Summer Population Research Articles

Effects of an increase in large wood on abundance and survival of juvenile salmonids (Oncorhynchus spp.) in an Oregon coastal stream

We examined the effect of an increase in large wood on the summer population size, smolt abundance, and freshwater survival of steelhead (Oncorhynchus mykiss), coastal cutthroat trout (Oncorhynchus clarki clarki), and coho salmon (Oncorhynchus kisutch). We examined these parameters for five brood years prior to the addition of wood and five brood years after in Tenmile Creek, a direct ocean tributary on the Oregon coast. Over the same time frame, a nearby reference stream, Cummins Creek, was also sampled for the same parameters. The input of large wood into Tenmile Creek resulted from a planned habitat restoration project in 1996 and an unplanned addition of wood from a winter storm the same year. Steelhead smolt abundance, steelhead freshwater survival, and coho salmon freshwater survival increased in Tenmile Creek after the input of large wood. Steelhead age-0+ summer populations and steelhead smolt populations increased in the reference stream, although steelhead freshwater survival did not. Coho salmon populations remained unchanged in the reference stream. Our results illustrate the potential shortcomings of the before-after-control-impact study design under field conditions and the potential for misinterpreting results had we employed a more modest sampling plan.

Virological Surveillance of Enteroviral Infection in Bulgaria During the Period 2001–2004

ABSTRACTThe results of virological investigations of patients with a suspect enterovirus etiology of diseases conducted in the National Reference Enterovirus Laboratory during the period 2001–2004 are presented. The epidemic outbreak of Poliomyelitis observed in March-May 2001 is given a special place in the report. Three cases of wild polio type 1 virus-associated Poliomyelitis were registered then. Wild polio type 1 virus was isolated from two patients and from two healthy children. Its North Indian origin was proved by genetic analysis of the wild polio isolates carried out in CDC-Atlanta. The epidemic outbreak of Aseptic Meningitis in summer 2001 was investigated virologically. The NREL proved that it was caused mostly by enterovirus ECHO30. This virus was isolated from clinical materials of the most patients with Aseptic Meningitis and from some healthy persons as well. That fact proved the active circulation of enterovirus ECHO30 among the Bulgarian population in summer 2001. In 2002–2004 big epidemic outbreaks weren't established. Since the epidemic outbreak of Poliomyelitis in 2001 wild polioviruses weren't isolated. A serotype diversity of enterovirus isolates without domination of certain serotype was observed. The role of some nonpolioenteroviruses in cases with an Acute Flaccid Paralyses in children under 15 years old and in some diseases of the central nervous system (Aseptic Meningitis and Meningoencephalitis) was established.

Seasonal succession and distribution of zooplankton in Yeniçağa Lake in northwestern Turkey

The zooplankton community structure in Yeniçağa Lake was studied during an eighteen-month survey between October 1997 and August 1999. Eight Cladoceran species, eight Copepoda and six dominant Rotifera taxa were identified. Sampling at Yeniçağa Lake revealed large seasonal variations in the zooplankton abundance and succession. Before September 1998, the total zooplankton abundance ranged from 1,691 to 21,557 ind./m3. The dominant zooplankton groups changed from autumn/spring to summer: rotifers first increased, followed by nauplii in May, finally cladocera and calanoid copepods were dominant in the summer months. The summer population started with Daphnia magna and D. pulex, followed by the smaller Ceriodaphnia dubia. Diaphanosoma brachiurum started building up its population in the late summer. Copepoda were mainly represented by the calanoid copepod Acanthodiaptomus denticornis between May and September 1998. Zooplankton abundance and composition in the lake changed drastically after September 1998. Zooplankton abundance was between 237 (September) and 9,766 (August) ind./m3. Huge filamentous cyanobacteria blooms coincided with the depression of the zooplankton abundance. Microzooplankton (mainly Rotifera and Nauplii) were dominant and Rotifera were mainly represented by Keratella and Filinia.

