FIELD STUDIES OF THE AFRICAN CRAKE CREX EGREGIA IN ZAMBIA AND KENYA

Taylor, P. B. 1985. Field studies of the African Crake Crex egregia in Zambia and Kenya. Ostrich 56: 170–185.

Field observations were made of a breeding population of African Crake Crex egregia at Ndola, Zambia from 1975 to 1980 and of a nonbreeding population at Mombasa, Kenya in 1981. Both populations are migratory and the Kenyan birds are thought to breed in southern Africa. Habitat requirements, migrations and patterns of occurrence are described. Population estimates give the density of breeding birds as 1 bird/2,6ha and of nonbreeding birds as 1 bird/1,99-2,73 ha. Local movements are evident at Mombasa. The crakes are thought to be territorial in both the breeding and nonbreeding seasons and the pair bond is sustained or formed during the nonbreeding season. Habits and behaviour are described, including courtship, copulation, aggression, feeding, roosting and vocalizations. Breeding, moult and predation are briefly discussed.     

Habitat complexity and the structure of vocalizations: a test of the acoustic adaptation hypothesis in three rail species (Rallidae)

The acoustic adaptation hypothesis is based on the assumption that senders are directionally selected to maximize transmission and minimize degradation; however, the two aims are not necessarily convergent. In complex habitats, where more effects that might potentially cause attenuation and degradation co‐occur and longer transmission must incur a higher cost, signals should attenuate faster and have shorter transmission ranges. At the same time, such signals should be more resistant to degradation in order to preserve their communicatory function. Based on a sound transmission experiment, we tested the evidence for these predictions using territorial calls of three sympatric species of rails, inhabiting habitats with increasing complexity: Corncrake Crex crex, Spotted Crake Porzana porzana and Water Rail Rallus aquaticus. In the experiment, the calls were broadcasted with similar amplitudes through a heterogeneous habitat inhabited by all three species and rerecorded at different distances up to 320 m. Despite standardized amplitudes and habitats, calls of the species living in simpler habitats had longer transmission ranges but were more susceptible to degradation than calls of the species living in more complex habitats. Our results suggest that narrow frequency bandwidth is an adaptation of species inhabiting complex habitats that helps their calls to degrade less at the cost of stronger attenuation and shorter transmission range. By contrast, wide frequency bandwidth extends the range but increases degradation and thus it is used only by species inhabiting structurally simpler habitats. This study shows that, in more complex habitats, the clarity of the message is preserved at the cost of range.     

Shelter use and behaviour of juvenile Spotted Wolffish (<Emphasis Type="Italic">Anarhichas minor</Emphasis>) in an experimental context

Laboratory experiments were conducted to assess shelter use and behaviour of juvenile Spotted Wolffish, Anarhichas minor, using time-lapse video. Information about the behaviour of Spotted Wolffish and its habitat utilization is sparse due to the great depth at which this species lives. Four experiments were conducted using one or two fish per tank, with and without a shelter. The positions and movements of fish in the tanks and interactions between fish were monitored over 24-h periods. In experiments in which no shelter was available, Spotted Wolffish spent very little time exploring the water column. They did not show fidelity to a particular area on the bottom of the tank and exhibited few signs of aggressiveness to each other. When a shelter was made available, fish spent most of their time in the shelter or close to the shelter. The presence of a single shelter did not enhance aggressive behaviours in fish kept in pairs. When day and night observations were compared, no clear diel pattern emerged. The Canadian recovery plan for Spotted Wolffish calls for research aimed at describing their use of demersal habitats. The present study suggests that shelter availability might be an important feature of the habitat requirements of juvenile Spotted Wolffish.     

OBSERVATIONS ON THE SLATY EGRET EGRETTA VINACEIGULA IN NORTHERN NAMIBIA

Hines, C.J.H. 1992. Observations on the Slaty Egret Egretta vinaceigula in northern Namibia. Ostrich 63: 118–122.

The Slaty Egret is an endemic African resident with a limited distribution in Botswana, Zambia and Namibia. Distribution records for Namibia are reviewed and information on movements and habitat preferences is given. Diet and feeding habits are described. Two colonies of Slaty Egrets containing eggs and chicks were found on temporary wetlands in eastern Bushmanland. Nests and eggs are described and egg measurements and weights given. The plumage of immature birds is described as well as the variation in adult plumages. The conservation status of the species is reviewed, and the possible importance of temporary wetlands to the Slaty Egret is discussed.     

