Plant dispersal by teal (Anas crecca) in the Camargue: duck guts are more important than their feet

1. Migratory waterbirds are major vectors for the dispersal of aquatic plants. However, quantitative field studies of the frequency of transport are scarce, and the relative importance of internal and external transport remains unclear. 2. We quantified and compared the rates of internal and external transport of aquatic plant propagules by teal (Anas crecca) in the Camargue (southern France), inspecting the lower gut contents of birds that had been shot (n = 366) and washing birds that had been live‐trapped (n = 68) during the winters of 2006–2007 and 2007–2008. 3. Intact propagules (n = 902) of 21 plant taxa were recorded in the rectum of teal, of which 16 germinated or were shown to be viable. Intact propagules were recorded in the rectum of 20% of teal, with up to 171 propagules per individual bird. Chara oogonia were most abundant (60% of intact propagules), suggesting that small size favours internal transport. Eleocharis palustris, Juncus spp. and Potamogeton pusillus (17, 7 and 6% of intact propagules, respectively) were also very abundant. 4. Intact propagules (n = 12) of 10 plant taxa were found on the outside of live teal, and four of these taxa later germinated. Intact propagules were found on 18% of teal. No teal was found to carry more than one propagule externally. There was no difference in size between propagules transported internally and externally. 5. Teal are major dispersers of plants within the Camargue, despite being highly granivorous. Contrary to widespread assumptions in the literature, endozoochory by ducks appears to be a much more important mode of dispersal for aquatic plants than exozoochory. We found no evidence of changes in the probability of plant propagule dispersal at a landscape scale over the course of the winter, so propagule production and zoochory appear to be decoupled over time in aquatic systems.     

SOME NOTES ON THE BIRDS OF THE ISOKA DISTRICT OF THE NORTHERN PROVINCE OF NORTHERN RHODESIA

Dean, W. R. J. 1978. Moult seasons of some Anatidae in the western Transvaal. Ostrich 49:76-84.

Spurwinged Geese Plectropterus gambensis, Egyptian Geese Alopochen aegyptiacus, Yellow-billed Ducks Anas undulata, Redbilled Teal A. erythrorhyncha and Southern Pochard Netta erythrophthalma have a flightless moult mainly during the dry season, from April to August, in the western Transvaal. South African Shelduck Tadorna cana moult during October to February after breeding during July and August. The Cape Shoveller Anas smithii has two main flightless periods, April-May and October-January. Cape Teal A. capensis have been recorded in flightless moult in October, December and January.

The duration of the flightless period correlates with wing length; larger and longer winged Anatidae require proportionally more time for wing moult than do smaller and shorter winged Anatidae.

Geese and shelducks moult on large open lakes with an open shore. Ducks have been recorded flightless on lakes and dams, with or without emergent vegetation.     

Counts of selected duck species at Corner Inlet, Victoria: changes in relation to local and distant meteorological variations

Numbers of four duck species present within a study area in a tidal embayment (Corner Inlet, south-eastern Australia) were obtained between 1977 and 2002. The species involved were Chestnut (Anas castanea) and Grey (A. gracilis) Teal, Pacific Black Duck (A. superciliosa) and Australian Shelduck (Tadorna tadornoides) and counts are compared with local and distant meteorological data. Chestnut and Grey Teal were most, and Australian Shelduck least, abundant. There was considerable monthly and annual variation; generally, teal and Pacific Black Duck were most numerous in summer and autumn, whereas Shelduck peaked somewhat earlier. Peak abundance corresponded to times of higher inter-annual variation and, apart from Shelduck, abundance had significant, usually weak, negative associations with rainfall though not beyond a one season lag. Pacific Black Duck numbers showed larger, more persistent and positive association with streamflows, particularly in south-eastern Australia, whereas associations for Chestnut Teal were negative and included lags of up to seven seasons. Grey Teal counts showed few significant correlations with streamflow, and Australian Shelduck numbers showed none. Abundance in some species was negatively related to the Southern Oscillation Index in the season of the count, but for Australian Shelduck there was a positive correlation for two seasons previously. Few significant relationships occurred between abundance in Corner Inlet and other Australian waterfowl abundance measures, although annual counts at Corner Inlet were positively correlated with Victorian Summer Waterfowl Counts and negatively with wetland area obtained during East Australia Counts. To an extent, results reflect current views on species’ biologies, with birds moving into and out of a saline habitat determined by breeding conditions elsewhere. As found elsewhere, there were some relationships with meteorological variables, though strength and direction varied, perhaps reflecting species’ plasticity in responses to rain events at local or distant scale and time.     