Structure and dynamics of a rainforest frog (Litoria genimaculata) population in northern Queensland

We studied a population of the rainforest frog Litoria genimaculata over a 7-year period at Birthday Creek, an upland rainforest stream in northern Queensland. Estimated population size on a 60-m transect fluctuated seasonally, decreasing to zero during most winters and reaching a maximum of over 130 during most warmer spring and summer months with an influx of young adult males. Summer population estimates were much smaller during 1990–93, coinciding with the disappearance of two sympatric species. However the L. genimaculata population subsequently recovered to pre-‘decline’ levels. Females were rarely captured along the stream so the operational sex ratio of adult frogs was strongly biased in favour of males (overall sex ratio 1 : 0.04). Sexual dimorphism in this species is extreme. The mean weight of gravid females (23.35 g) was nearly five times that of males (4.68 g) and the ratio of female SVL to male SVL was 1.65. Reproductive and fat-body condition changed seasonally, with males reaching peak reproductive condition in late spring and summer when population densities were greatest. Our data suggest that Litoria genimaculata uses Birthday Creek largely or exclusively as a reproductive habitat. The extent to which this species uses habitats away from stream environments remains to be determined.

Phenology, population ecology, and rarity of the New Zealand ribbonwood aphid, Paradoxaphis plagianthi

We measured some aspects of the population ecology of an arboreal aphid, Paradoxaphis plagianthi, that might contribute to its rarity. Models were fitted to data on the development rate and variability of solitary aphids in the laboratory, from larviposition to maturity, which were similar to those of several common European tree‐dwelling aphids. Life tables suggested that the intrinsic rate of population increase increases linearly with temperature to a maximum of 0.123/day at 20°C. Aphid colonies raised in controlled environments showed a lower rate of increase, presumably due to crowding effects. The rate of increase of field colonies was further depressed, probably reflecting the action of other background mortality factors. New data for seasonal population trends in the field matched previously published results, showing an increase in spring followed by a rapid decline and low summer populations. A caging experiment failed to detect any differences in host suitability in late spring between Plagianthus regius, the main host, and Hoheria angustifolia or Parsonsia heterophylla, which may act as “spill‐over” hosts in some circumstances. While the results do not explain the rarity of P. plagianthi, they suggest new hypotheses to target future work.

Not a one-way trip: historical distribution data for Australian plague locusts support frequent seasonal exchange migrations

An analysis of the development of infestations of the Australian plague locust (Chortoicetes terminifera) (Walker) (Orthoptera: Acrididae) from 1977–1995 in eastern Australia is presented which traces the sequence of generations and redistribution of gregarious populations through migration. Migration in this species has previously been viewed as a one-way trip, locusts reaching southern regions of the species range were thought to have no reliable means of return to the areas of summer population increase in western Queensland. However, a study of outbreaks over recent years, using new technologies for simulating and observing migratory events, suggested a pattern of exchange migrations, with northward movements in November and December.In this paper we provide further evidence of migrations to western Queensland from populations in the southern or eastern parts of the species range. Several northward or westward migrations from New South Wales, South Australia or eastern Queensland are identified from historic distribution data and supported by meteorological records. These migrations were significant in that they allowed the rapid re-establishment of gregarious populations in arid western Queensland after summer rains. The frequency of late-spring northward migrations is comparable to that of the better-known southward migrations in autumn. The evidence for previous conclusions about the source of historical plagues and the importance of spring breeding in arid southwest Queensland are re-examined in the light of these findings.

