4. NOTES ON THE BIRDS OF THE VAN RYNEVELD'S PASS IRRIGATION LAKE,GRAAFF-REINET

McLachlan, A., Woodridge, T., Schramm, M. &; Kühn, M. 1980. Seasonal abundance, biomass and feeding of shore birds on sandy beaches in the Eastern Cape, South Africa. Ostrich 51:44-52.

The numbers of birds on three Eastern Cape sandy beaches were monitored monthly over one year during 1977/78. Dominant among 17 species were the Southern Blackbacked Gull Larus dominicanus, Black Oystercatcher Haematopus moquini, Whitefronted Sandplover Charadrius marginatus and Sanderling Calidris alba. These four species made up 95% of bird numbers and their respective biomass values were 78 652, 7 695, 578 and 3 116 kJ/km shoreline. Total food consumption for these species, calculated on the basis of estimated standard metabolic rates, was 4 159 394, 521 149, 76 768 and 363 053 kJ/km respectively. Food composition and feeding behaviour are also discussed and the total quantity of intertidal macrobenthic animals consumed by birds estimated.     

1. BIRD-LIFE AT THE ORANGE RIVER MOUTH

Kalejta, B. 1993. Diets of shorebirds at the Berg River estuary, South Africa: spatial and temporal variation. Ostrich 64: 123–133.

The diets of three common migrant waders; Curlew Sandpiper Calidris ferruginea. Grey Plover Pluvialis-squatarola and Greenshank Tringa nebularia and three resident species, Blacksmith Vanellus armatus, Kittlitz's Charadrius pecuarius and Whitefronted Plovers C. marginatus, were studied at the Berg River estuary, South Africa from December 1987 to April 1989. Direct observations of feeding were combined with analyses of stomach contents, pellets and droppings. Nereid worms, Ceratonereis erythraeensis and C. keiskama, were the principal food of all species studied except Greenshanks, which fed mostly on crabs, Hymenosoma orbiculare. Despite considerable overlap in the diets of all bird species, there were differences in the size classes of nereids taken by different bird species. Visually-foraging plovers (Charadriidae) were highly selective, feeding on the largest nereids regardless of their abundance. Tactile foragers, represented by Curlew Sandpipers, were non-selective, and consumed different size-classes of worms in proportion to their abundance in the substratum. Seasonal variations in the diet of waders are linked to seasonal changes in the availability of prey species.     

Foraging activity of the sand beach isopod Scyphax ornatus Dana

Abstract

The terrestrial isopod Scyphax ornatus lives on exposed sand beaches. Adult isopods spent the daytime in burrows near the high water mark and made nightly foraging excursions over the uncovered middle beach. Hourly records of their night time distribution showed that Scyphax congregated near the water’s edge during the last 4 h of flood tide, where they fed on carrion. Insects (mostly drowned honey bees) were the main food item, but coelenterates, amphipods, crabs, and goose barnacles were also eaten. During ebb and early flood tides Scyphax occurred at low densities over the uncovered middle beach. Analysis of the distribution of large and small food items on the beach showed that by feeding during the flood tide, Scyphax exploited a rich concentration of carrion that accumulated in the swash zone and that was moved slowly up the beach by the incoming tide.     

Demography and feeding behavior of the kelp crab Taliepus marginatus in subtidal habitats dominated by the kelps Macrocystis pyrifera or Lessonia trabeculata