WATERFOWL (ANATIDAE) ON IRRIGATION LAKES IN THE ORANGE FREE STATE

Geldenhuys, J. N. 1975. Waterfowl (Anatidae) on irrigation lakes in the Orange Free State. Ostrich 46:219-235.

The incidence and population size of fifteen duck species were determined on nine irrigation lakes in the Orange Free State, South Africa, during August 1972 to July 1973. Allemanskraal supported the highest average number of Egyptian Goose, South African Shelduck and Yellowbilled Duck. Redbilled Teal and Spurwinged Goose favoured Bloemhof. Cape Shoveller and Cape Teal concentrated on Kalkfontein, and Southern Pochard frequented Erfenis. The most common species were the Egyptian Goose, South African Shelduck, Yellowbilled Duck and Spurwinged Goose, in thit order according to average number of birds per count, Black Duck, Whitefaced Duck, Whistling Duck, Whitebacked Duck, Hottentot Teal, Knobbilled Duck and Maccoa Duck occurred sporadically. Relatively high seasonal population nuctuations were found in the South African Shelduck, Cape Teal, Southern Pochard and to a lesser extent in the Spurwinged Goose and Cape Shoveller.     

6. GENERAL NOTES

Stutterheim, C. J. 1982. Breeding biology of the Redbilled Oxpecker in the Kruger National Park. Ostrich 53:99-90.

The nest of the Redbilled Oxpecker Buphagus erythrorhynchus in the Kruger National Park is a natural hole in a tree where no excavation is required. No evidence of a territorial system WBS observed and only the nesting tree is defended. Mammal hair, dung, grass and rootlets are used for nesting material. The average clutch size was 2.8 eggs with a mean incubation period of 12,6 days. The average nestling period was 30 days. The Redbilled Oxpecker can raise three broods in a season of 176 days such as in the 1973/74 breeding season. The activity area of one breeding group was 7,0 km². The breeding unit consists of two to five birds with helpers of both sexes. All the birds in a group help to select a nest site, build the nest and feed the young. Only one male and one female participate in incubation. Post-hatching development was studied in 13 chicks.     

Animal movement in dynamic landscapes: interaction between behavioural strategies and resource distributions

Most ecological and evolutionary processes are thought to critically depend on dispersal and individual movement but there is little empirical information on the movement strategies used by animals to find resources. In particular, it is unclear whether behavioural variation exists at all scales, or whether behavioural decisions are primarily made at small spatial scales and thus broad-scale patterns of movement simply reflect underlying resource distributions. We evaluated animal movement responses to variable resource distributions using the grey teal (Anas gracilis) in agricultural and desert landscapes in Australia as a model system. Birds in the two landscapes differed in the fractal dimension of their movement paths, with teal in the desert landscape moving less tortuously overall than their counterparts in the agricultural landscape. However, the most striking result was the high levels of individual variability in movement strategies, with different animals exhibiting different responses to the same resources. Teal in the agricultural basin moved with both high and low tortuosity, while teal in the desert basin primarily moved using low levels of tortuosity. These results call into question the idea that broad-scale movement patterns simply reflect underlying resource distributions, and suggest that movement responses in some animals may be behaviourally complex regardless of the spatial scale over which movement occurs.     