Design Methodology of Free Water Surface Constructed Wetlands

Simple criteria, guidelines and models are established for free water surface (FWS) constructed wetland selection and preliminary sizing. The analysis employs models for FWS constructed wetland design, considering simultaneously the removal requirements and the hydraulics of the system. On the basis of these models, a step-by-step methodology is developed outlining the design procedure for new and performance evaluation for existing FWS constructed wetland systems. This methodology is combined with simple equations predicting the maximum wetland capacity in summer, so as to assist designers in sizing installations in tourist areas with increased summer populations. Furthermore, this methodology is further simplified, based on sensitivity analysis of the unit area requirements for wastewaters of various strengths, and various design conditions and performance criteria. In addition, comparison of the unit area requirements of FWS constructed wetland systems, subsurface flow (SF) constructed wetland systems and stabilization pond systems for wastewaters of various strengths and design conditions, provides designers with general guidelines concerning the preliminary selection between alternative natural treatment systems in areas where the use of natural systems is favored because of their low-cost, simple operation and high removal performance.

Gender, Age, and Season at Immunization Uniquely Influence the Genetic Control of Susceptibility to Histopathological Lesions and Clinical Signs of Experimental Allergic Encephalomyelitis: Implications for the Genetics of Multiple Sclerosis

Multiple sclerosis (MS), the principal inflammatory demyelinating disease of the central nervous system (CNS), is believed to have an immunopathological etiology arising from gene-environment interactions. In this study, we examined the effect of sex, age, and season at immunization on the susceptibility of (B10.S x SJL/J) F(2) intercross mice to experimental allergic encephalomyelitis (EAE), the foremost animal model of MS. Results of logistic regression analyses suggest that female mice were more likely to exhibit CNS lesions than male mice [odds ratio (OR) = 2.28 for brain lesions; OR = 2.37 for spinal cord (SC) lesions]. Although statistically significant associations were seen between brain and SC lesions and age at the time of injection or month of injection when examined separately; these associations disappeared when controlling for sex in multiple logistic regression analyses. These results suggest that the sex of the mouse is more important in influencing the development of brain and SC lesions than was either age or month of immunization. When examining clinical disease as the endpoint, the OR for the age at immunization is 1.04, indicating that the odds of being affected increase by 4% for each increasing week of age. When controlled for age, the OR for injection in the summer months (July through September) is 1.90, suggesting that the odds of being clinically affected are 90% greater for F(2) intercross animals injected in the summercompared to those injected in the winter to spring months (February through May). In contrast to CNS lesions, the age and season at immunization significantly and independently influenced susceptibility to clinical EAE and did so equally in both males and females. Linkage analysis to eae5, the H2-linked locus controlling susceptibility to clinical disease, was performed using 6- to 12- and >12-week-old cohorts as well as summer and winter/spring cohorts of F(2) mice. Significant linkage of clinical EAE to eae5 was observed with the 6- to 12-week-old and summer populations. In contrast, linkage of clinical EAE to eae5 was not detected with the >12-week-old and winter/spring populations. These results indicate that age and seasonal effects are capable of overriding eae5-dependent genetic control of susceptibility to clinical EAE and have significant implications for the genetics of MS.

Effect of Adult Colorado Potato Beetle Density on Dispersal Under Field Conditions

Adult Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), released uniformly at densities of 2, 8, 16, and 32 beetles per plant, had an emigration rate independent of initial density per plant. The overwintered (postdiapause) and summer (prediapause) adult beetles emigrated at overall mean rates of 0.403 and 0.398 beetles over the first 4 h after release. The reduction in the mean percentage of released overwintered and summer beetles per plant over a period of 124 h after the initiation of the release followed an exponential decay model. Over that period, the emigration rate of overwintered populations changed faster than that of summer populations. The corresponding immigration rates into beetle-free areas (342.8 m2), which surrounded the RAs (37.4 m2) of the potato plots, were low. The overwintered and summer adult beetles immigrated at overall mean rates of 0.09 and 0.07 beetles over the first 4 h after release. A capture-mark-release-recapture test carried out using the eight beetles per plant density in 1998 showed that cross-contamination of the release plots was not a factor in the study.