We studied the population and feeding ecology of the kelp crab Taliepus marginatus in subtidal kelp forests dominated by either of two morphologically different kelp species (Macrocystis pyrifera or Lessonia trabeculata) in northern Chile. The sizes and abundances of T. marginatus differed between the two kelp habitats. Kelp crabs were more abundant in the M. pyrifera forest than in the L. trabeculata forest. Size‐frequency distributions showed that juvenile and immature crabs were more common in the M. pyrifera forest than in the L. trabeculata forest, where reproductive adults predominated. The smaller crabs in the M. pyrifera habitat also consumed a higher proportion of kelp tissues than the larger crabs in the L. trabeculata habitat, which had a higher proportion of animal food in their diet. In both kelp forests, individuals of T. marginatus showed a similar pattern of nocturnal feeding over a 24‐h period, consuming more food at night than during the day. The more complex and dense forests of M. pyrifera appear to present better nursery habitats for juvenile kelp crabs than the more open and less dense forests dominated by L. trabeculata. These results suggest that the role of the two kelp habitats for T. marginatus varies during the life cycle of the kelp crabs, with M. pyrifera tending to have nursery function and L. trabeculata being more suitable as a reproductive habitat.     

Modeling foraging behavior of piping plovers to evaluate habitat restoration success

Habitat restoration projects are often deemed successful based on the presence of the target species within the habitat; however, in some cases the restored habitat acts as an ecological trap and does not help to improve the reproductive success of the target species. Understanding wildlife–habitat relationships through precise measurements of animal behavior can identify critical resources that contribute to high quality habitat and improve habitat restoration practice. We evaluated the success of a restored piping plover (Charadrius melodus) breeding habitat in New Jersey, USA. We identified the major factors influencing foraging rates, compared foraging activity budgets over 3 yr at restored and natural habitats, and explored the potential of artificial tidal ponds as a viable restoration alternative. Adult foraging rates were higher in artificial pond and ephemeral pool habitats, during low tide, and after breeding activity ended. Adult foraging rates were impeded by the presence of people and vehicles within 50 m. Chick foraging rates were highest at artificial ponds and bay shores and lowest in dunes and on sand flats. Chick foraging rates were strongly hindered by the presence of corvids and the number of people within 50 m. In addition, at artificial tidal ponds, piping plovers spent more time foraging and less time engaged in defensive behaviors (vigilance, crouching, and fleeing) compared to other potential habitats. Our findings support the hypothesis that artificial tidal ponds are a valuable, perhaps superior, foraging habitat. Future beach restoration projects should include this feature to maximize habitat quality and restoration success. © 2011 The Wildlife Society.     

Genetic structure among Charadrius plovers on the African mainland and islands of Madagascar and St Helena

Colonization of islands by long-distance dispersers has great impact on genetic diversification among populations and may spearhead speciation events. We investigated intra- and interspecific divergence in Charadrius plovers with populations on mainland Africa, Madagascar and St Helena. We analysed microsatellite loci and sequence data from four nuclear and two mitochondrial gene regions. Charadrius plovers are shorebirds with high dispersal and mobility. Our results confirmed genetic differentiation between Madagascar and mainland populations of three plover species (White-fronted Plover Charadrius marginatus, Kittlitz's Plover Charadrius pecuarius and, based on sequence data only, Three-banded Plover Charadrius tricollaris) but highlight substantial variation in levels of intraspecific divergence among the three species. Namely, the Kittlitz's Plover, a dispersive habitat generalist with a polygamous mating system, exhibited lower island–mainland differentiation (0.05% COI sequence divergence) compared with the two monogamous species, the White-fronted Plover (0.6% COI divergence) and Three-banded Plover (1.6% COI divergence). In addition, past colonization of the islands of St Helena and Madagascar by ancestors of today's Kittlitz's Plover has led to the evolution of two endemic island species, the Madagascar Plover Charadrius thoracicus and the more closely-related St Helena Plover Charadrius sanctaehelenae. We discuss the factors driving species differences in island–mainland divergence and highlight the importance of conserving genetically unique island populations and island habitats to safeguard future evolutionary potential.     

Breeding populations of Little Ringed Plover Charadrius dubius and Ringed Plover Charadrius hiaticula in the United Kingdom in 2007

Capsule: The 2007 national survey of the UK breeding population of Little Ringed Plovers shows a further spread into Scotland and Wales since the previous survey in 1984. In contrast, there has been a significant decrease in the Ringed Plover breeding population.