Density-dependent ant attendance and its effects on the parasitism of a honeydew-producing scale insect,Ceroplastes rubens

The intensity of attendance by a honeydew-foraging ant, Lasuis niger, on the red wax scale insect, Ceroplastes rubens, was estimated at different manipulated densities in the field. The time that individual ants were present and the total attendance time (seconds x number of ants) of ants on scale-infested twigs significantly increased as the density of C. rubens increased, i.e. ant attendance was density dependent. To determine the effects of density dependence of ant attendance on parasitism of C. rubens by Anicetus beneficus, we measured parasitism rates in the field at different density levels of C. rubens both with ant attendance and with ants excluded. Parasitism rates were higher when ants were excluded, at each density level. Although the parasitism rate significantly deceased as scale density increased, whether or not ants attended, the difference in parasitism rate between density levels was strikingly less without ant attendance. Therefore, the density-dependent decrease of parasitism rate was more pronounced with ant attendance. Mortality not due to parasitism showed density dependence in both conditions and did not change when ants were excluded. These results indicate that attending ants reduce parasitism and that, as a consequence of the density dependence of ant attendance, the efficiency of reduction of parasitism by ants is enhanced at higher densities of C. rubens.     

Factors affecting parasite prevalence among wild bumblebees

1. Bumblebees are important pollinators in North America and are attacked by a range of parasites that impact their fitness; however, few studies have investigated the extent or causes of parasitism in North America. 2. This study used a 2‐year multi‐site survey of bumblebee parasitism to ask: (i) how common are parasitoid conopid flies and the internal parasites Crithidia bombi and Nosema bombi in Massachusetts; and (ii) what factors are correlated with parasitism? 3. Infection rates by all three parasites were higher in this study than previously documented in North America. Overall, conopids infected 0–73% of bees in each sample, C. bombi infected 0–82% of bees, and N. bombi infected 0–32%. 4. Conopid flies infected female bees more than males and intermediate‐sized bees more than large or small bees. Crithidia bombi infection rates were higher in certain bee species and sites, and exhibited a unimodal pattern of prevalence over time. Nosema bombi parasitism was higher in male than female bees. 5. Infection by N. bombi in two rare bumblebee species was higher than expected based on parasitism rates of common bee species but C. bombi infection was lower. If high prevalence of N. bombi in these bumblebee species is common, parasitism may be a potential cause of their decline. 6. Given the documented effects of these parasites, the high levels of infection may affect bee populations in Massachusetts and threaten the stability of their valuable ecosystem services.     

Interspecific interactions and co-existence in dabbling ducks: observations and an experiment

We studied the possible role of resource limitation and interspecific competition in assemblages of dabbling ducks on breeding lakes in Finland and Sweden with observational and experimental data. After initial vegetation mapping and yearly censuses of ducks in 1985–1990, we collected observational data in 1991–1994 from 28 lakes with natural populations of mallard Anas platyrhynchos and teal A. crecca. Mallard and teal co-occur over vast areas in the Holarctic and they are the only breeding dabbling ducks on many oligotrophic lakes. Both species are migratory in our study regions, teal arriving later in spring than mallards. Log-linear model analysis of observational presence/absence data revealed a positive, not a negative, association between the species. This association was independent of habitat diversity as well as of lake size. Mallard-teal interaction was also studied in a cross-over introduction experiment in 32 other lakes in two years. Wing-clipped mallards were introduced to breeding lakes before the arrival of teal to induce resource limitation and interspecific competition, hypothesized to reduce lake use by teal. The density of mallard pairs on experimental lakes was 2.9–8.0 times higher than on controls, but there was no negative response by teal to the treatment. This is the first combined observational-experimental demonstration of lack of interspecific competition in waterfowl. Our results indicate that heterospecific attraction may affect species co-existence in dabbling ducks. Received: 28 October 1996 / Accepted: 13 January 1997     

8. SHORT NOTES

Stutterheim, C. J. 1980. Moult cycle of the Redbilled Oxpecker in the Kruger National Park. Ostrich 51:107-112.

This paper describes the pattern and rate of the complete moult cycle in the Redbilled Oxpecker Buphagus er ythrorhynchus. The average duration of primary moult in adult birds was 340 days and the mean time to replace a primary feather was calculated as 34 days. The moult of the secondaries is initiated at two points, at the first secondary and at the innermost secondary. Secondary moult takes seven months. The differentiated inner secondaries moult in the normal middle/inner/outer passeriform fashion. The rectrices moulted only once annually. The two body moult cycles correspond with the moult of the differentiated inner secondaries. First-year birds undergo a partial postjuvenile feather replacement at three months of age.     