THE WINTER FEEDING ECOLOGY OF WIGEON AT BRIDGWATER BAY, SOMERSET

The feeding ecology of Wigeon wintering in the vicinity of Bridgwater Bay National Nature Reserve is described. The birds roost on mudflats in the Bay during the day and feed, mainly at night, on saltings and wet pastures in the surrounding area. Their food, ascertained from gut analyses, consists largely of grass leaves; with roots, stolons, bulbils and seeds of secondary importance. Analyses including gizzard contents much exaggerated the importance of seeds because they are retained in the gizzard for longer than softer items.
An investigation of Wigeon feeding behaviour and food preferences on salting pasture is described, using the density of the birds' droppings on different vegetation zones to assess usage, and faecal analysis to determine the composition of the selected diet. The technique of faecal analysis is discussed in relation to feeding studies on grazing wildfowl.
Disturbance is a very important factor affecting the availability of feeding habitat, and this can mask the birds' food preferences. Early in the winter, Wigeon select Puccinellia maritima in preference to Agrostis stolonifera and Festuca rubra. They do this initially by selecting the broad zone in which they feed, by selecting feeding sites within zones, and particular plant species from a mixed sward. The birds are more selective when feeding in less preferred zones. The mechanisms and reasons for food selection are discussed in relation to characteristics of the habitat and of the plants. It is concluded that the nutritional value of the plants is important in determining the birds' preference, but that other factors also play a part.
Wigeon are flexible in their feeding habits and are increasingly found on inland habitats. They are adaptable in using new roosts, and in modifying their behaviour in response to changes in food supply and changes in disturbance pressures.     

Towed-float satellite telemetry tracks large-scale movement and habitat connectivity of myliobatid stingrays

Batoids are important mesopredators whose high mobility and extensive migrations can link seemingly distant food webs in coastal ecosystems. Despite this recognition, our knowledge of the movement patterns of many species is limited due to the logistical challenge of tracking these animals on multiple scales. Smart Positioning or Temperature (SPOT) satellite-linked transmitters allow for precise, multi-scale tracking of species that regularly use surface waters. To date, SPOTs have been predominantly used on sharks, with only a single application to a batoid. Given the epipelagic nature of myliobatid stingrays, we examined the potential for towed-float SPOT transmitters to monitor large-scale movements of two representative species: the Cownose Ray (Rhinoptera bonasus; n?=?15) and Spotted Eagle Ray (Aetobatus narinari; n?=?9). Tracking data identified several consistent outmigration patterns of Cownose Rays along the Mississippi-Alabama shelf and seasonal variation in movement rates along barrier island habitats. We also documented sex-related differences in movement rates and habitat use of Spotted Eagle Rays along the Bermuda platform, where males exhibited significantly higher movement rates than females and more transient behavior between inshore lagoons and outer coral reefs. Both Cownose and Spotted Eagle Rays were shown to exhibit connectivity among several habitat types along continental shelves in their respective locales, demonstrating future challenges to the management of these species over large spatial scales. While reductions in tag size and improved tethering techniques would undoubtedly broaden the applicability of towed-float satellite telemetry to other species and sizes, our work highlights the strong potential for this technology to provide insights into the spatial ecology and habitat use of myliobatid rays.     

Habitat selection of three chrysomelid species associated with Rumex spp.

Summary Habitat selection of three chrysomelid beetles feeding on the Rumex plants was studied in relation to the ecological requirements of the three species and the habitat characteristics arising in their unstable and often unpredictable environment. The different ecological requirements and bionomic characteristics of the three chrysomelids were associated not only with their differing degrees of feeding specialization; they also influenced habitat selection. For example, the small body size and lower food demands of Mantura clavareaui, which is a feeding specialist, allowed it to exploit any habitat, irrespective of habitat size and duration. The other specialist, Gastrophysa atrocyanea, selected larger habitats because of the relatively brief lifespan of its adults after overwintering, its reduced mortality, and greater food demand. On the other hand, Galerucella vittaticollis, which is a multivoltine, general feeder, selected the habitat that lasted longer, rather than one that was larger. This species' life cycle is not synchronized with Rumex phenology, but its adults are long-lived and it has a flexible life cycle. The different patterns in habitat selection among these three chrysomelids prevented serious overlapping of their habitats; thus, the habitat overlapping of 2 or 3 species was 34.62%, that of all 3 species 3.85%. Most of the habitats utilized by Gastrophysa, however, overlapped those of the other two species, because Gastrophysa's habitat utilization range was the narrowest of the three. In Mantura, the degree of overlap with the other two species was lowest because this beetle had the broadest range of habitat utilization. On the other hand, Galerucella adjusted the temporal, rather than the spatial coordinates of its habitat usage when it occupied habitats where the other two specialists were also present. Galerucella, unlike the other two species, is multivoltine. Consequently, it was able to coexist in habitats occupied by the others by exploiting the host plants at times when the other species were numerically few, or even absent. No direct interspecific competition among adults of the three species was observed. Their different patterns of habitat selection created by their different responses to available food allowed them to coexist on Rumex without direct competition.     

