Jerzy Romanowski

Muskrat (Ondatra zibethicus) decline after the expansion of American mink (Neovison vison) in Poland

Field survey data in Central Poland revealed that the proportion of sites inhabited by muskrats decreased from 44% to 7% over one decade. This corresponded to the decline in hunting bags of muskrat over the whole of Poland. The largest hunting harvest of muskrat was recorded in 1987/1988 (66,416 individuals), the smallest in 2007/2008 (4,567 individuals). The decline in hunting bags occurred in all regions analysed; however, it was most rapid in the north and north-east. Before the expansion of mink, which started in northern Poland at the beginning of the 1980s, muskrat densities in particular regions depended on the availability of aquatic habitats. A comparison of hunting bags of muskrat and American mink in years 2002–2008 indicated a significant negative correlation between the numbers of these two species harvested in seven regions of Poland. The negative correlation between numbers of muskrat and mink suggests that mink predation is one of the most important factors in the decline of the muskrat population in Poland.

Seasonal and habitat variation in the diet of the tawny owl (Strix aluco) in central Poland during unusually warm years

In the temperate climate zone in Europe the composition of the diet of predatory vertebrates shows evident variability between the warm and cold season. However, the recently observed climate warming can mitigate the effect of snow cover and low temperatures on the winter foraging ecology of raptors, thus affecting trophic webs in ecosystems. We analysed diet variability in the tawny owl Strix aluco, between the warm and cold seasons of four unusually warm years (as compared to reference years of 1950–2000) in two habitats (forest vs. farmland) in Central Poland. The most important prey group in the tawny owl’s diet were mammals, constituting over 80% of prey items. There were distinct diet differences between the two seasons: insectivorous mammals, birds and amphibians were caught more often during the warm season, and Muridae and Arvicolidae during the cold season. The proportion of insectivorous mammals, voles and amphibians was significantly higher in forest than in farmland. Diet diversity, analysed with rarefaction methods and expressed as the expected cumulative mammal species number for a given number of randomly sampled preyed mammals, was independent of season and higher in forest than in the agricultural habitat. We conclude that even during unusually warm years tawny owls change significantly their feeding habits between the warm and cold season. The effect of season, habitat and weather factors on diet variability in raptors are discussed.

Environmental factors affecting the densities of owls in Polish farmland during 1980–2005

During the last decades, farmland habitats in central European countries have changed significantly, seriously affecting populations of many farmland bird species. We compiled available published data on densities of three owl species, Athene noctua, Asio otus and Strix aluco collected in the Polish farmland. All results of censuses based on the playback method conducted between 1980–2005 were included in the analysis. The proportions of grassland, fields, built-up land and forest at each studied plot were estimated and used as predictors in additive models. Proportions of main land use types, extracted with the principal component analysis, explained much of the variation found in owl densities, although some of the relationships were nonlinear. In general, owl densities were found to be affected positively by a high percentage of grasslands and built-up land, and negatively by the amount of fields and forests. Little owl densities showed a significant negative trend over the study period. It seems that high prey availability is an important factor accounting for the positive relationship between grassland proportion and owl density. The significant decrease in grassland areas and increase in forest coverage that were recently recorded in Poland may thus negatively affect populations of the three owl species studied here.

Nest Construction During Autumn Display and Winter Roosting in the Tree Sparrows Passer montanus

Abstract. A study of Tree Sparrows was conducted near Warsaw, central Poland. During the breeding season, nest boxes were checked to record the presence of Tree Sparrow nests and broods. Nestlings, juveniles, and adults captured in mist nets were ringed with different combinations of colour rings to identify their age during visual observations in the autumn sexual display period. Before the autumn display, breeding nests were dyed in order to identify nest material added during the autumn display period. In winter, nest boxes were inspected to catch the birds roosting in them at night. The study was conducted in optimal and marginal habitat types. In the optimal habitat during the autumn sexual display, adult birds were much more abundant than in the marginal habitat. During the breeding season, 41% of the nest boxes were occupied in the optimal habitat, compared with 8% in the marginal habitat. The respective figures during the autumn display were 95% and 45%. Autumn nests were built in 83% and 12% of the nest boxes, respectively, and in winter, 35% and 7% of nest boxes, respectively, were used by birds for night-time roosting at night. The autumn display continued from early September to the end of October. For roosting at night in winter (November-March), Tree Sparrows selected nests according to their insulating quality. Most often they roosted in nest boxes containing nests from the breeding season with autumn nests built over them, then, in descending order of frequency, in nest boxes with autumn nests built in empty boxes, in boxes with breeding nests, and in completely empty boxes. Among birds roosting at night and captured on the first survey in winter, 86% were represented by pairs that had built those nests during the autumn display. Young birds that did not build autumn nests typically roosted at night in tree crowns. This implies that the construction of autumn nests is primarily a consequence of the autumn sexual display, and secondarily may be an adaptation for winter survival. The winter survival rate was significantly higher in juvenile Tree Sparrows that were found in nest boxes on winter nights than in those that were not.