Multilocus phylogeography of Australian teals (Anas spp.): a case study of the relationship between vagility and genetic structure

Biogeographic barriers potentially restrict gene flow but variation in dispersal or vagility can influence the effectiveness of these barriers among different species and produce characteristic patterns of population genetic structure. The objective of this study was to investigate interspecific and intraspecific genetic structure in two closely related species that differ in several life‐history characteristics. The grey teal Anas gracilis is geographically widespread throughout Australia with a distribution that crosses several recognized biogeographic barriers. This species has high vagility as its extensive movements track broad‐scale patterns in rainfall. In contrast, the closely related chestnut teal A. castanea is endemic to the mesic southeastern and southwestern regions of Australia and is more sedentary. We hypothesized that these differences in life‐history characteristics would result in more pronounced population structuring in the chestnut teal. We sequenced five nuclear loci (nuDNA) for 49 grey teal and 23 chestnut teal and compared results to published mitochondrial DNA (mtDNA) sequences. We used analysis of molecular variance to examine population structure, and applied coalescent based approaches to estimate demographic parameters. As predicted, chestnut teal were more strongly structured at both mtDNA and nuDNA (Φ_ST= 0.163 and 0.054, respectively) than were grey teal (Φ_ST < 0.0001 for both sets of loci). Surprisingly, a greater proportion of the total genetic variation was partitioned among populations within species (Φ_SC= 0.014 and 0.047 for nuDNA and mtDNA, respectively) than between the two species (Φ_CT < 0.0001 for both loci). The ‘Isolation with Migration’ coalescent model suggested a late Pleistocene divergence between the taxa, but remarkably, a deeper divergence between the southeastern and southwestern populations of chestnut teal. We conclude that dispersal potential played a prominent role in the structuring of populations within these species and that divergent selection associated with ecology and life history traits likely contributed to rapid and recent speciation in this pair.     

Apparent range expansion of the Redbilled Quelea Quelea quelea in the Eastern Cape Province of South Africa

Whittington-Jones, C.A. 1997. Apparent range expansion of the Redbilled Quelea Quelea quelea in the Eastern Cape Province of South Africa. Ostrich 68 (2–4): 97–103.

Distribution records obtained from the South African Bird Atlas Project (SABAP) and from published literature show that the known distribution of Redbilled Quelea in the Eastern Cape has changed dramatically over the last century. Increased search effort following the initiation of SABAP may explain the range expansion, but changes in agricultural practice have probably been a contributing factor.     

The spatial patterns of parasitism of eumenid wasps,Anterhynchium flavomarginatum andOrancistrocerus drewseni by the miltogrammine flyAmobia distorta

1. Spatial patterns of parasitism of eumenid wasps Anterhynchium flavomarginatum and Orancistrocerus drewseni by the miltogrammine fly Amobia distorta were studied in Kyoto, Japan during 1980–1984.
2. In generations of low (<5%) and medium (5–20%) parasitism, percent parasitism per shed (the habitat of the hosts) increased as a function of host density. Conversely, in generations of high (>20%) parasitism, percent parasitism was rather constant over different host densities.
3. The spatial distributions of adult miltogrammine flies among sheds were censused in generations of low and medium parasitism. The frequency of observations of adult miltogrammine flies was higher at sheds of higher host density (aggregative behavioral response), but on the other hand, the adult miltogrammine flies distributed in an underdispersed (or regular) manner in relation to other conspecifics.
4. The spatially density independent relationship between host density and percent parasitism in generations of high parasitism was explained in relation to parasitoid dispersal from patches of high parasitoid density.

     

<Emphasis Type="Italic">Catenaria anguillulae</Emphasis> Sorokin: a Natural Biocontrol Agent of <Emphasis Type="Italic">Meloidogyne graminicola</Emphasis> Causing Root Knot Disease of Rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Summary Catenaria anguillulae parasitized and killed the eggs and second stage juveniles (J₂) of Meloidogyne graminicola under natural conditions. The percentage of infection in eggs was higher than J₂ of M.␣graminicola, which ranged between 0–50.3% and 0–18.9% in 2004 and 0–46.6% and 0–21.7% in 2005, respectively. The higher parasitism of eggs and J₂ was recorded from those fields in which plants were severely infected with M. graminicola. The degree of parasitism of eggs and J₂ by C. anguillulae varied with severity of root knot disease. The fields with a higher root gall index recorded a higher percentage of infection in eggs and J₂ of M. graminicola. In general, old galls when teased and incubated, recorded higher parasitism of eggs and juveniles than young galls.     