Habitat partitioning and antagonistic behaviour amongst the birds of a West African scrub and plantation plot

A study was made of feeding patterns and antagonistic behaviour amongst 11 common bird species frequenting an abandoned rubber plantation and scrub plot in southern Nigeria.
The examination of feeding patterns involved a comparison of foraging habits and an analysis of the use made by each species of the major vertical and horizontal subdivisions of the habitat. Two species of muscicapid flycatchers showed a striking similarity, both in foraging habits and their use of the major habitat zones. In general, however, species with otherwise similar foraging habits were found to feed in habitat zones which were spatially separated.
A number of these latter species showed antagonistic reactions to one another. However, unlike most reported instances of such behaviour in birds, neither species in the pairs we observed played a consistently dominant role. Dominance was usually shown by whichever individual made most use, for feeding purposes, of the encounter zone.
Under these circumstances it seems possible that interspecific antagonism allows species to adjust to local variations in habitat structure and to capitalise on the temporary absence of potential competitors. In which case it is more appropriate to regard this type of behaviour as an important component in the process of habitat partitioning, rather than to dismiss it as an activity which will ultimately be rendered redundant in the course of evolution.     

Vertical movements through subsurface stream sediments by benthic macroinvertebrates during experimental drying are influenced by sediment characteristics and species traits

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Low Genetic Diversity and Low Gene Flow Corresponded to a Weak Genetic Structure of Ruddy-Breasted Crake (<Emphasis Type="Italic">Porzana fusca</Emphasis>) in China

The Ruddy-breasted Crake (Porzana fusca) is an extremely poorly known species. Although it is not listed as globally endangered, in recent years, with the interference of climate change and human activities, its habitat is rapidly disappearing and its populations have been shrinking. There are two different life history traits for Ruddy-breasted Crake in China, i.e., non-migratory population in the south and migratory population in the north of China. In this study, mitochondrial control sequences and microsatellite datasets of 88 individuals sampled from 8 sites were applied to analyze their genetic diversity, genetic differentiation, and genetic structure. Our results indicated that low genetic diversity and genetic differentiation exit in most populations. The neutrality test suggested significantly negative Fu’s Fs value, which, in combination with detection of the mismatch distribution, indicated that population expansion occurred in the interglacier approximately 98,000 years ago, and the time of the most recent common ancestor (TMRCA) was estimated to about 202,705 years ago. Gene flow analysis implied that the gene flow was low, but gene exchange was frequent among adjacent populations. Both phylogenetic and STRUCTURE analyses implied weak genetic structure. In general, the genetic diversity, gene flow, and genetic structure of Ruddy-breasted Crake were low.     

Foraging ecology of a tropical aerial feeding bird guild

The feeding ecology of the constituent members of the aerial feeding bird guild was studied in Malaya. Although numbers changed with the movements of migrants, more birds were seen feeding over forested habitats than open areas. Methods of ecological isolation were seen in morphology, flight behaviour and food selection. Seasonal changes in foraging behaviour associated with breeding and migration were found in Pacific Swallows and Barn Swallows. Migrant species were observed to mix freely with residents and no evidence was found for competitive exclusion between the two groups.     

Field and laboratory observations on the foraging and feeding techniques of blue tits (Parus caeruleus) and coal tits (P. ater) in relation to their habitats

I have tried to show (a) that results in the literature suggest that blue tits and coal tits survive better in their usual habitats of broad-leaved and conifer woods respectively; (b) that the higher mortality in the ‘wrong’ habitat may be attributed at least in part to an inability to acquire an adequate supply of food; (c) from my own and other people's field observations, that wild coal tits and blue tits use different feeding techniques; (d) from my own laboratory experiments, that each species is ‘best’ at the feeding techniques which it in general uses in the wild, and also that each species prefers to use the feeding techniques at which it is ‘best’; (e) that the feeding techniques of coal tits may be adapted to exploit the type of food supply found in conifers, while those of blue tits may be adapted for feeding in broad-leaved trees.     