Do Otters and Mink Compete for Access to Foraging Sites? a Winter Case Study in the Mazurian Lakeland, Poland

The distribution of otter and American mink tracks in the Mazurian Lakeland during winter, characterised by low temperatures and thick ice cover, was used to analyse competition between the two species for access to the limited area of foraging sites. The study was carried out in February and March, 2006 and comprised 12 lakes and sections of three rivers and two canals. Tracking was conducted along a total of 98.25 km of the shoreline, which was divided into 393 study sections, 250-m-long each. Otter tracks were recorded at all the lakes and canals under study and at two rivers. Mink tracks were recorded along all the watercourses and on eleven lakes. The otter was recorded in 25.9% of the sections, whereas American mink in 28.8% of the sections. Co-occurrence of the otter and mink was observed in 8.8% of the sections. In sections with unfrozen stretches (12.3% of all the study sections), the frequency of otter and mink tracks was significantly higher than in totally frozen sections. Co-occurrence of the otter and mink was found in 28.3% of the sections with access to open water. In unfrozen sections the frequency of co-occurrence of the two species was four times higher than in totally frozen sections. Only 20% of the sections with air holes were not visited by any of the two species. The study showed that during periods of low temperatures, when accessibility to open water and aquatic prey was limited, both species clearly preferred those parts of the water bodies where unfrozen places remained. A high rate of co-occurrence of the two species in such places indicates mutual tolerance between the otter and mink in the sections offering aquatic food resources.

Post-breeding courtship: public information about breeding habitat quality?

AbstractAnimals can estimate breeding habitat quality by monitoring social information provided by the behaviours of others. While it is accepted that the value of public information erodes with distance from the source of information, the spatial and temporal ecology of public information acquisition and use is not well understood. Published accounts of the acquisition of public information for breeding habitat selection show a study bias towards the period corresponding to the breeding season. Here, we explored the idea that post-breeding courtship is a reliable source of performance social information about breeding habitat quality that can be used by nest-site prospectors. We revealed that post-breeding courtship can be used as performance social information for breeding habitat selection in a sedentary, cavity-nesting bird species, the Eurasian Tree Sparrow Passer montanus. First, the occurrence of the autumn nest at a nest box was positively associated with the nest box’s breeding performance in both the preceding and subsequent breeding seasons. Second, nest boxes with owners that showed higher post-breeding courtship activities attracted more prospectors. Namely, more prospectors visited nest boxes momentarily occupied by both owners and containing complete autumn nests at the end of autumn compared to nest boxes momentarily occupied by single owners and containing incomplete autumn nests. We suggest that post-breeding courtship represents performance social information about breeding habitat quality that is accessible to more potential observers than performance social information available during the breeding period is. Also, post-breeding courtship can be even more reliable performance social information than that available during the breeding period because it integrates information provided by informed individuals on the nest site’s breeding performance and post-breeding attractiveness (i.e. use).ZusammenfassungBalzen nach der Brut: allgemeine Information über die Qualität des Bruthabitats? Tiere können mit Hilfe sozialer Information, die durch das Verhalten anderer Tiere bereitgestellt wird, die Qualität eines Bruthabitats abschätzen. Während gemeinhin anerkannt ist, dass der Nutzen allgemeiner Information mit der Distanz zur Informationsquelle abnimmt, ist die räumliche und zeitliche Ökologie der Beschaffung und des Nutzens allgemeiner Information nur schlecht verstanden. Viele der publizierten Studien über die Beschaffung allgemeiner Information für die Wahl eines Bruthabitats konzentrieren sich auf die Brutsaison. Hier haben wir die Idee untersucht, dass Balzen nach der Brut eine zuverlässige Quelle sozialer Information über die Qualität des Bruthabitats darstellt und von Tieren, die auf der Suche nach Nistplätzen sind, genutzt werden kann. Wir zeigen, dass Balzen nach der Brut bei einem höhlenbrütenden Standvogel, dem Feldsperling Passer montanus, in der Tat als soziale Information für die Wahl eines Bruthabitats genutzt werden kann. Erstens fanden sich Herbstnester besonders in Nistkästen, wo in sowohl der vorhergehenden als auch der folgenden Brutsaison ein hoher Bruterfolg erzielt wurde. Zweitens zogen Nistkästen, deren Bewohner nach der Brut stärker balzten, mehr nach einem Nistplatz suchende Tiere an. Und zwar besuchten mehr solcher Tiere Nistkästen, die am Ende des Herbstes vorübergehend von beiden Besitzern besetzt waren und vollständige Herbstnester beherbergten, im Vergleich zu Nistkästen, die vorübergehend von nur einem Besitzer besetzt waren und unvollständige Herbstnester beherbergten. Wir stellen die Hypothese auf, dass Balzen nach der Brut soziale Information über die Qualität eines Bruthabitats bereitstellt, die mehr potenziellen Beobachtern zugänglich ist als während der Brutsaison verfügbare soziale Information. Balzen nach der Brut könnte sogar verlässlicher sein als soziale Information zur Brutzeit, weil sie Information über die Brutleistung des Nistplatzes und die Attraktivität nach dem Brüten (d.h. Benutzung) integriert, die von informierten Individuen bereitgestellt wird.

