Tibor Csörgő, Richárd Zornánszky, Tibor Szép and Péter Fehérvári
The Common Buzzard is a widespread and abundant raptor in Europe. Recently, game keepers have argued that the buzzard population has increased in Hungary and is threatening valuable small game species. Hunting of the buzzard has been prohibited since 1933, and since 1954 it has also been protected by law, in Hungary. Here we review scientific literature on recent population changes of the species, prey composition, and anatomical constraints of foraging. We show that according to the Common Bird Monitoring Program the breeding population remained stable in 1992-2012. Because of its anatomy and its hunting techniques it is not able to hunt efficiently for valuable small game. According to studies made with different methods in different parts of Europe in the last century, most of its prey species are small mammals. Therefore, the Common Buzzard population may help sustain rodent populations, thus providing essential ecosystem services for agriculture. Game species can also occur in the diet, however the proportion is negligible and buzzards usually acquire such prey as carcasses or handicapped individuals. We found no justification in favour of lifting the hunting ban of Common Buzzards in Hungary.
The Saker Falcon is a falconid raptor species with Palearctic distribution. It has never been a common bird in Hungary, now there are cc. 220-230 nesting pairs within the country borders. Currently total world population is cc. 19 000-34 000 individuals. Its taxonomic status is complicated. Two subspecies are distinguished (Falco c. cherrug and Falco c. milvipes); however, molecular data does not support this split. Phylogeny of the species is also not clarified, similarly to closely related raptors. There are many factors threatening the population of the Saker. One of these factors is the occurrence of the hybrid falcons. By molecular investigations more data can be gained, that could be useful in practical conservation, too.
Lice (Phthiraptera) chew characteristic holes on the remiges and rectrices of Barn swallows (Hirundo rustica). The number of these holes correlate positively with the intensity of louse infestation, hence hole counts are useful to quantify lousiness. Several papers showed that lice affect both life expectancy and reproductive success of hosts. In male Barn swallows, the length of the outermost tail feathers act as a sexual signal. Females prefer long-tailed males, which have significantly fewer feather holes. In this study we sampled breeding and migrating Barn swallows and compared their louse burden, and the relationship between tail length and the number of feather holes. We found significant negative correlation between feather holes and tail length in breeding males; however, we found non-significant correlation in migrating males. We suggest that attractive males have more physical interactions (e.g. extra-pair copulation) during the breeding season, than less attractive males, hence they are more exposed to louse transmission, and therefore the difference in the infestation declines towards the end of the breeding season. However, given that migrating swallow groups include colonial and solitary breeding birds, it cannot be excluded that a potentially different louse distribution on solitary breeding birds may contribute to the results.
Part 2: distributions, summary statistics and outliers
Andrea Harnos, Tibor Csörgő and Péter Fehérvári
This paper is the second part of our bird ringing data analyses series (Harnos et al. 2015a) in which we continue to focus on exploring data using the R software. We give a short description of data distributions and the measures of data spread and explain how to obtain basic descriptive statistics. We show how to detect and select one and two dimensional outliers and explain how to treat these in case of avian ringing data.
József Gyurácz, Gábor Horváth, Tibor Csörgõ, László Bank and Sándor Palkó
Influence of macrosynoptic weather situation on the autumn migration of birds in Hungary
In the study we have examined the relation between the European macrosynoptic weather situation and the number of birds captured a day at four Hungarian ringing stations during the autumn migration. Along the research we examined the data of 32 809 individuals of 8 species using different migration strategies. Using the daily capture data at the four stations we constructed the migration diagrams for each year. We chose the migration peak days within ten-day periods and examined how these peak days or their preceding days are distributed over Péczely's macrosynoptic weather situations. Comparing the 8 bird species no significant difference in distribution of the peak days over the macrosynoptic weather situations was found (ANOVA: F7,376 = 1.81, p = 0.084). 85% of the migration peak days for all the species were connected with anticyclones, 10% with meridional cyclone / cold front situation and 5% with other cyclonic ones. The most frequent weather situation on the migration peak days was central anticyclone, which occurred in 61 cases.
