Comparison of the breeding habitats of Little Ringed Plover Charadrius dubius and Kentish Plover Charadrius alexandrinus on a shingle bed

The breeding habitat preferences of Kentish Plover and Little Ringed Plover were studied on a shingle bed. The location of each nest was measured as the distance to the sea wall, nearest pond and nearest path. The habitat surrounding nests was measured at radii of 0.15 m and 15 m as the proportional cover of shingle, gravel, sand, live and dead vegetation. When all variables were considered simultaneously, the differences between the habitats used by the species were related to the cover of shingle within 15 m of the nest and the distance to the sea wall. Nest sites located close to the sea wall and with high shingle cover almost always belonged to Kentish Plover, while those more distant and with low shingle cover almost always belonged to Little Ringed Plover. Kentish Plover nested in areas of newly exposed shingle, while Little Ringed Plovers used areas which had been stable for longer and hence were colonized by vegetation. This study suggests that management which maintains a high proportion of exposed substrate on shingle beds will increase their suitability for Kentish Plover.     

Predicting the population consequences of human disturbance for Ringed Plovers Charadrius hiaticula: a game theory approach

Human disturbance and its potential impacts upon bird populations are currently topical and contentious issues for conservationists. Although many studies have revealed a behavioural impact, or even direct effect on breeding success or survival, these cannot usually be extended to predict the impact on population size. Here we present a population model that allows predictions of the effect that changes in human numbers, visiting a 9-km-long section of the coastline, may have upon the size of a Ringed Plover Charadrius hiaticula population. Human disturbance affects Ringed Plovers in our study area through birds avoiding areas of high disturbance and, in addition, through the accidental trampling of a small number of nests by people walking on the beach. Using the level of human disturbance and habitat variables (which define territory quality) it is possible to predict which areas of beach are occupied and therefore the sites available to the population. Breeding success, for a given area of beach, can be predicted from habitat data. Incorporating known, density-independent, adult mortality allows the equilibrium population size to be predicted. This provides a model that predicts population size. This model is then used to predict the population that the site would support with different, hypothetical, levels of disturbance. If nest loss from human activity was prevented, for example by fencing nests, we predict the Plover population size would increase by 8%. A complete absence of human disturbance would cause a population increase of 85%. If the numbers of people were to double, we predict the population would decrease by 23%.     

Behaviour of young Ringed Plovers Charadrius hiaticula and its relationship to growth and survival to reproductive age

The behaviour, growth and survival of Ringed Plover chicks were studied in 1974 at Mestersvig, northeast Greenland, and from 1973 to 1976 at Lindisfarne, northeast England. Post-fledging survival, dispersal and recruitment were also investigated for the Lindisfarne population. Growth rates were similar in both study areas, and to those reported from other sites. A diurnal rhythm in feeding activity was more evident in the Arctic than at temperate latitudes, despite continuous daylight in the former area. This was correlated with low nocturnal temperatures and prey availability. It is concluded that food supply did not limit growth or chick survival in either study area. Brooding decreased progressively during the pre-fledging period; the relationship of brooding period to age, environmental conditions and area was investigated. The adaptations of feeding and brooding behaviour for arctic and temperate breeding Ringed Plovers are discussed. Survival from hatching to fledging varied between 40% and 60% in different areas and years, and at least 59% of birds survived from fledging to about one year old. Minimum survival from one to two years old was only 57%. but year-to-year survival of older birds was higher, that of breeding adults being at least so?;. Most birds returned to the breeding area and attempted to breed when one year old. The extent of dispersal from Lindisfarne and the wintering areas of the Lindisfarne-breeding birds are investigated.     

Breeding Population of the Ringed Plover in Britain

A census of Ringed Plovers in Britain in 1973–74 revealed a total of over 5,700 pairs, with the best concentrations in eastern England (particularly in Norfolk and Essex), the Outer Hebrides, Orkney and Shetland. Some interesting recent changes in habitat are chronicled.     

Reproductive tactics of the ringed plover Charadrius hiaticula

Reproductive tactics of ringed plovers Charadrius hiaticula were studied at three localities in SW Sweden during five seasons. The usual clutch size is four, but removal experiments showed that females can produce five eggs in succession, with similar intervals between all eggs. High predation made mean breeding success per clutch low, 6.3% of eggs resulting in fledged young. Replacement clutches were common, and many pairs laid again after rearing their first brood to fledging. Egg laying spanned three months, much longer than for other waders in this region. Between years, reproductive success varied unpredictably with time of the season, but averaged over several years, the expected success was low and similar for the different parts of the breeding season. Chicks from late clutches had similar survival and recruitment as others. Because of the long breeding season and high rate of nest failure a female may produce up to five clutches of four eggs per season, containing in total about 3.7 times her own mass. Yearly local survival of adult females and males was estimated to 84.6 and 88.6%, respectively. Ability to produce many clutches with similar expected success throughout the season favours a long reproductive period, sometimes leading to double-brooding. Possible life-history trade-offs are discussed.     