Aims: To provide new breeding population estimates in the UK and Great Britain for Little Ringed Plover Charadrius dubius and Ringed Plover Charadrius hiaticula in 2007 and investigate changes in breeding distribution and habitat use since 1984.

Methods: Breeding population estimates were made by combining counts of pairs from ‘key sites’ (2?×?2?km tetrads known to be occupied in/since 1984) and estimates of the numbers of pairs away from these sites based on stratified sampling. Survey periods for Little Ringed Plover: 15 April to 15 July, three visits; Ringed Plover: 15 April to 30 June, two visits.

Results: Population estimates, for 2007, of 1239 (95% confidence intervals: 1175–1311) pairs of Little Ringed Plover and 5291 (5106–5478) pairs of Ringed Plovers were calculated for Great Britain, with 5438 (5257–5622) pairs of Ringed Plover estimated in the UK. Counts of Ringed Plover at inland and coastal sites, covered in both 1984 and 2007, decreased by 83% and 53%, respectively. The Little Ringed Plover population has expanded in range northward and westward since 1984. Main habitats used in 2007 by Little Ringed Plover were inland gravel and sand (25.9%) and river shingle (17.8%); and, for Ringed Plover, coastal shingle and sand (38.5% and 13.7%, respectively) and machair plus associated habitats (23.8%) in the Outer Hebrides.

Conclusions: Between 1984 and 2007, the Little Ringed Plover breeding population in the UK increased considerably, expanding northward and westward, with increased use of river shingle habitats. During the same period Ringed Plover breeding numbers in the UK declined considerably in both coast and inland habitats, likely to be due to human disturbance and habitat change, respectively.     

Ecology of the black shore skink,Leiolopisma suteri (Lacertilia: Scincidae), in boulder beach habitats

The ecology of the nocturnal black shore skink, Leiolopisma suteri, was studied on a boulder beach at Cable Bay, Motutapu Island, for 19 months. Distributions over a stable beach (Motutapu Island) and an exposed beach (Cuvier Island) were compared, and the effects of storms on the Cable Bay population were noted. Density, aggression, thermal preference, feeding, and fat reserve fluctuations were also studied. The L. suteri population at Cable Bay has, in favourable areas, one of the highest densities (13/m²) recorded for a lizard species. Spatial distribution of this population varies between the different age classes: adults congregate in the most stable areas, whereas hatchlings are commonest in the least stable areas. Storms cause changes in the beach structure and in the spatial limits of the population.     

Spatial indicators of plant community assembly from a 453-year sand-dune chronosequence

Background : We explored evidence for spatial patterning in vegetation across a sand-dune chronosequence spanning 453 years of primary succession to test for indications of a temporal signature of niche versus neutral processes during community assembly.

Methods : The study was conducted on a series of dune-capped beach ridges located in Wilderness State Park in Emmet County of northern Lower Michigan, United States (45° 43′ N, 84° 56′ E). Nearest-neighbour survey data were subjected to species dispersion and association analyses.

Results : Both species richness and species evenness showed the classic ‘hump-shaped’ relationship across successional time, suggesting that competition is an important force in structuring this community. However, the only evidence of intra-specific aggregation occurred in the youngest dune. Older dunes displayed random spatial structure and the oldest dunes tended toward a mix of random patterns and intra-specific segregation, i.e. with nearest neighbours more likely than by chance to be inter-specific. In addition, the frequency of species having lower neighbour-species richness than expected by chance was higher in younger, not older dunes. Species with significantly low neighbour richness (based on absolute nearest neighbours) on later dunes tended to have a high proportion of nearest neighbours that were intra-specific.

Conclusions : The data provided no evidence that resident species in later succession have greater intra-specific aggregation or more niche differentiation based on horizontal niche space. The data are more consistent with theories of community assembly involving competitive equivalence and/or effects of facilitation.     

