Michael P Schaub

MIGRATING BIRDS STOP OVER LONGER THAN USUALLY THOUGHT: AN IMPROVED CAPTURE–RECAPTURE ANALYSIS

Migrating animals often divide their journey into alternating phases of migration bouts and stopping over. For investigating many questions of migration ecology it is crucial (1) to estimate the duration of stopover phases, and (2) to test whether animals of different groups differ in their stopover behavior. Using recent advances in capture–recapture statistics, we show how total stopover duration can be estimated from capture–recapture data. The probabilities of immigration are estimated and modeled by recruitment analysis and are converted into the time the animals spent at the stopover place before capture; the probabilities of emigration are estimated and modeled by survival analysis and are converted into the time the animals spent at the stopover place after capture. The sum of the two parts is the total stopover duration. Tests for differences between groups can be addressed by an appropriate model selection procedure. Two examples of migrating passerine birds at a stopover site in Switzerland illustrate this method. Mean total stopover duration was 12.3 d for Reed Warblers and 7.1 d for Reed Buntings. This was considerably higher than values obtained by the minimum stopover duration estimation (6.0 and 4.4 d, respectively). Because of the fundamental weaknesses of the minimum stopover duration estimation, which has been widely used in migration ecology, many findings obtained by this method need to be reconsidered.

Body mass of six long-distance migrant passerine species along the autumn migration route

We analysed body mass and moult data of six passerine species along their autumn migration route from northern Europe to North Africa and derived hypothetical models of the organisation of their migration in terms of fuel store accumulation. We analysed data of 46,541 first-year birds from 34 trapping sites, sampled in a network of collaborating European and African ringing stations. After accounting for effects of time of day and size, there were marked differences between the six species examined in the change of body mass along the migration route and in the timing of moult. Garden Warblers (Sylvia borin) and Pied Flycatchers (Ficedula hypoleuca) underwent their postjuvenile moult prior to migration and increased their average body mass along the migration route. Sedge Warblers (Acrocephalus schoenobaenus) also increased body mass towards the south, but started the migration bout without further refuelling well before the Sahara and moulted mainly in the wintering grounds. Reed Warblers (Acrocephalus scirpaceus) and Whitethroats (Sylvia communis) migrated while still moulting and did not increase average body mass towards south. They accumulated the energy needed to fly over the Sahara just before it. Spotted Flycatchers (Muscicapa striata) behaved in the same way, but contrary to Reed Warblers and Whitethroats they did not accumulate much fat stores in North Africa, which might urge them to stop and fuel up regularly in the Sahara. In the course of the season average body mass of all species increased slightly, which enabled them to migrate faster. In general, average body mass of first-year birds in northern and central Europe during the migration period was comparable to that of adults during breeding. Wir analysierten Körpermassen- und Mauserdaten von sechs Singvogelarten auf dem Herbstzug entlang ihres Zugweges von Nordeuropa bis Nordafrika. Die Körpermassen von 46 541 diesjährigen Vögeln, die auf 34 Beringungsstationen im Rahmen eines internationalen Projektes gesammelt wurden, sind die Grundlage dieser Untersuchung. Neben der Entwicklung der Körpermassen entlang des Zugweges untersuchten wir den Einfluss der Mauser, des Fangdatums, der Tageszeit und der Körpergröße auf die Körpermasse. Mausernde Vögel waren schwerer als nichtmausernde mit der gleichen Fettmenge. Die Körpermasse nahm im Laufe der Saison und im Verlauf des Tages zu. Große Vögel (mit einer längeren 8. Handschwinge) waren schwerer als kleine. Gartengrasmücken (Sylvia borin) und Trauerschnäpper (Ficedula hypoleuca) wurden entlang des Zugweges kontinuierlich schwerer. Beide Arten machten die Jugendteilmauser hauptsächlich noch im Brutgebiet durch. Schilfrohrsänger (Acrocephalus schoenobaenus) wurden nach Süden ebenfalls etwas schwerer, aber sie begannen mit einem Reiseabschnitt ohne weiteren Fettaufbau schon in Mitteleuropa und mauserten ihr Kleingefieder hauptsächlich erst in Afrika. Die Körpermassen von Teichrohrsängern (Acrocephalus scirpaceus) und Dorngrasmücken (Sylvia communis) blieben nach Süden weitgehend konstant. Beide Arten lagerten die nötigen Energiereserven zum Überfliegen der Sahara erst kurz davor an. Sie trennten Jugendteilmauser und Zug nicht vollständig. Ähnlich verhielten sich Grauschnäpper (Muscicapa striata), doch im Gegensatz zu den zwei vorherigen Arten, wurden sie auch im Mittelmeergebiet nicht wesentlich fetter. Sie scheinen daher regelmässig in der Wüste zu rasten und zu fressen.