Determination of clutch-size in the Kentish Plover Charadrius alexandrinus

We studied the clutch-size distribution of Kentish Plover Charadrius alexandrinus in 1991 and 1992 and tested three hypotheses for determination of clutch-size: egg-formation ability of females, incubation ability of parents and nest predation. Variation in clutch-size was small: 71 out of 74 clutches had three eggs (coeff. var. = 7%). Females spent more time foraging (51 ± 6%) pre-laying and during egg-laying than their mates (39 ± 5%). However, we concluded that egg-formation was not constrained by food availability because 77% and 100% of clutches were initiated before the peaks of prey density and of prey mass, respectively. Furthermore, the number of clutches initiated and completed over time was unrelated to prey density. By experimentally reducing and enlarging clutches, we found that enlarged clutches of four eggs took longer to hatch (24.8 ± 0.9 days) than control clutches of three (21.6 ± 0.7 days). Eggs of enlarged clutches also lost weight more slowly during incubation in both years compared with control clutches. No difference was found in the incubation behaviour or weight loss of parents between reduced, control and enlarged clutches. We found no evidence to support the nest predation hypothesis, since neither the proportion of nests predated nor the number of chicks hatched was different between reduced, control and enlarged clutches. The results of this study are most consistent with the incubation ability hypothesis, although the parental ability hypothesis has remained untested.     

Planberingungen am Sandregenpfeifer(Charadrius hiaticula)

Zusammenfassung In den Jahren 1948–1957 wurden innerhalb einer kleinen Sandregenpfeifer-Population bei Wilhelmshaven 12 Altvögel und 41 nichtflügge Jungvögel beringt. Die Ortstreue zweier Paare betrug einmal sechs und einmal acht Jahre. Auch die Partnertreue erstreckte sich einmal über acht Jahre.Aus 92 abgelegten Eiern schlüpften 46 Junge. Das entspricht einer Erfolgsrate von 50 %. In einem Fall lag eine nicht ganz erwiesene Bigamie vor.Das Mindestalter zweier Vögel lag bei acht Jahren.Es wird außerdem über Ankunft und Abzug berichtet, sowie über Kennzeichen, Maße und Gewichte.     

Characterization of microsatellite loci isolated in Mountain Plover (Charadrius montanus)

Primers for 15 microsatellite loci were developed for Mountain Plover, a species whose distribution and abundance have been reduced drastically in the past 30 years. In a screen of 126 individuals collected from four breeding locales across the species’ range, levels of polymorphism ranged from two to 13 alleles per locus. No two loci were found to be linked, although one locus revealed significant departures from Hardy–Weinberg equilibrium. These microsatellite loci can be used in population genetic studies, ultimately aiding in management efforts for Mountain Plover. Additionally, these markers can potentially be used in studies investigating the mating system of Mountain Plover.     

Genetic and Social Monogamy – Does It Occur Without Mate Guarding in the Ringed Plover?

Among birds, waders (suborder Charadrii) show a remarkable variation in social mating systems. Their genetic mating systems are, however, less well known, especially in socially monogamous species. Here, we use DNA fingerprinting and behavioral studies to examine genetic parentage and male mate guarding in the ringed plover Charadrius hiaticula , a monogamous wader with biparental care. None of the putative parents was excluded as a genetic parent of the chicks attended (57 young from 21 families). Statistical resampling supported that extra-pair parentage occurs only rarely, if ever, in the ringed plover. We found no evidence for male mate guarding by close following as a paternity assurance strategy. Lack of extra-pair paternity in the ringed plover is therefore probably not a consequence of male mate guarding, but of high costs and/or low benefits from extra-pair copulations for females.     

Correcting observer effect bias in estimates of nesting success of a coastal bird,the White-fronted Plover Charadrius marginatus

Capsule A recently developed observer-effects model gives better estimates than the survival model.

Aims To compare the performance of the traditional survival model with that of an observer-effects model in estimating nesting success.