The effects of aspect and exposure on the growth of dune grasses in Cape Hatteras National Seashore

During the month of July 1974, various growth parameters were measured forUniola paniculata (sea oats) andAmmophila breviligulata (American beach grass), plants on the dunes of east- and south-facing beaches of Cape Hatteras. The data were grouped based on the exposure and aspect of dunes studied. ForUniola, height of the flowering culm, number of flowering culms/m², and the height of leaves of non-flowering plants were the most diagnostic parameters. ForAmmophila, the height of the leaves of non-flowering plants was diagnostic. Generally, theUniola plants on the foredunes were taller than those on the backdunes. Plants growing on the southfacing beach were taller than their counterparts on the east-facing beach. On the southfacing beach, the side of the dunes which faces away from the ocean had the taller plants. On the east-facing beach, the side facing the ocean tended to have taller plants. ForAmmophila, the tallest plants were on the back portions of overwash areas. The next tallest occurred on the front of overwash sites. TheAmmophila plants on the ocean side of the dunes were taller than the plants on the back side of the dunes.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, U.S.A.     

Effects of feeding on zinc and cadmium accumulation by the polychaete Neanthes arenaceodentata

Abstract

The effects of feeding on the kinetics of accumulation and depuration of ⁶⁵Zn and ¹⁰⁹Cd and on the subcellular distribution of these metals has been studied in the polychaete Neanthes arenaceodentata (Moore). Feeding increases the rate of accumulation of Zn and Cd and decreases the length of time for the metals to reach a steady state concentration in the animals. These effects can be attributed to the adsorption of metals from the medium by the algal food. Feeding does not have a marked effect on the depuration of either of the metals. Both metals are lost in a biphasic manner. The initial phase probably represents the elimination of unassimilated metals from the gut lumen.

Feeding does not dramatically alter the subcellular distribution of the metals. Zinc is found primarily in the 200 g pellet while Cd is primarily found in the cytosol associated with two Cd- binding ligand pools with apparent molecular weights of 9.7 and 5.0 kDa. The former co-elutes with purified metallothionein. The latter contains the majority of the Cd in the cytosol and is prominent in fed organisms. The use of these ligands as subcellular indicators of metal induced stress is discussed.     

Abundance and distribution of sturgeon feeding pits in a Washington estuary

Sturgeon diet and feeding habitats are notoriously difficult to document. We mapped the locations of feeding pits in Willapa Bay, Washington, to characterize estuarine habitats used by sub-adult and adult sturgeon for infaunal feeding. Monthly summer surveys of intertidal plots revealed that feeding pit density was highest in July and August, when sturgeon occupy Willapa Bay. The ephemeral nature of feeding pits and high daily densities (> 1000 pits/ha) indicated intensive sturgeon feeding over unvegetated littoral mud flats during high tide. Feeding pit density was lowest in subtidal areas, over sand (grain sizes primarily >63 μ), and at sites with dense stands of non-indigenous seagrass, Zostera japonica. Sub-adult and adult sturgeon apparently used these habitats significantly less than would be predicted based on their availability. Feeding pit formation was negatively correlated with Z. japonica shoot dry weight and positively correlated with the abundance of thalassinid shrimp burrows. Experimental removal of Z. japonica resulted in increased sturgeon feeding, but experimental removal of burrowing shrimp did not significantly affect feeding pit formation. Aquaculture activities that harden substrate and proliferation of invasive seagrass both appear to produce estuarine substrates that are unsuitable for benthic feeding by sturgeon.     

Density,diet and productivity of Long-eared Owls Asio otus in the Italian Alps: the importance of Microtus voles

Capsule Relatively large populations, feeding predominantly upon voles, were present at higher elevations.

Aims To determine the density, productivity and diet composition of Long-eared Owls breeding at higher elevations.

Methods Population census and breeding biology were investigated, and dietary analysis performed for 32 Long-eared Owl territories that were occupied over a six-year period (2000–05), in a 155 km² study area located in the Noce Valley of the central-eastern Italian Alps.