Baseline susceptibility of the diamondback moth, Plutella xylostella (Linnaeus) to Bacillus thuringiensis Cry1A toxins in India

Toxicity of Bacillus thuringiensis Cry1A δ-endotoxins to the 6-day old larvae of 14 different field populations of the diamondback moth, Plutella xylostella (Linnaeus) collected from seven states in the country was determined by leaf dip bioassay method. Cry1Ab was two times more toxic than Cry1Ac. The median lethal concentrations, LC50 72h, varied from 0.002 to 0.386μg/ml for Cry1Ab and from 0.011 to 0.324μg/ml for Cry1Ac. The winter population of P. xylostella showed significantly lower (4-fold) susceptibility to Cry1Ab than the summer population at Hisar. The discriminating concentration of 15.8μg/ml for Cry1Ab over a 72h assay based upon LC99 for the most resistant strain is proposed for the routine monitoring of resistance.

The ecology of Lerista labialis (Scincidae) in the Simpson Desert: reproduction and diet

This study investigated the diet and reproductive cycle of the southern sandslider skink Lerista labialis, in the dunefields of the Simpson Desert, central Australia. We dissected preserved specimens to obtain gut contents and measure gonad volume, and also live-captured animals from 1999 to 2000 to assess the impact of rainfall on population structure and body condition. This skink breeds during the austral summer. Males start spermatogenesis in July and testes volume is largest in December. Females have enlarged ovarian follicles in November and produce oviducal eggs from November to February. One or more clutches of two eggs are produced per breeding season. L. labialis specializes on termites, which represent 78% of the diet by percentage occurrence. The remaining 22% of this skink's diet comprises Hemiptera, Neuroptera and unknown prey items. Body condition, and probably increased reproduction and juvenile survival, were higher in 2000 (wet year) than 1999 (relatively dry year); proportion of juveniles also increased in the population in autumn, winter and summer 2000 compared to the previous year. Late rainfall in autumn 2000 may have triggered these demographic changes by increasing prey accessibility. Long-term research is required into growth rates, longevity and inter-annual population dynamics of L. labialis to fully evaluate its life history strategy.

Algal Blooms in Surface Waters of the Sinop Bay in the Black Sea, Turkey

During the investigation period of August-1995 and July-1996, 22 algal species reached numerical densities exceeding 1.0x10 cells LG and it has been produced 17 mono-specific blooms by 11 of them reached 5 1 values of the order of 1.0×10 cells LG (one of them exceeding 1.0×10 cells LG ) in surface waters of the Sinop 6 1 7 1 Bay. A monthly average of cell number has been estimated as 7.1×10 cells LG in the surface waters. In the 6 1 diatom communities, subsequent blooms were dominated by Nitzschia longissima (5.2×10 cells LG ) 6 1 and Cheatoceros danicum (2.7×10 cells LG ) in January, Ditylum brightwelli (7.6 × 10 cells LG ) in March, 6 1 5 1 Pseudo-nitzschia delicatissima (9.0×10 cells LG ) in April, Cylindrotheca closterium (7.4×10 cells LG ) in early 7 1 6 1 July, Rhizosolenia calcar-avis (1.7×10 cells LG ) and Pseudo-nitzschia pungens (1.2×10 cells LG ) in late 6 1 6 1 July and mid-August. Subsequent blooms in the dinoflagellate communities were dominated by Heterocapsa triquedra (1.0×10 cells LG ) and Protoperidinium depressum (1.0×10 cells LG ) in March , 6 1 5 1 Protoperidinium granii (4.8×10 cells LG ) and Scripsiella trochoidea (7.8×10 cells LG ) in June, 5 1 5 1 Prorocentrum balticum (9.0×10 cells LG ) and Prorocentrum compressum (4.6×10 cells LG ) in mid-July, 6 1 5 1 Gonyaulax polyedra (1.4×10 cells LG ) in June, Prorocentrum micans (7.2×10 cells LG ), 5 1 5 1 Prorocentrum minimum, Protoceratium aerolatum, Protoperidinium longipes (2.0×10 cells LG ) in 5 1 mid-August and Prorocentrum aporum (1.0×10 cells LG ) in December. The highest cell numbers of 6 1 prymnesiophyte Emiliania huxleyi (5.9×10 cells LG ) was observed in mid-July. Results showed that the 6 1 declines of diatoms were followed by increases of dinoflagellates. Dinoflagellates began to increase in late-March, reached a maximum in Mid-July and gradually declined towards October. In contrast to the diatom, dinoflagellates dominated mid-spring, late summer and mid-winter populations, dinoflagellate blooms showed more pronounced in late spring and mid-summer. The mean of cell numbers of total phytoplankton in surface waters was high in April (3.4×10 cells LG ) and July (1.3×10 cells LG ), while was low in February 7 1 7 1 (9.0×10 cells LG ), respectively. A list of excessive and potential excessive phytoplankton species together with 5 1 numerical densities were prepared. Changes in number and density of algal blooms during the year were also discussed in relation to the physico-chemical features of the water column.