Phenology of Parasetigena silvestris (Diptera: Tachinidae), gypsy moth (Lymantria dispar) (Lepidoptera: Lymantriidae) larval parasitoid and its efficiency for parasitisation

Parasetigena silvestris is a univoltine, solitary, larval endoparasitoid which lays its eggs on the surface of gypsy moth larvae. Field collection of the host larvae (2nd through 5th instar) from an artificially established gypsy moth population were made to compare stage specific parasitism between larvae without and with P. silvestris tachinid eggs. The tachinid oviposition rate detected was highest in second instar larvae, and then decreased as larvae developed toward full maturity. The opposite was true for tachinid parasitoid emergence which had no emergence from second through third host instar larvae. Fourth instar gypsy moth larvae, however, experienced significantly higher parasitism by P. silvestris in the larvae with eggs than those without the eggs. The braconid wasp Cotesia melanoscelus caused significantly higher parasitism in early instar larvae with P. silvestris eggs than in those without the eggs. The tachinid prefers to lay more eggs on parasitised larvae by the braconid even though the braconid is a superior competitor to the fly during multiparasitism. Factors influencing parasitism rates by P. silvestris such as host-parasitoid synchronisation and the multiparasitism interaction with C. melanoscelus are discussed.     

Determinants of the prevalence of the cloacal cestode <Emphasis Type="Italic">Cloacotaenia megalops</Emphasis> in teal wintering in the French Camargue

Eurasian teal Anas crecca (n = 46,581) were inspected during ringing operations for the presence of the hymenolepidid cloacal cestode Cloacotaenia megalops between 1954 and 1971 while wintering in the Camargue, Southern France. These birds become infected when ingesting seed shrimps (Ostracoda) that act as intermediate hosts, largely while on migration across Western Europe. The prevalence ranged from 4% to 14% per year and increased significantly over time. This long-term trend was further supported by studying 366 teal shot in 2006–2008, for which prevalence of C. megalops was 27.6%. We found no evidence to suggest that this increase in prevalence has been caused by an increase in temperature, but eutrophication and an increase in duck densities are potential contributing factors. Adult teal were more likely to be infected than first-year birds and females more so than males, probably due to differences in diet and/or habitat use. Within a given age−sex class, heavier birds were more infected than lighter ones, suggesting low pathogenicity and a causal effect of ingestion rate. Within a year, the highest prevalence was observed in mid-winter.     

Factors influencing Cinnamon Teal nest attendance patterns

Patterns of nest attendance in birds result from complex behaviours and influence the success of reproductive events. Incubation behaviours vary based on individual body condition, energy requirements and environmental factors. We assessed nest attendance patterns in Cinnamon Teal Spatula cyanoptera breeding in the San Luis Valley of Colorado in 2016–2017 using trail and video cameras to observe behaviours throughout incubation. We evaluated the effect of temporal, life‐history and environmental covariates on the frequency and duration of incubation recesses as well as the incubation constancy. There was considerable model uncertainty among the models used to evaluate recess frequency. Recess duration varied according to the interaction between nest age and a quadratic effect of time of day, with hens on older nests taking longer recesses in the afternoon and hens on nests earlier in incubation taking longer recesses in the morning and evening. Incubation constancy decreased with higher ambient temperatures in the study area. This study provides evidence that Cinnamon Teal modify their behaviour during incubation according to the age of the nest and the time of day. These results improve our knowledge of Cinnamon Teal breeding ecology and shed light on the behaviours that fast‐lived species may use to cope with environmental factors during nesting.     

