeared to decrease with increasing local sand dynamics in both stable and dynamic landscapes. In dynamic dune landscapes, beta-diversity decreased significantly and approached regional (gamma) diversity under local grey dune stabilization; in stabilized landscapes, beta-diversity was not affected by local sand dynamics.4. Comparative analyses of ecological traits revealed shifts in life-history patterns, suggesting that patterns in local diversity resulted from species sorting. Species from fragments characterized by high sand dynamics showed narrower niche breadths, larger body sizes and longer generation times, while summer-active species tended to become residential after sand stabilization. This provides evidence for constrained species sorting in which natural disturbance (through local sand dynamics) allows only species with distinct ecological traits to persist.5. Synthesis and applications. Species with larger body sizes, longer generation times and a higher degree of habitat specialization (i.e. related to dispersal ability) would be expected to be more vulnerable at dynamic sites and more prone to extinction than their counterparts from stabilized fragments. In particular, species with a burrowing lifestyle would be expected to go extinct locally as a result of increasing soil development and soil hardness. Shifts in species composition were found to be more pronounced in dynamic landscapes. Hence ensuring conservation of sand dynamics at a landscape level rather than at a local level is of prime importance when aiming to conserve typical psammophilous spider species within local assemblages in grey dune habitats.

We describe a field experiment for examining the impact of wild rabbits (Oryctolagus cuniculus L.) on the vegetation in two Flemish coastal dune grasslands. When numerous, rabbits had a major impact on the vegetation. This impact can be considered positive in the case of the studied grasslands, as evidenced by a decreasing abundance by dominant grass species and a declining species richness. The decrease of the number of rabbits, due to VHS, may hence negatively affect dune grassland species richness. Introducing large herbivores can be part of the solution for preserving the dune grasslands, and this introduction may even have positive effects on rabbit populations through feeding facilitation.