Stopover durations of three warbler species along their autumn migration route

In migrating birds, the success of migration is determined by stopover duration, the most important factor determining overall speed of migration, and fuel deposition rate. However, very little is known about stopover durations of small migrant birds, because appropriate methods for data analysis were lacking until recently. We used a new capture-recapture analysis to estimate stopover durations of 1st-year reed warblers Acrocephalus scirpaceus, sedge warblers A. schoenobaenus and garden warblers Sylvia borin at 17 stopover sites in Europe and Africa during autumn. Average stopover duration of non-moulting reed warblers was 9.5 days while moulting conspecifics stayed about twice as long. Average stopover duration of sedge warblers was 9.1 days and, in contrast to the other two species, differed between years at several sites. Garden warblers stayed 7.7 days on average. The long stopover duration of the reed warbler, resulting in slow overall migration speed, is related to its low fuel deposition rate. It can be explained by low, but predictable, food resources and an early departure during moult. Compared to the reed warbler, the stopover duration of the sedge warbler varies more between sites and probably also between years, as the supply of its preferred diet (reed aphids) is spatially and temporally unpredictable but can be superabundant. The short stopover duration of the garden warbler, leading to high overall migration speed, can be related to high fuel deposition rates, probably brought about by a change to an abundant, predictable and long-lasting fruit diet. Within species, stopover duration did not change significantly along the migration route. Hence, an increase of migration speed along the migration route, as suggested in the literature, may be caused by longer flight bouts in the south. However, it remains largely unknown which environmental and possibly endogenous factors regulate stopover duration.

To Dope or Not to Dope: Neuroenhancement with Prescription Drugs and Drugs of Abuse among Swiss University Students

Background Neuroenhancement is the use of substances by healthy subjects to enhance mood or cognitive function. The prevalence of neuroenhancement among Swiss university students is unknown. Investigating the prevalence of neuroenhancement among students is important to monitor problematic use and evaluate the necessity of prevention programs. Study aim To describe the prevalence of the use of prescription medications and drugs of abuse for neuroenhancement among Swiss university students. Method In this cross-sectional study, students at the University of Zurich, University of Basel, and Swiss Federal Institute of Technology Zurich were invited via e-mail to participate in an online survey. Results A total of 28,118 students were contacted, and 6,275 students completed the survey. Across all of the institutions, 13.8% of the respondents indicated that they had used prescription drugs (7.6%) or drugs of abuse including alcohol (7.8%) at least once specifically for neuroenhancement. The most frequently used prescription drugs for neuroenhancement were methylphenidate (4.1%), sedatives (2.7%), and beta-blockers (1.2%). Alcohol was used for this purpose by 5.6% of the participants, followed by cannabis (2.5%), amphetamines (0.4%), and cocaine (0.2%). Arguments for neuroenhancement included increased learning (66.2%), relaxation or sleep improvement (51.2%), reduced nervousness (39.1%), coping with performance pressure (34.9%), increased performance (32.2%), and experimentation (20%). Neuroenhancement was significantly more prevalent among more senior students, students who reported higher levels of stress, and students who had previously used illicit drugs. Although “soft enhancers”, including coffee, energy drinks, vitamins, and tonics, were used daily in the month prior to an exam, prescription drugs or drugs of abuse were used much less frequently. Conclusions A significant proportion of Swiss university students across most academic disciplines reported neuroenhancement with prescription drugs and drugs of abuse. However, these substances are rarely used on a daily basis and more sporadically used prior to exams.

Efficacy of a Text Message-Based Smoking Cessation Intervention for Young People: A Cluster Randomized Controlled Trial