Influence of lateral gradients of hydrologic connectivity on trophic positions of fishes in the Upper Mississippi River

1. Riverscapes consist of the main channel and lateral slackwater habitats along a gradient of hydrological connectivity from maximum connection in main channel habitats to minimum connection in backwaters. Spatiotemporal differences in water currents along this gradient produce dynamic habitat conditions that influence species diversity, population densities and trophic interactions of fishes. 2. We examined the importance of lateral connectivity gradients for food web dynamics in the Upper Mississippi River during spring (high flow, moderately low temperatures) and summer (low flow, higher temperatures). We used literature information and gut contents analyses to determine feeding guilds and stable isotope analysis to estimate mean trophic position of local fish assemblages. During June and August 2006, we collected over 1000 tissue samples from four habitats (main channel, secondary channels, tertiary channels and backwaters) distributed within four hydrologic connectivity gradients. 3. Mean trophic position differed among feeding guilds and seasons, with highest values in spring. Mean trophic position of fish assemblages, variability in trophic position and food chain length (maximum trophic position) of the two dominant piscivore species (Micropterus salmoides and M. dolomieu) in both seasons were significantly associated with habitat along the lateral connectivity gradient. Food chain length peaked in tertiary channels in both seasons, probably due to higher species diversity of prey at these habitats. We infer that food chain length and trophic position of fish assemblages were lower in backwater habitats in the summer mainly because of the use of alternative food sources in these habitats. 4. A greater number of conspecifics exhibited significant among‐habitat variation in trophic position during the summer, indicating that low river stages can constrain fish movements in the Upper Mississippi River. 5. Results of this study should provide a better understanding of the fundamental structure of large river ecosystems and an improved basis for river rehabilitation and management through knowledge of the importance of lateral complexity in rivers.     

Feeding behavior and differential absorption of biochemical components by the infaunal bivalve Mulinia edulis and the epibenthic Mytilus chilensis in response to changes in food regimes

We measured changes in the feeding rate and food absorption efficiency of two suspension feeding bivalves, cross-trasplanted between habitats with special emphasis on their capacity for differential absorption of biochemical components from their food supply. Mulinia edulis were moved from the intertidal zone to the subtidal zone, and Mytilus chilensis from the subtidal to the intertidal zone for a period of 7 days, and then compared with animal that had not been transplanted. Experimentally prepared diets similar to those available in the two different environments were offered to the bivalves, and their rates of feeding and differential uptake of biochemical components were determined and statistically compared. The two species did not achieve complete acclimation of their feeding behaviour during the transplant period since the highest ingestion rates for biochemical components occurred under dietary conditions that reflected their habitats of origin. Absorption efficiency showed greater acclimation than the other physiological parameters measured, indicating the capacity of these species to modulate their enzymatic-digestive activity depending on food composition. We conclude that both Mytilus and Mulinia have a certain degree of physiological plasticity in their feeding behaviour and assimilatory balance of biochemical components, being greater in Mytilus. When both species encounter ambient food conditions characteristic of their normal habitats, they show maximum values of food absorption, while under conditions where their typical diets are exchanged (Mytilus in intertidal and Mulinia in subtidal), the energy absorbed declines in each, but in ways very different between the two species. Thus, Mytilus exposed to high concentrations of low quality seston reduced the energy absorbed by 31.7% compared to its normal habitat, while Mulinia exposed to low concentrations of high-quality food reduced their energy absorption by 64%.     

SPRING MIGRATION AT THE BOSPHORUS

During observations made at the Bosphorus from 23 March to 6 April 1965, 3473 raptors were seen; the majority were Spotted/Lesser Spotted Eagles and Honey Buzzards. The migration of the main species is considered in some detail and attempts are made to correlate this with the prevailing weather. Comparisons are made with the records of observers both in spring and autumn at the Bosphorus and in spring at Gibraltar. Honey Buzzards pass in spring a month later at Gibraltar than at the Bosphorus. It is suggested that this is related to the timing of spring in the breeding areas to which these birds are returning. Notes on the observations of passerine movements and a night migration of Black Storks are also included.     

Behavioural thermoregulation of Orthopoms ornatus (Diplopoda: Spirostreptidae) in three desert habitats

Observations on feeding and locomotion of the desert millipede Orthopoms ornatus were made in three separate habitats during the summer feeding season. The habitats were Tornillo Flat in Big Bend National Park, Texas; the Jornada Validation Site of IBP/Desert Biome near Las Cruces, New Mexico; and the base of a volcanic escarpment near Albuquerque, New Mexico.
In each habitat diurnal or diel temperatures were monitored in a typical millipede microsite. Microsites included portions of a Larrea/Opuntia shrub complex (Tornillo Flat), an Ephedra shrub (Jornada Site), and a Salsola shrub (Albuquerque). Adjacent mammal-burrow temperatures were also monitored, as were soil-surface temperatures (two habitats) and air temperatures (one habitat).
Diurnal feeding and locomotion were greatest in early morning and late afternoon; nocturnal activity also occurred. Soil-surface activity generally ceased before surface temperatures reached 35^oC and began again when they cooled to about the same level. In the meantime, movement to burrows, to beneath rocks and vegetation, and to aerial portions of shrubs occurred. Additional behavioural thermoregulation was manifested by horizontal and vertical movements within shrubs, maximum air temperatures encountered being 35.5^oC.
Such behaviour is considered in light of recent studies of water balance and metabolism in this species.     