Results Territories were mainly situated at the edge of large pine forests, near large patches of grassland and/or open-structured apple orchards, at elevations ranging between 540 and 1210 m. Density varied between 10 and 15 pairs/100 km². Mean intraspecific nest spacing averaged 1727 m and territories were either solitary or clumped in loose aggregations of one to five pairs. Mean laying date was 27 March and the mean number of fledged young was 0.95 and 2.13 per territorial and successful pair, respectively. Adults and nestlings were preyed upon by Eagle Owls Bubo bubo and Common Buzzards Buteo buteo, both of them abundant in the study area. Diet was dominated by Common Voles Microtus arvalis, complemented by Apodemus mice and thrushes. Annual variations in owl density, productivity and diet breadth varied in parallel with the occurrence of Common Voles in the diet, suggesting that the owls responded numerically to the availability of their main prey. This confirms earlier analyses on other European populations, but without the marked three- to four-year cycles observed in such areas.

Conclusion The conservation status of the species in these Alpine habitats seemed currently satisfactory. However, the unregulated use of rodenticides in apple orchards and the loss of open habitats associated with land abandonment may represent long-term threats for the species in these habitats.     

Trail‐following and trail‐searching behaviour in homing of the intertidal gastropod mollusc,Onchidium verruculatum

When uncovered by the tide, Onchidium verruculatum leaves its place of hiding, grazes on the rock surface, and thèn returns to its own home. Onchidium will follow its own mucus trail, most frequently towards the origin. This behaviour explains homing when the outward path is partly or completely retraced. Sometimes, however, homing occurs without contact with the outward trail. It was observed that trails were followed more closely at low humidities than at high humidities. No evidence was found for any method of orientation other than detection of chemical trials: when displaced onto sand Onchidium tend simply to crawl in a spiral until they contact their own trail. In addition to being a safe retreat, the home provides a fixed starting point to feeding excursions : this may facilitate re‐location of preferred feeding areas.     

In situ and experimental evidence of the influence of turbulence on cell division processes of Peridinium cinctum forma westii (Lemm.) Lefèvre

Comparison of the diel variations of the wind intensity and the division rate (DR) of Peridinium cinctum forma westii (Lemm.) Lefèvre in situ reveals that the intensity of the wind blowing throughout the whole day does not affect the DR. On the other hand, a strong inhibitory effect is noticed when the wind episodes occur during the time period 18.00–02.00 h. Systematic hourly sampling and staining of Peridinium cells showed that nuclear division takes place between 23.00 and 02.00 h and is completed before cytokinesis begins. Thus the time period 18.00–02.00 h corresponds to the premitotic and mitotic phases of cell division, and the turbulence generated by the wind affects the process of nuclear division.

The relationship between water turbulence and the DR of Peridinium which was observed in Lake Kinneret (Israel) has been checked under experimental conditions. Peridinium was grown without shaking, with continuous rotary shaking and with intermittent shaking at 100 r min^-1. The specific growth rate (k), generation time (G) and mortality rate were followed and compared. The results obtained confirm the facts observed in situ and clarify some aspects. Intermittent shaking of 2 h day^-1 during the dark phase reveals the inhibitory effect of agitation on nuclear division. Continuous shaking causes a high rate of cell mortality. Shaking during the light period does not affect the division process.

The effect of turbulence on the DR of Peridinium explains why the timing of the bloom in Lake Kinneret is a function of the duration and intensity of the mixing period in the lake.     