Part 1: data cleaning, preparation and exploratory analyses
Andrea Harnos, Péter Fehérvári and Tibor Csörgő
Bird ringing datasets constitute possibly the largest source of temporal and spatial information on vertebrate taxa available on the globe. Initially, the method was invented to understand avian migration patterns. However, data deriving from bird ringing has been used in an array of other disciplines including population monitoring, changes in demography, conservation management and to study the effects of climate change to name a few. Despite the widespread usage and importance, there are no guidelines available specifically describing the practice of data management, preparation and analyses of ringing datasets. Here, we present the first of a series of comprehensive tutorials that may help fill this gap. We describe in detail and through a real-life example the intricacies of data cleaning and how to create a data table ready for analyses from raw ringing data in the R software environment. Moreover, we created and present here the R package; ringR, designed to carry out various specific tasks and plots related to bird ringing data. Most methods described here can also be applied to a wide range of capture-recapture type data based on individual marking, regardless to taxa or research question.
This paper is the third part of our bird ringing data analysis series (Harnos et al. 2015a, 2016a) in which we continue to focus on exploring data using the R statistical environment. Here, we give a short description of missing data patterns, then handling and visualization techniques that help simultaneously explore the data and the structure of missing values. We try to emphasize that missing data can seriously distort the results of the analyses, therefore the conclusions drawn.
This study was carried out in Hungary, in an old, unmanaged, riparian poplar-willow forest, where two invasive tree species, the green ash and the boxelder maple are presented and reproduce more effectively therefore are more abundant than the native species in the study area. There are also invasive hybrid wild grapes to be found. These invasive plants cause widespread problems in floodplain forests in Central Europe. We studied Great-spotted and Lesser-spotted Woodpeckers. We investigated the following questions: Which tree species are preferred by the foraging birds? How are the foraging birds distributed spatially between the microhabitats? Are there any differences in terms of foraging niche utilization between the two studied species? We gathered our data through weekly standard observations throughout two whole years. Based on our findings we could determine that both species preferred the less abundant native trees rather than the invasive ash and maple trees, though Lesser-spotted Woodpeckers preferred hybrid wild grapes the most. Great-spotted Woodpeckers preferred the middle heights of the trees, they also moved mainly on trunks. Lesser-spotted Woodpeckers used the thinnest branches in the canopy. Based on our results we predict that the decrease of the native tree species may create a suboptimal habitat compared to the current situation. As the studied species are the major cavity excavators, the above mentioned changes will probably have significant effects on numerous cavity dependent species.
Tibor Csörgő, Péter Fehérvári, Zsolt Karcza, Péter Ócsai and Andrea Harnos
Ornithological studies often rely on long-term bird ringing data sets as sources of information. However, basic descriptive statistics of raw data are rarely provided. In order to fill this gap, here we present the seventh item of a series of exploratory analyses of migration timing and body size measurements of the most frequent Passerine species at a ringing station located in Central Hungary (1984–2017). First, we give a concise description of foreign ring recoveries of the Thrush Nightingale in relation to Hungary. We then shift focus to data of 1138 ringed and 547 recaptured individuals with 1557 recaptures (several years recaptures in 76 individuals) derived from the ringing station, where birds have been trapped, handled and ringed with standardized methodology since 1984. Timing is described through annual and daily capture and recapture frequencies and their descriptive statistics. We show annual mean arrival dates within the study period and present the cumulative distributions of first captures with stopover durations. We present the distributions of wing, third primary, tail length and body mass, and the annual means of these variables. Furthermore, we show the distributions of individual fat and muscle scores, and the distributions of body mass within each fat score category. We present data only for the autumn migratory period since there were only 27 spring captures in the study period. We distinguish the age groups (i.e. juveniles and adults) in the analyses. Our aim is to provide a comprehensive overview of the analysed variables. However, we do not aim to interpret the obtained results, merely to draw attention to interesting patterns that may be worth exploring in detail. Data used here are available upon request for further analyses.
The breeding strategies of the White Stork changed drastically during the past decades: a decreasing number of individuals nest on traditional nest sites – trees, roofs, chimneys, whereas electricity poles are increasingly selected. Here we analysed long-term breeding data of White Storks breeding in six Hungarian counties to detect patterns in nest site preferences in Hungary. According to our results, the shift to preference for electricity poles was shown at the same rate in every county, independently from the proportion of original nest sites. After 2000, although electricity poles dominated everywhere, the proportion of nest on poles without platform increased, despite the abundance of available empty platforms. To explain this pattern, we propose that White Storks show a preference for viewpoints, thus choosing to breed as near as possible to optimal habitats, regardless of nest site types. Therefore, conservation measures concerning the nest sites of this species should include preliminary habitat analysis.