Petr Musil

Long-term changes in numbers and distribution of wintering waterbirds in the Czech Republic, 1966–2008

Capsule Of 26 species of wintering waterbirds, 18 showed an increase in numbers, five showed a decrease and two showed no change. Aim To assess long-term trends in the numbers and distribution of the 26 most abundant wintering waterbird species in the Czech Republic. Methods We used International Waterbird Census data from between 48 and 639 wetland sites which had been counted annually in the Czech Republic from 1966 to 2008. From these data long-term changes in numbers and distributions were determined. Log-linear Poisson regression analysis was used to estimate missing data using trim software. The distribution of each species was described as the ratio of the number of sites occupied by that species to the total number of sites investigated. Results Increasing trends were found for 18 species, five species were found to be declining, one species was stable and two species were found with uncertain trends. Wintering distributions (the ratio of sites occupied by a given species to the total number of sites counted) increased in 16 species and decreased in two species, broadly correlated with the species changes in numbers. Conclusion In most species changes in numbers as well as changes in distribution followed the Western Palearctic population trends. Those species which increased were mainly piscivores and included geese, ducks and gulls. Scarcer species also exhibited an increase in numbers. The changes in numbers (both positive and negative) were more frequent among species associated with running water, whereas species which showed uncertain trends were more frequently recorded on standing water, which is more affected by variable weather conditions.

Numbers of wintering waterbirds in the Czech Republic: long-term and spatial-scale approaches to assess population size

Capsule Two nationwide monitoring schemes, the International Waterbird Census (IWC) and Atlas of Wintering Birds (AWB), provide comparable estimates of national population sizes of wintering waterbirds. Differences between these estimates for several species can be explained by differences in their migratory strategy. Aims We tested whether species-specific variables, i.e. the total numbers, distribution and migration strategy affected the accuracy of wintering population estimates provided by two different monitoring schemes, the IWC and AWB. Methods Estimates of the numbers of 81 waterbird species are compared, using data from IWC (mid-January) and AWB (December, January and February) in the Czech Republic between 1982 and 1985. Log-linear Poisson regression analysis was used to estimate missing IWC data from long-term IWC data series (1966–2013) using Trends and Indices for Monitoring data software. A series of generalized linear models was estimated to analyse the effect of species-specific variables on the presence of overlap between IWC and AWB national population estimates. Results The range of numbers recorded by IWC data overlap the range of AWB numbers in 22 of the 53 investigated species recorded by both monitoring schemes. Numbers of most other species based on the IWC counts were lower when compared with those generated from AWB data and included several widespread species, e.g. White-tailed Eagle Haliaeetus albicilla and White-throated Dipper Cinclus cinclus. In contrast, population size estimates based on IWC counts were higher than those generated from AWB estimates for one species, the Ferruginous Duck Aythya nyroca. The differences between IWC and AWB estimates were significantly higher in late-departing and early-arriving migrants. There was no effect of species distribution and population size. Conclusions Based on a single-country data sample, we support the relevance of the IWC Census methodology to produce estimates of wintering waterbird numbers and to calculate 1% thresholds for waterbird species, which we use to indicate nationally important wetland sites for future conservation and protection in the Czech Republic.

Long-Term Changes in Habitat Selection of Wintering Waterbirds: High Importance of Cold Weather Refuge Sites

Abstract. Recent studies showed that climate changes shape species distribution and could cause range shifts in the flyway level of the species. Here, we demonstrated changes in species habitat selection as a response to weather severity in twelve most abundant wintering waterbird species with prevailing increase in numbers during three investigated periods (1972–1978, 1987–1993 and 2003–2009). We used wintering waterbird counts from 93 sites throughout the Czech Republic from mid-January term as the coldest period of winter when the effect of thermoregulation on wintering waterbirds distribution is most apparent. We recorded no significant changes in weather severity in three investigated periods in our study area, and hence we considered the effect of preference of cold weather refuge sites, i.e. habitats which can reduce negative effect of cold weather (running waters, urban area and extensive water surface area). We found prevailing effect of weather severity in the first period what may show thermoregulatory effects being expressed by weather severity on species habitat selection in the next period in six of the twelve investigated species (Mute Swan Cygnus olor, Common Pochard Aythya ferina, Tufted Duck Aythya fuligula, Little Grebe Tachybaptus ruficollis, Common Moorhen Gallinula chloropus and Common Coot Fulica atra). In the face of recent climate change and in spite of the increasing importance of wetlands in the Czech Republic for wintering waterbirds, the suitability of these sites for wintering is likely temperature-dependent. Thus, the preference of cold weather refuges reducing the effect of winter harshness becomes important in individual species.

Inter-Nest Variability in the Egg to Hatchling Mass Ratio in the Common Pochard Aythya ferina: Does Female Body Mass Matter?

Abstract. Offspring survival and subsequent fitness are assumed to increase with offspring size. Although the relationship between egg size and young size in birds has attracted considerable scientific attention, to our knowledge no study so far has investigated differences among nests with respect to this relationship. The aim of this study was to find out 1) whether some inter-nest variation in the egg mass — young mass relationship exists among nests of Common Pochards, and 2) whether such a variation could be attributed to the body mass of the female measured in the last 5 days of incubation. Egg mass explained a higher portion of the variability in young mass in nests of heavier females. Those females produced smaller young for eggs of a given size. We suggest a trade-off between current and future reproduction as being the evolutionary mechanism underlying the relationship between female body mass and hatchling body mass.

Density-dependent regulation of breeding success in the Red-crested Pochard Netta rufina

ABSTRACT Capsule: Numbers of breeding Red-crested Pochard Netta rufina in the Czech Republic were positively correlated with reproductive success in the previous year, yet annual productivity, declined with increasing numbers of females at the beginning of the breeding season, suggesting local limiting factors on this population. Aims: To test the hypothesis that long-term increases in numbers of a breeding population of Red-crested Pochard Netta rufina can be explained by the productivity (numbers of ducklings fledged) in the previous year. We also test for the potential adverse effect of population size on population productivity in the current year. Methods: Data from 2004 to 2016 from South Bohemia, Czech Republic, were analysed using TRends and Indices for Monitoring Data software to investigate changes in numbers of adults, numbers of females at the start of the breeding season and number of broods produced. Results: There was a significant increase in the numbers of adults and females at the beginning of each breeding season. Numbers of adults in May positively correlated with productivity (numbers of ducklings fledged) in the previous breeding season, but relative productivity (broods per adult female) in the current year was negatively correlated with females abundance at the beginning of the breeding season. Conclusions: The study identifies density-dependent regulation as a factor in the population productivity of Red-crested Pochards using intensively managed fishponds as a breeding ground.