Comparative Analysis of the Gut Microbial Communities of the Eurasian Kestrel (Falco tinnunculus) at Different Developmental Stages

The gut microflora play a very important role in the life of animals. Although an increasing number of studies have investigated the gut microbiota of birds in recent years, there is a lack of research work on the gut microbiota of wild birds, especially carnivorous raptors, which are thought to be pathogen vectors. There are also a lack of studies focused on the dynamics of the gut microbiota during development in raptors. In this study, 16S rRNA gene amplicon high-throughput sequencing was used to analyze the gut microbiota community composition of a medium-sized raptor, the Eurasian Kestrel (Falco tinnunculus), and to reveal stage-specific signatures in the gut microbiota of nestlings during the pre-fledging period. Moreover, differences in the gut microbiota between adults and nestlings in the same habitat were explored. The results indicated that the Eurasian Kestrel hosts a diverse assemblage of gut microbiota. Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes were the primary phyla shared within the guts of adults and chicks. However, adults harbored higher abundances of Proteobacteria while nestlings exhibited higher abundances of Firmicutes and Actinobacteria, and consequently the majority of dominant genera observed in chicks differed from those in adults. Although no significant differences in diversity were observed across the age groups during nestling ontogeny, chicks from all growth stages harbored richer and more diverse bacterial communities than adults. In contrast, the differences in gut microbial communities between adults and younger nestlings were more pronounced. The gut microbes of the nestlings in the last growth stage were converged with those of the adults. This study provides basic reference data for investigations of the gut microbiota community structure of wild birds and deepens our understanding of the dynamics of the gut microflora during raptor development.

Diet composition of syntopically breeding falcon species Falco vespertinus and Falco tinnunculus in south-western Slovakia

The red-footed falcon and Eurasian falcon represent two syntopical falcon species. While the Eurasian falcon is considered a common and numerous species in Slovakia, the red-footed falcon population has undergone a considerable decline during the past few decades. Nowadays it nests in a single locality in Slovakia, the Sysľovské polia Special Protection Area, which forms the northern and fragmented border of the species distribution area in Europe. By analysing prey remains from 9 nests (from 1998, 2001, 2013, 2014 and 2016), we identified 433 prey items belonging to 35 taxa and 9 orders. Every year, invertebrates made up the major part of the diet spectrum, in which Calosoma auropunctatum, Tettigonia viridissima, Zabrus tenebrioides, Anisoplia aegetum and Rhizotrogus sp. were the most frequent species of prey. Of the vertebrates, Microtus arvalis was the most hunted prey species. By supplementary analysis of 21 photos, we extended our knowledge on the diet by other 6 taxa. The peak of the M. arvalis population growth in 2014 did not manifest itself in the red-footed falcon diet composition. In 1998, 2014 and 2016 we also studied the diet of a syntopical species, the Eurasian kestrel. By analysing prey remains in 22 nests, we identified 1,151 prey items belonging to 37 taxa and 7 orders. In 1998 and 2014 vertebrates predominated, especially the common vole, however in 2016 invertebrates prevailed. This fact could be a reaction to the M. arvalis population peak in 2014 and its decline in 2016. These results suggest that this variability in the foraging behaviour of the Eurasian kestrel, an opportunistic predator, during the hunting of invertebrates increases the diet similarity and overlapping of the food niche of both studied falcon species.

Monitoring of colonies and provisioning of rooks with nest material as a potential tool for stabilizing colonies and increasing nesting opportunities in the countryside. Project report

The rook is a species inhabiting open agricultural landscape whose non-active nests are also used by other bird species for nesting. It is the decline in rook colonies that has been posited as one of the reasons for decrease in the red-footed falcon (Falco vespertinus) population in Slovakia since the 1970s. During the period from 2012 till 2016, four monitorings of rook colonies were carried out in south-western Slovakia (Diakovce, Nitrianska Osada, Sokolce and Tvrdošovce). In the colony at Tvrdošovce, supporting activity involving provisioning of rooks with nest material was under way from 2014 until 2016. While the colonies at Diakovce and Nitrianska Osada have been showing a slight decrease in the number of nesting rooks, despite larger interannual differences the colony at Sokolce has been showing an upward trend. The size of the colony at Tvrdošovce has been stable since the beginning of the supporting activity. This activity had a statistically significant positive effect on the width of rook nests. In 74 cases in the studied rook colonies we have recorded nesting by three other bird species – Eurasian kestrel (Falco tinnunculus) 43.8%, western jackdaw (Corvus monedula) 39.7% and long-eared owl (Asio otus) 16.4%. In 2015 two female redfooted falcons were observed in the colony at Tvrdošovce.