Background Smoking prevalence remains high, particularly among adolescents and young adults with lower educational levels, posing a serious public health problem. There is limited evidence of effective smoking cessation interventions in this population. Objective To test the efficacy of an individually tailored, fully automated text messaging (short message service, SMS)–based intervention for smoking cessation in young people. Methods A 2-arm cluster randomized controlled trial, using school class as the randomization unit, was conducted to test the efficacy of the SMS text messaging intervention compared to an assessment-only control group. Students who smoked were proactively recruited via online screening in vocational school classes. Text messages, tailored to demographic and smoking-related variables, were sent to the participants of the intervention group at least 3 times per week over a period of 3 months. A follow-up assessment was performed 6 months after study inclusion. The primary outcome measure was 7-day smoking abstinence. Secondary outcomes were 4-week smoking abstinence, cigarette consumption, stage of change, and attempts to quit smoking. We used regression models controlling for baseline differences between the study groups to test the efficacy of the intervention. Both complete-case analyses (CCA) and intention-to-treat analyses (ITT) were performed. Subgroup analyses were conducted for occasional and daily smokers. Results A total of 2638 students in 178 vocational school classes in Switzerland participated in the online screening. Overall, 1012 persons met the inclusion criteria for study participation, and 755 persons (74.6%) participated in the study (intervention: n=372; control: n=383). Of the 372 program participants, 9 (2.4%) unsubscribed from the program during the intervention period. Six-month follow-up data were obtained for 559 study participants (74.0%). The 7-day smoking abstinence rate at follow-up was 12.5% in the intervention group and 9.6% in the control group (ITT: P=.92). No differences between the study groups were observed in 4-week point prevalence abstinence rates. The decrease in the mean number of cigarettes smoked per day from baseline to follow-up was higher in the intervention group than in the control group (ITT: P=.002). No differences between the groups were observed in stage of change (ITT: P=.82) and quit attempts (ITT: P=.38). The subgroup analyses revealed lower cigarette consumption in both occasional and daily smokers in the intervention group compared to the control group. Occasional smokers in the intervention group made more attempts to quit smoking than occasional smokers in the control group. Conclusions This study demonstrated the potential of an SMS text message–based intervention to reach a high proportion of young smokers with low education levels. The intervention did not have statistically significant short-term effects on smoking cessation; however, it resulted in statistically significant lower cigarette consumption. Additionally, it resulted in statistically significant more attempts to quit smoking in occasional smokers. Trial Registration International Standard Randomized Controlled Trial Number (ISRCTN): 19739792; http://www.controlled-trials.com/ISRCTN19739792 (Archived by WebCite at http://webcitation.org/6IGETTHmr).

Reasons for cannabis use: patients with schizophrenia versus matched healthy controls.

Objective: The aim of the present study was to compare self-reported reasons for cannabis use in patients with schizophrenia with those of matched healthy controls. Methods: Thirty-six stable outpatients with schizophrenia treated with atypical antipsychotics and 36 matched controls were included. They completed a questionnaire exploring 15 common reasons for use, established in other studies. Results: Overall, patients more frequently agreed with the proposed reasons for use than controls. More specifically, patients with schizophrenia more often stated that they consumed cannabis to fight boredom and to ease social contacts. Conclusions: Stable schizophrenia outpatients treated with atypicals do not use cannabis in order to reduce side-effects of medication or symptoms of their disorder. Rather, they used cannabis to overcome a feeling of social exclusion. Therefore, enhancing social participation of cannabis-using patients might be an effective strategy for reducing consumption.

DOES TAPE-LURING OF MIGRATING EURASIAN REED-WARBLERS INCREASE NUMBER OF RECRUITS OR CAPTURE PROBABILITY?

Tape-luring often is used in studies of bird migration, and the technique can strongly augment the total number of birds captured. Additional captures from tape-luring could result from increasing the capture probability of birds already at the stopover site, or from attracting birds that normally would have overflown the stopover site. We conducted an experiment in which we captured night-migrating Eurasian Reed-Warblers (Acrocephalus scirpaceus) during 32 consecutive days, using tape-luring every fourth night, on average. Based on recruitment analysis (a class of Cormack-Jolly-Seber models), average capture probability was one to four times higher on days with tape-luring. The probability that a bird was a new arrival at the stopover site varied between 50% and 85% on days with tape- luring and was almost zero on control days without luring. Because tape-luring can influence where and when migrants choose to land, answers to biological questions about migration could be compromised by data from tape-lured birds. Received 6 July 1998, accepted 15 March 1999.