Methods We used survival data from 654 nests in a covariate-dependent extension of a maximum-likelihood estimator model to simultaneously estimate daily survival rate and observer effect on nesting success in four different sectors of a study site. Standard likelihood-ratio tests and Akaike's information criterion differences were used to compare model performances.

Results A significant (negative) observer effect was detected in one of four sectors of the study area, and was probably attributable to small mammal predators. Despite significantly higher predation risk during the laying period, there was a significant positive observer effect during the laying period, contrasting with a weak negative effect during the incubation period, suggesting that an observer's tracks around unattended nests reduced predation risk. Likelihood-ratio tests indicated a significantly better fit using the observer effects model versus the Mayfield survival model in four of six scenarios.

Conclusion The observer-effects model accounts for bias in estimates of nest survival rates, and is preferred over the survival model because the inclusion of observer effect as a variable does not over-parameterize the model.     

Adaptive variation in the foraging behaviour of Grey Plover Pluvialis squatarola and Whimbrel Numenius phaeopus

Between-site variation in the diet and foraging behaviour of a fixed-method forager, the Grey Plover Pluvialis squatarola , and a versatile forager, the Whimbrel Numenius phaeopus , was examined and compared at nine tropical and south temperate sites. Grey Plover always foraged in a run-stop-search manner but changed the emphasis of components of this behaviour in response to prey type. Whimbrel foraged tactilely or visually and readily changed foraging speed and habitat. Both species ate a variety of prey species depending on their availability. The diet of Grey Plover was dominated by small prey, polychaetes and crabs, and Whimbrel ate mostly crabs, with Whimbrel being the more specialized in prey choice. The broader diversity of prey types consumed by Grey Plover was attributed to limitations imposed by obligate visual foraging, whereas the flexible foraging behaviour of Whimbrel allowed the latter to concentrate their efforts on the most profitable prey. Grey Plover appeared to have a density upper limit, determined by their stereotyped foraging behaviour. Whimbrel densities varied greatly in response to prey type and foraging method. Foraging effort could not be predicted from measurements of instantaneous daytime energy intake rates, and reasons for the lack of this relationship are discussed.     

Studies on the ichthyo-fauna in Plover Cove Reservoir, Hong Kong: feeding and food relations

The feeding biology of the fish species in Plover Cove Reservoir, Hong Kong has been investigated with special reference to Sarotherodon mossambicus (Peters). The food spectra of various fish species were analysed and compared and the results indicated that S. mossambicus played an important role in the ecology of this reservoir since all major food sources were exploited.     

Burrowing and feeding behaviour in the rat

Little information is available on the burrowing activity of the brown rat, Rattus norvegicus (Berk.), in the field or laboratory. Three groups of rats (laboratory, hybrid and wild) were studied in a semi-natural environment. The observational area was entirely enclosed by a steel net and comprised a channel (22 m long) fed by Po river water and a terrestrial area of 50 m². The development of the burrow systems and their structure was not significantly different in the three groups of rats, and was comparable to those reported by other authors. The results suggest that the complexity of the burrow systems and pathways is connected to the population density of the rat group under study. An intense predation on freshwater molluscs was observed. A relationship was found between prey size and the probability of their being carried into the food-sites and burrows for consumption.     

Serotonin depresses feeding behaviour in ants

Feeding behaviour is a complex functional system that relies on external signals and the physiological state of the animal. This is also the case in ants as they vary their feeding behaviour according to food characteristics, environmental conditions and - as they are social insects - to the colony's requirements. The biogenic amine serotonin (5-HT) was shown to be involved in the control and modulation of many actions and processes related to feeding in both vertebrates and invertebrates. In this study, we investigated whether 5-HT affects nectar feeding in ants by analysing its effect on the sucking-pump activity. Furthermore, we studied 5-HT association with tissues and neuronal ganglia involved in feeding regulation. Our results show that 5-HT promotes a dose-dependent depression of sucrose feeding in Camponotus mus ants. Orally administered 5-HT diminished the intake rate by mainly decreasing the volume of solution taken per pump contraction, without modifying the sucrose acceptance threshold. Immunohistochemical studies all along the alimentary canal revealed 5-HT-like immunoreactive processes on the foregut (oesophagus, crop and proventriculus), while the midgut and hindgut lacked 5-HT innervation. Although the frontal and suboesophageal ganglia contained 5-HT immunoreactive cell bodies, serotonergic innervation in the sucking-pump muscles was absent. The results are discussed in the frame of a role of 5-HT in feeding control in ants.