Mateusz Ledwoń

Population and individual level of masting in a fleshy-fruited tree

Masting is usually considered as a population phenomenon but it results from individuals’ reproductive patterns. Studies of individual patterns of seed production and their synchrony are essential to an understanding of the mechanisms of masting. The aim of this study was to find the relationship between population and individual levels of masting. We examined individuals’ contribution to masting, considering their endogenous cycles, interannual variability and associated weather cues, as well as inter-individual synchrony of fruit production. We studied masting of Sorbus aucuparia L., which in Europe is one of the most common trees bearing fleshy fruits and is strongly affected by a specialized seed predator. The data are 11-year measurements of fruit production of 250 individuals distributed on a 27-ha area of subalpine forest in the Western Carpathians (Poland). Population- and individual-level interannual variability of fruit production was moderate. Synchrony among individuals was relatively high for all years, but the trees were much less synchronized in heavy crop years than in years of low fruit production. Weak synchrony among trees for heavy production years suggests that the predator satiation hypothesis does not explain the observed masting behavior. Fruit production, both at individual and at population level, was highly correlated with weather conditions. However, the presence of masting cannot be fully explained by the resource-matching hypothesis either. We suggest that adverse weather conditions effectively limit fruit production, causing high inter-individual synchrony in low crop years, whereas the unsynchronized heavy crop years seem to have been affected by individually available resources.

Different trapping schemes and variable disturbance intensity do not affect hatching success of Whiskered Terns Chlidonias hybrida

Capsule In the Whiskered Tern Chlidonias hybrida, hatching success was similar at nests where both parents were caught during the same trapping session and nests where parents were caught on different days. Trapping both mates during the same session may represent an efficient approach to reduce fieldwork effort, but it should be preceded by a pilot study, confirming that it does not affect breeding success.

Brood sex ratio in expansive and non-expansive tern species in east-central Poland

Capsule Evidence from two tern species does not support the theory that species in expansion should bias their brood sex ratios towards the more dispersing sex. Aims Sex ratio theory predicts that when a species is in expansion, the sex ratio should be biased towards the more dispersing sex. We compared the sex ratio of nestlings in two closely related species of terns, characterized by different expansion rates: the White-winged Tern Chlidonias leucopterus (an expansive species) and the Black Tern Chlidonias niger (a non-expansive species). Methods The fieldwork was carried out in the valleys of the Rivers Bug and Narew in east-central Poland, from 2008 to 2014, during which time eight White-winged Tern colonies and ten Black Tern colonies were monitored. Nest inspections began around 15–20 May, when the first eggs were laid, and continued until mid-July, when the last nestlings were 7–20 days old. Results The nestling sex ratios were similar in both species, and the differences between number of females and males were not significant (White-winged Tern: 56.6% females vs. 43.4% males; Black Tern: 57.4% females vs. 42.6% males). Conclusions The lack of differences in nestling sex ratio in these species may be due to the cessation of the White-winged Terns expansion in this area or because the sex ratio is characteristic of Sternidae species, as similar results have been reported for other tern species.

Post-breeding migration of Night Herons Nycticorax nycticorax tracked by GPS/GSM transmitters

AbstractThe migratory strategy of herons is poorly understood: only that of Purple Heron has been well studied. The migratory movements of three Night Herons from the Upper Vistula Valley (Poland) were studied using a GPS/GSM-tracking system in 2012. The results document a previously unknown autumn migration strategy of Night Herons with long stopovers en route, unlike that of Purple Herons. The different migration strategies of Purple Herons and Night Herons could be due to differences in wing-loadings and foraging ecology.ZusammenfassungZugbewegungen nach der Brut von mit GPS/GSM-Transmittern ausgestatteten NachtreihernNycticorax nycticorax Nur wenig ist über die Zugstrategie von Reihern bekannt; lediglich der Purpurreiher ist diesbezüglich gut untersucht. Die Zugbewegungen von drei Nachtreihern aus dem Oberen Weichseltal (Polen, Europa) wurden 2012 mit Hilfe eines GPS/GSM-Tracking-Systems untersucht. Die Ergebnisse zeigen eine bislang unbekannte Herbstzugstrategie von Nachtreihern, mit langen Zwischenstopps auf dem Weg, die denen von Purpurreihern unähnlich ist. Die unterschiedlichen Zugstrategien von Purpur- und Nachtreihern könnten auf Unterschiede in der Flächenbelastung der Flügel und der Nahrungsökologie zurückzuführen sein.

Genetic Diversity and Population Structure of the Eurasian Whiskered Tern (Chlidonias hybrida hybrida), a Species Exhibiting Range Expansion

Abstract. Contrasting the general trend of declining Afro-Palearctic migratory bird populations, the Whiskered Tern (Chlidonias hybrida hybrida) has recently exhibited spectacular demographic expansion and range shifts across its patchy European breeding distribution. To explore population connectivity of this species, individuals sampled from four sites in France, Poland, and Ukraine (n = 78) were genotyped at six microsatellite DNA loci and one partial mitochondrial cytochrome-b gene. Genetic variation was generally high (HE = 0.47-0.67; π = 1.29-2.26). Contrasting the historical absence of significant genetic structure (ΦST = 0.061-0.027), the microsatellite data indicated strong differentiation between France and the Eastern European sites (FST = 0.067-0.098). This, coupled with evidence of two distinct genetic clusters (K = 2; ΔK = 2) corresponding to little subdivision between Poland and Ukraine, has confirmed the presence of two European Whiskered Tern subpopulations (western and eastern) characterized by stark differences in wintering distribution and seasonal migratory routes.