Seasonal Changes in the Cold Tolerance of Eggs of the Migratory Locust, <I>Locusta migratoria</I> L. (Orthoptera: Acrididae)

The migratory locust, Locusta migratoria L., has one to four generations per year in China, overwintering as eggs in the soil. In temperate Hebei province, this species has two generations per year, known as the summer and fall generations. In this study, locust populations occurring in different seasons were compared to investigate the adaptation of eggs to a cold environment. Large seasonal variations were observed in the supercooling point (SCP) and lower lethal temperature (Ltemp50, the temperature that causes 50% mortality in a population) of locust eggs. Mean SCP values of the fall population were −26.0 ± 0.1°C, while those of the summer and postwinter populations were −22.0 ± 0.8 and −23.4 ± 0.7°C, respectively. The fall population also had significantly lower Ltemp50 values (−14.2°) than the summer (−4.8°) and postwinter populations (−6.7°C). The survival ability of eggs at different development stages was also compared; 10-d-old eggs incubated at 25°C were more cold hardy than other stages. Prechilling at 5°C was effective in increasing the cold hardiness of eggs. These results confirm that eggs of the fall population are better conditioned for overwintering. The low mortality of overwintering eggs often leads to high population density and serious crop damage in the next season or following year.

Invited review: Biological control of Eurasian watermilfoil by aquatic insects: basic insights from an applied problem

Eurasian watermilfoil (Myriophyllum spicatum) is one of North America's most troublesome exotic weeds; it has infested 45 states and three Canadian provinces and millions are spent annually on control. Three insects have been considered for the biological control of Eurasian watermilfoil and all three taxa are present in the northern US and southern Canadian provinces. The naturalized pyralid caterpillar, Acentria ephemerella, has been associated with milfoil declines in some eastern states, but rarely reaches high densities in the midwest. The native midge, Cricotopus myriophylli, also does not generally reach high densities, but deserves further study. The native milfoil weevil, Euhrychiopsis lecontei, has been associated with milfoil declines across North America. The weevil, which is highly specific to watermilfoil species, has been shown to control Eurasian watermilfoil via stem mining in laboratory, tank and mesocosm studies, as well as in several field studies. During the summer, all life stages subsist on submersed watermilfoil, and after 3-5 generations are produced, adults move to shore to overwinter in shoreline leaf litter. The milfoil weevil has an induced preference for the exotic Eurasian watermilfoil and prefers and performs better on the exotic compared to native watermilfoils. Field declines of Eurasian watermilfoil due to weevil feeding will occur with sufficient weevil density and a positive native plant community response. At many sites, weevil populations are too low to effect control. Predation by sunfish (Lepomis) is likely an important factor limiting densities of adult weevils and other herbivores. Population modeling indicates that adult reproductive lifespan and fecundity are key factors for end-of summer population densities. The weevil and perhaps the other herbivores can be useful biocontrol agents if factors limiting their density can be ameliorated. This work demonstrates that herbivory by aquatic insects can be substantial, resulting in 50-95 % reductions in plant biomass and shifts in macrophyte community structure. Furthermore, important insights on the evolution of host range and host range expansion have been gained from study of this system and a better understanding of trophic cascades in littoral zones is being developed.