Recent speciation and elevated Z‐chromosome differentiation between sexually monochromatic and dichromatic species of Australian teals

Sex chromosomes potentially have an important role in speciation and often have elevated differentiation between closely related species. In birds, traits associated with male plumage, female mate preference, and hybrid fitness have been linked to the Z‐chromosome (females are heterogametic, ZW). We tested for elevated Z‐differentiation between two recently diverged species of Australian ducks, the sexually monochromatic grey teal Anas gracilis and the dichromatic chestnut teal A. castanea. Despite prominent morphological differences, these two species are genetically indistinguishable at both mitochondrial DNA (mean Φ_ST < 0.0001) and 17 autosomal loci (mean Φ_ST = 0.0056). However, we detected elevated Z‐differentiation (mean Φ_ST = 0.281) and tentative evidence of an island of differentiation on the Z‐chromosome. This elevated differentiation was explained by a high frequency of derived alleles in chestnut teal that were absent in grey teal, which parallels independent evidence for a gain in dichromatism from a monochromatic ancestor. Coalescent estimates of demographic history and simulations indicated that the elevated Z‐differentiation was unlikely to be explained by neutral processes, but instead supported a role of divergent selection. We discuss evidence for models of speciation with gene flow versus adaptive divergence in the absence of gene flow and find that both hypotheses are plausible explanations of the data. Overall, these teal have the weakest background differentiation documented to date for a species showing a large Z‐effect, and they are an excellent model species for studying speciation genomics and the evolution of sexual dichromatism.     

Disruption of parasitism of the California red scale (Homoptera: Diaspididae) by three ant species (Hymenoptera: Formicidae)

The relative influence of the southern fire ant, Solenopsis xyloni McCook, Argentine ant, Linepithema humile (Mayr), and native gray ant, Formica aerata (Francoeur), on parasitism of California red scale, Aonidiella aurantii Maskell, was studied in the laboratory for two parasitoids, Comperiella bifasciata Howard and Aphytis melinus DeBach. All three ant species reduced percentage parasitism by C. bifasciata and both percentage parasitism and host mutilation by A. melinus. Southern fire ant was the least disruptive and native gray ant the most disruptive. Southern fire ant removed 12% of scale from the lemons, presumably to feed on them, while the other ant species did not exhibit significant removal of scale compared to the controls. Percentage parasitism of California red scale exhibited by C. bifasciata was more than 2-fold the level exhibited by A. melinus. Percentage mutilation of California red scale, including probing and host feeding, was nearly 5-fold higher for A. melinus than C. bifasciata. Because A. melinus required a longer total host examination + oviposition period in the absence of ants than C. bifasciata and because oviposition occurs as the last act in a sequence of behaviors, disruption by the ants had a more significant negative effect on oviposition by A. melinus.     

Exploring levels of egg parasitism and variation in egg cuticular chemistry in different Clavigralla spp.

Clavigralla spp. (Hemiptera: Coreidae) are major pests of cowpea (Vigna unguiculata (L.) Walp, Fabacae), common bean (Phaseolus vulgaris L., Fabacae) and pigeon pea (Cajanus cajan L., Fabacae) in Africa. Clavigralla spp. egg parasitoids, Gryon spp. (Hymenoptera: Scelionidae), have previously been reported as potential biological control candidates. Little is known about the parasitism levels and their potential relationship with cuticular chemistry of Clavigralla spp. The aims of this study were to determine parasitism levels of Clavigralla tomentosicollis Stål (Hemiptera: Coreidae) and C. elongata Signoret (Hemiptera: Coreidae) eggs, and to explore the relationship between egg parasitism and egg cuticular chemistry. High parasitism levels were determined for C. tomentosicollis by collecting eggs from plants in mono‐cropping and multi‐cropping systems in farmers’ fields in Bénin and Kenya between April and June 2016. Three species of Clavigralla were recorded: C. tomentosicollis, C. shadabi and C. elongata. Clavigralla tomentosicollis was the most common in both countries, while C. shadabi and C. elongata were only collected in Bénin and Kenya, respectively. An egg parasitoid (Gryon sp.) was recovered from egg batches collected from both countries. In parasitism assays using Gryon sp., the incidence of parasitism was higher in C. tomentosicollis eggs than that of C. elongata. Chemical analysis by coupled gas chromatography/mass spectrometry (GC/MS) of cuticular extracts obtained from C. tomentosicollis and C. elongata eggs identified fifteen compounds including ten alkanes of which the amounts varied between the two species. We speculate that Clavigralla spp. cuticular chemistry may serve as potential host location cues for Gryon sp.