Aspects of the biology of the euryhaline Asian cichlid,Etroplus suratensis

Synopsis Aspects of the biology of the euryhaline Asian cichlid Etroplus suratensis in a coastal lagoon of Sri Lanka were studied for a period of 15 months. Comparisons are made from the catches from the fishery of manmade, inland freshwater reservoirs. Changes in the stock structure in the sublittoral region of the lagoon indicate that recruitment takes place twice a year, during the high rainfall/low salinity periods. The feeding habits of E. suratensis were different in the two habitats. In the lagoon it fed mainly on molluscs and in the freshwater reservoirs on macrophytes. Feeding chronology based on diurnal surveys indicate that it feeds mainly during the daylight hours. The dentition of E. suratensis is adapted for both tearing and crushing (pharyngeal teeth). Distinct differences in the mean relative intestinal length between populations from the coastal lagoon and inland reservoirs were evident and these differences are correlated to their respective feeding habits. Diurnal changes in feeding activity are associated with changes in the stomach pH. The egg-diameter distribution of mature fish indicate that E. suratensis is a single spawner, that it sheds its mature eggs all at once. It is inferred that E. suratensis breeds twice a year but that an individual female is capable of spawning only once a year.     

Influence of patch size and connectivity on beach and dune species in land-uplift coasts

Background: Land-uplift beaches and adjacent dunes contribute considerably to natural diversity. In such fragmented habitat types, the size and connectivity of a habitat patch are hypothesised to strongly influence the distribution of species, particularly the most habitat-specific ones.

Aims: To test this hypothesis, our study compared the effects of habitat pattern (patch size and connectivity) and local environmental factors on the distribution and richness of beach species.

Methods: We collected extensive observational data on vegetation and environment from beach systems along a 600-km land-uplift gradient on the Baltic Sea coast. The analyses were repeated with three modelling methods to ensure that the results were independent of the selected method.

Results and conclusions: Our results indicate that patch size and connectivity influence the occurrence and richness of habitat specialists, while total beach species richness is less dependent on the habitat pattern. Patch size and connectivity are as influential on beach vegetation as local environmental drivers. Unexpectedly, largest patch size or highest connectivity does not appear to maximise species richness or the probability of species occurrence. Instead, the study highlights species-specific responses and the value of also relatively small and isolated habitat patches. Both the diverse network of habitat patches and local environmental variability should be accounted for to efficiently preserve beach species.     

Winter feeding strategies of individually marked herons

The winter feeding behaviour of individually marked herons was studied in an estuarine habitat with adjacent streams in north-east Scotland. Feeding rates in the estuary were highest around low tide, and no feeding took place 3 h before and after low tide. Feeding rates at streams were significantly lower than in the estuary, but were constant throughout the day.Individual herons fed consistently with one of the following strategies: (1) feeding in a stream only: (2) feeding in the estuary only; or (3) switching between stream and estuary. The feeding rate was measured as a basis for a comparison of the benefits of alternative feeding strategies. A comparison between the three feeding strategies showed that herons that switched between estuary and streams achieved a significantly higher food intake than birds that used a stream feeding site only. The timing of arrival on the estuary and departure from the estuary to the streams was consistent with an energy maximization hypothesis. In midwinter, switchers were significantly heavier than non-switchers.     

Temporal and areal feeding behavior of the butterflyfish,Chaetodon trifascialis,at Johnston Atoll

Synopsis The chevron butterflyfish,Chaetodon trifascialis, is found throughout the Indo-Pacific. It is a territorial, diurnal, corallivore found in close association withAcropora spp. corals. The feeding behavior of 33 individuals was studied over six seasons in three habitats.Chaetodon trifascialis spent one third of its active time feeding. However, there was much individual variation. Fish had significantly higher feeding rates during the early afternoon, and there were no significant differences in the feeding rates between the seasons. Feeding rates were significantly different between the three habitats. TheMontipora-rich habitat had the highest feeding rates (x = 10.74 bites min^-1 ± 0.87, all corals combined) and theAcropora-Montipora mixed habitat had the lowest feeding rates (x = 4.58 bites min^-1 ± 0.63, all corals combined). Females fed significantly more than males. WhileC. trifascialis had been thought to only eatAcropora spp. corals, it occasionally fed onMontipora spp. andPocillopora sp. corals whenAcropora spp. were scarce.Chaetodon trifascialis exhibited patterns predicted by foraging theory of an energy maximizer. Territory sizes were inversely related to food density and feeding rates were inversely related to intruder rates. This is a promising system for future testing of foraging strategy models.