Evidence for declines in populations of grassland-associated birds in marginal upland areas of Britain

Capsule We report large declines among summer populations between 1968–80 and 2000. Aim To assess changes in the status of breeding populations of birds in pastoral uplands. Methods Volunteer observers revisited 13 areas of marginal upland in Britain where Common Birds Census data were collected during 1968–80. This allowed the status of 35 bird species to be examined over about 20 years and to make a comparison between grassland-based and woodland-based species. Results For 12 species the decline in abundance was significant, particularly among passerines, such as Skylark Alauda arvensis, Wheatear Oenanthe oenanthe, Whinchat Saxicola rubetra, Yellow Wagtail Motacilla flava and Yellowhammer Emberiza citrinella, each of which declined by over 80%. Redshank Tringa totanus, Yellow Wagtail, Dipper Cinclus cinclus, Whinchat, Wheatear, Ring Ouzel Turdus torquatus and Yellowhammer were found on less than half the number of plots on which they were originally recorded. Most declining species were associated with grassland for nesting and foraging, compared to those species that increased (Wood Pigeon Columba palumbus, Pied Wagtail Motacilla alba, Carrion Crow Corvus corone, Jackdaw C. monedula and Goldfinch Carduelis carduelis) that were less specialized in their habitat requirements. Woodland or woodland edge species showed no significant change in status, suggesting that population declines among grassland species were not due to lower observer effort between recording periods. Conclusion Long-term changes to grassland ecosystems in marginal upland areas of Britain may have influenced the status of bird populations.

Dynamics of a reintroduced population of red‐legged partridges Alectoris rufa in central Italy

In order to evaluate the success of a population of red‐legged partridges Alectoris rufa reintroduced into a 33.7 km2 study area, we estimated 15 demographic parameters from 1996 to 1999 by regularly monitoring the population through winter, spring and summer mapping censuses. During the study period, late winter population and spring dispersal decreased, pair number, brood number, brood production rate, chick survival and over winter losses were stable, whereas average brood size, juvenile number, age ratio, adult spring to summer survival, late summer population, and population growth rate from spring to late summer all increased. The population showed a moderate improvement in the overall productivity, mainly related to increased production of young and to a decrease in adult mortality. The improvement in breeding performance took place, in particular, after the second year of study with the conclusion of the releasing session of reared birds.

Influence of wing loading on Colorado potato beetle flight

AbstractFlight of overwintered and summer population Colorado potato beetles,Leptinotarsa decemlineataSay (Coleoptera: Chrysomelidae), with a range of wing loadings was measured following exposure to different quality diets. Beetles fed a diet of insect-resistant foliage expressingBacillus thuringiensis tenebrioniztoxins, beetles that did not feed but consumed water, and those that were starved without access to water exhibited a lower range of wing loadings than those fed conventional foliage, but there was no corresponding increase in flight frequency. Exposing potato beetles to poor food or no food resulted in a wing-loading range of 50–140 mg/cm2compared with a range of 80–200 mg/cm2for beetles fed conventional foliage. No flight was observed when wing loadings were less than 80 mg/cm2of wing surface, presumably because of other physiological processes associated with poor nutrition and not because of wing loading per se. Overwintered and summer population beetles fed a diet of conventional potato foliage did not take off when wing loading exceeded 150 mg/cm2of supporting wing surface. Similar trade-offs between flight capacity and consumption of large meals may exist for other insects.

Cholesterol bound to hemoglobin in normal human erythrocytes: a new form of cholesterol in circulation?