Web-Based Cognitive Behavioral Self-Help Intervention to Reduce Cocaine Consumption in Problematic Cocaine Users: Randomized Controlled Trial

Background Web-based self-help programs that reduce problematic substance use are able to reach hidden consumer groups in the general population. These programs are characterized by their low treatment threshold and nonrestrictive intervention settings. They are also cost effective, making them of interest to both low-income and high-income industrialized countries with ever-increasing health costs. Objective To test the feasibility and effectiveness of an anonymous, fully automated, Web-based self-help intervention as an alternative to outpatient treatment services for cocaine users. Methods A total of 196 cocaine-using participants were recruited through various online and offline media for a randomized controlled trial. Participants in the intervention group received interactive cognitive behavioral modules and a consumption diary to reduce cocaine use, whereas participants in the control group received online psychoeducative information modules. Web-based follow-up assessments were conducted after 4 weeks, 6 weeks, and 6 months. Treatment retention was examined and compared between the intervention and control groups. Severity of cocaine dependence was the main outcome measure. Secondary outcomes were cocaine craving, depression symptoms, and alcohol and other substance use. Results This Web-based intervention attracted older and more educated participants than existing outpatient treatment programs for which cocaine is the primary substance of abuse. Participants in the intervention group showed greater treatment retention compared with the control group (P = .04). Low response rates at the follow-up assessments restricted the explanatory power of the analyses. At the follow-up assessments, the severity of cocaine dependence did not differ between the intervention and control groups (P = .75). Furthermore, there were no differences in cocaine craving, depression, or alcohol and other substance use. Using the consumption diaries, the average number of cocaine-free days per week did not change significantly, whereas the weekly quantity of cocaine used decreased equally in both groups (P = .009). Conclusions For cocaine users with low dependence severity, a fully automated Web-based cognitive behavioral self-help intervention is a feasible alternative with limited effectiveness in outpatient treatment services. However, this type of intervention may attract specific user groups that are rarely reached by existing outpatient treatment and may help them to control their cocaine consumption anonymously. Trial Registration ISRCTN93702927; http://www.controlled-trials.com/ISRCTN93702927 (Archived by WebCite at http://www.webcitation.org/6CTMM10MR)

Comparing outcomes of ‘voluntary’ and ‘quasi-compulsory’ treatment of substance dependence in Europe

Aim: This study evaluates quasi-compulsory drug treatment (QCT) arrangements for substance-dependent offenders receiving treatment instead of imprisonment in comparison to voluntary treatment within five European countries. Methods: Participants were interviewed with the European Addiction Severity Index, the ASI-crime module, questions on perception of pressure and self-efficacy, and the Readiness-to-Change Questionnaire at treatment entry and after 6, 12, and 18 months. Results: Reductions in substance use and crime as well as improvements in health and social integration were observed in QCT and voluntary treatment groups. After controlling for various factors, subjects in the QCT and the comparison group showed similar reductions in substance use and crime over time. Study retention was comparable in both groups. Conclusion: QCT is as effective as voluntary treatment provided in the same services in reducing substance use and crime.

A Pre-Post Study on the Appropriateness and Effectiveness of a Web- and Text Messaging-Based Intervention to Reduce Problem Drinking in Emerging Adults

Background Problem drinking, particularly risky single-occasion drinking (RSOD), also called “binge drinking”, is widespread among adolescents and young adults in most Western countries. Few studies have tested the effectiveness of interventions to reduce RSOD in young people with heterogeneous and particularly lower educational background. Objective To test the appropriateness and initial effectiveness of a combined, individually tailored Web- and text messaging (SMS)–based intervention program to reduce problem drinking in vocational school students. Methods The fully automated program provided: (1) online feedback about an individual’s drinking pattern compared to the drinking norms of an age- and gender-specific reference group, and (2) recurrent individualized SMS messages over a time period of 3 months. Generalized Estimating Equation (GEE) analyses were used to investigate the longitudinal courses of the following outcomes over the study period of 3 months: RSOD, alcohol-related problems, mean number of standard drinks per week, and maximum number of standard drinks on an occasion. Results The program was tested in 36 school classes at 7 vocational schools in Switzerland. Regardless of their drinking behavior, 477 vocational school students who owned a mobile phone were invited to participate in the program. Of these, 364 (76.3%) participated in the program. During the intervention period, 23 out of 364 (6.3%) persons unsubscribed from participating in the program. The GEE analyses revealed decreases in the percentage of persons with RSOD from baseline (75.5%, 210/278) to follow-up assessment (67.6%, 188/278, P<.001), in the percentage of persons with alcohol-related problems (20.4%, 57/280 to 14.3%, 40/280, P=.009), and in the mean number of standard drinks per week: 13.4 (SD 15.3) to 11.3 (SD 14.0), P=.002. They also revealed a trend toward a decrease in the mean of the maximum number of drinks consumed on an occasion: 11.3 (SD 10.3) to 10.5 (SD 10.3), P=.08. Conclusions The results show high acceptance and promising effectiveness of this interventional approach, which could be easily and economically implemented within school classes.