Experiments on habitat selection in voles: Implications for the inverse distribution of two common European species

Summary Several pairs of species of microtine rodents show inverse distributions or abundance. Here I determine if the inverse abundance relationship of the bank vole Clethrionomys glareolus (a forest species) and the field vole Microtus agrestis (an open field species) could be explained by habitat selection. Habitat selection was examined by choice experiments with combinations of soil and vegetation types, and with separate habitat factors. The effects of early experience and social behaviour were also studied, e.g. in a large outdoor enclosure. M. agrestis showed a stronger dependence on shelter (e.g. easily excavated soil or thick grassy vegetation) than C. glareolus, while the presence of preferred food did not affect habitat selection for either species. In both species, laboratory-bred specimens showed considerably fewer preferences. Habitat selection in subadult C. glareolus was influenced by social clumping, while territorial behaviour made more even distributions in M. agrestis.The less rigid habitat selection and weaker territorial behaviour observed in the forest species (Clethrionomys) compared with a species from temporary habitats (Microtus) is not consistent with present concepts of r- and K-selection.     

Home Range,Movement, and Distribution Patterns of the Threatened Dragonfly Sympetrum depressiusculum (Odonata: Libellulidae): A Thousand Times Greater Territory to Protect?

Dragonflies are good indicators of environmental health and biodiversity. Most studies addressing dragonfly ecology have focused on the importance of aquatic habitats, while the value of surrounding terrestrial habitats has often been overlooked. However, species associated with temporary aquatic habitats must persist in terrestrial environments for long periods. Little is known about the importance of terrestrial habitat patches for dragonflies, or about other factors that initiate or influence dispersal behaviour. The aim of this study was to reveal the relationship between population dynamics of the threatened dragonfly species Sympetrum depressiusculum at its natal site and its dispersal behaviour or routine movements within its terrestrial home range. We used a mark–release–recapture method (marking 2,881 adults) and exuviae collection with the Jolly–Seber model and generalized linear models to analyse seasonal and spatial patterns of routine movement in a heterogeneous Central European landscape. Our results show that utilisation of terrestrial habitat patches by adult dragonflies is not random and may be relatively long term (approximately 3 mo). Adult dragonflies were present only in areas with dense vegetation that provided sufficient resources; the insects were absent from active agricultural patches (p = 0.019). These findings demonstrate that even a species tightly linked to its natal site utilises an area that is several orders of magnitude larger than the natal site. Therefore, negative trends in the occurrence of various dragonfly species may be associated not only with disturbances to their aquatic habitats, but also with changes in the surrounding terrestrial landscape.     

Feeding mechanisms and feeding strategies of Atlantic reef corals

The feeding behaviour of 35 species of Atlantic reef corals was examined in the laboratory and in the field. Observations were made during the day and at night, using freshly hatched brine shrimp nauplii and finely ground, filtered fresh fish as food sources. Three feeding strategies were observed: Group I–feeding by tentacle capture only; Group II–feeding by entanglement with a mucus net or mucus filaments; Group III–feeding by a combination of tentacle capture and mucus filament entanglement. Group I included corals of the families Poritidae and Pocilloporidae which were normally expanded during both day and night. Group II included corals of the family Agaricidae which were normally expanded at night and contracted during the day. Group III included corals of the other families examined which, with the exception of Dendrogyra cylindrus , were normally expanded only at night.
Feeding responses were elicited by both chemical and tactile stimuli. A preparatory feeding posture was assumed in response to chemical stimuli and consisted of horizontal positioning of the tentacles, elevation of the oral disk to form a cone-like mouth, a wide mouth opening and secretion of mucus by the epidermis of the oral disk. Following the assumption of the preparatory feeding posture, food capture and ingestive movements were elicited by tactile stimuli. However, food capture and ingestive movements were also elicited by chemical stimuli alone in those species which were normally contracted during the day.
While expanded corals captured food with their tentacles or with mucus filaments, contracted corals were able to feed by capturing fine particulate matter with mucus filaments only and thus acted as suspension feeders. By a combination of feeding strategies, reef corals were able to feed both day and night and a wide range of potential food ranging from fine particulate matter to large zooplankton was available to them.