Objective: To study lipid fraction that is occasionally observed in red blood cell (RBC) hemolysate (supernatants from which membranes were separated). Study design: Plasma lipid profiles, cholesterol (Ch) and phospholipids (PL) in intact RBCs, RBC membranes and hemolysates were examined in young healthy male population in winter and summer. Results: The RBC Ch and PL content was significantly higher than in membranes, both in winter and summer. The “excess” of cholesterol (associated with phospholipid) was bound to hemoglobin yielding Hb–lipid adduct (Hb–Ch), the pools in the RBC membrane remaining virtually unaltered. Levels of hemoglobin–lipid complex (Hb–Ch), which were significantly higher in winter than in summer (30% and 19% of the total Hb, respectively), positively correlated with plasma HDL cholesterol levels. Conclusion: To our knowledge, this is the first demonstration of cholesterol binding to Hb. The results suggest influence of plasma lipoprotein metabolism on the formation of Hb–Ch.

Seasonal distribution of a migratory bird: effects of local and regional resource tracking

AbstractAim We studied how local and regional abundance of a migratory passerine (the blackcap Sylvia atricapilla) track resource availability in breeding and wintering grounds, in an attempt to understand the processes underlying the distribution and regulation of migratory bird populations in summer and in winter.Location Our study was conducted in Spain. In summer, we sampled five localities representing the diversity of environmental conditions met by breeding Spanish blackcaps. In winter, we sampled eight localities in the wintering range of the species including different habitat types (forests and shrublands).Methods Our approach was based on the matching rule, a model that predicts that any local variation in resource abundance between two adjacent habitat patches should be tracked by animals through a similar variation in population abundance. Eventually, this local process should conform to abundance distributions at regional scales. We sampled two habitat patches in each locality, each one including three to five line transects, 500‐m long and 50‐m wide, where we counted blackcaps and measured vegetation structure and fruit abundance.Results During the breeding season, the abundance of blackcaps was strongly correlated with the ground cover of brambles (Rubus spp.), a bush which grows in moist sectors in Mediterranean forests and is the commonest nesting substrate of Spanish blackcaps. Both local and regional changes in bramble cover were tracked by variations in blackcap abundance. However, the rate of increase in blackcap abundance with increasing bramble cover along the Spanish gradient was lower than the one predicted under resource matching. In winter, abundance of fruiting shrubs was the best predictor of blackcap abundance, although local abundance of blackcaps not always fitted local abundance of fruits. Notwithstanding this effect, the regional pattern of abundance tracked changes in fruit availability according to the matching rule.Main conclusions Our results support the strong effect of habitat quality on the abundance distribution of blackcaps and the tracking of different key resources along the year. Together with the different degrees of resource tracking by blackcaps at local and regional scales, these results also support the view that both breeding and wintering processes have to be studied, and studies have to be conducted at the appropriate spatial scales, if we are to understand the processes underlying the abundance distribution of migratory birds.

Reproductive phenology of the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae) in the Sierra Madre Oriental, Northern Mexico

In its native habitat in northern Mexico, Anastrepha ludens (Loew) is normally bivoltine although a third generation is achieved in some years. The flies overwinter mainly in the puparial stage, emerging in January-February. These flies oviposit in the spring crop of a wild citrus, Sargentia greggii (S. Wats.). The primary population peak follows in late spring to early summer (in exceptional years, separate peaks in spring and summer). Dissection of the females demonstrated that most of the flies in the spring peak are reproductively immature, indicating emergence of new adults. Activity subsides in late summer, or at least, few flies can be trapped at this time. Then in the fall there is a resurgence of adult activity. However, in contrast to the spring peak, dissection revealed that the great majority of the fall adult females are already gravid, indicating that they are carry-overs from the early summer population, rather than new recruits. The fall adults oviposit in October-November, producing the overwintering population that will emerge as adults in January-February.