Ranking landscape development scenarios affecting natterjack toad (Bufo calamita) population dynamics in Central Poland

When data are limited it is difficult for conservation managers to assess alternative management scenarios and make decisions. The natterjack toad (Bufo calamita) is declining at the edges of its distribution range in Europe and little is known about its current distribution and abundance in Poland. Although different landscape management plans for central Poland exist, it is unclear to what extent they impact this species. Based on these plans, we investigated how four alternative landscape development scenarios would affect the total carrying capacity and population dynamics of the natterjack toad. To facilitate decision-making, we first ranked the scenarios according to their total carrying capacity. We used the software RAMAS GIS to determine the size and location of habitat patches in the landscape. The estimated carrying capacities were very similar for each scenario, and clear ranking was not possible. Only the reforestation scenario showed a marked loss in carrying capacity. We therefore simulated metapopulation dynamics with RAMAS taking into account dynamical processes such as reproduction and dispersal and ranked the scenarios according to the resulting species abundance. In this case, we could clearly rank the development scenarios. We identified road mortality of adults as a key process governing the dynamics and separating the different scenarios. The renaturalisation scenario clearly ranked highest due to its decreased road mortality. Taken together our results suggest that road infrastructure development might be much more important for natterjack toad conservation than changes in the amount of habitat in the semi-natural river valley. We gained these insights by considering both the resulting metapopulation structure and dynamics in the form of a PVA. We conclude that the consideration of dynamic processes in amphibian conservation management may be indispensable for ranking management scenarios.

Small mammals of Kampinos National Park and its protection zone, as revealed by analyses of the diet of tawny owls Strix aluco Linnaeus, 1758

Analyses of tawny owl pellets were used to determine the species composition and distribution of small mammals in Kampinos National Park and its protection zone (central Poland). The total material collected from 58 localities contained the remains of 11,235 vertebrates (including 8,335 mammals). The study revealed 29 species of small mammals of the following orders: Soricomorpha – 4, Chiroptera – 9, Rodentia – 14, Lagomorpha – 1 and Carnivora – 1. These included two bat species of special interest (Myotis myotis and Barbastella barbastellus) listed in the 2nd Annex to the Habitats Directive of the European Union. Muscardinus avellanarius, a rodent typical of broad- leaved woodland, appeared to be relatively common and abundant in suitable habitats. Species inhabiting wet habitats, Microtus oeconomus and Neomys fodiens, were found in many localities, whereas Arvicola amphibius was rarer and less abundant. Some important refuges of small mammals were found, mostly in strictly protected areas. Although the studies conducted to date in this area likely reveal a complete list of small species of Soricomorpha and Rodentia, it is possible that 3-5 species of Chiroptera and 2 small species of Carnivora may remain to be identified.

Dam reservoir affects diet of otters inhabiting mountain river in SE Poland

Abstract. The diet of otters was studied by the means of spraint analysis in the Bieszczady Mountains, in southeastern Poland. The study area extended over 25 km long stretch of the River San, about 1 km above Solina dam reservoir. Spraints were collected on seven 2 km long sections in 1993, and on three sections in 2010. In both study periods, otter spraints were collected in August, when the weather conditions were similar. The study revealed high contribution of mountain fish species such as Phoxinus phoxinus, Cottus spp., and Barbatula barbatula in otter diet. Diet composition along the River San showed little variation in 1993, except from the section closest to dam reservoir where it was characterised by the highest frequency of occurrence of perch Perca fluviatilis, cyprinids and amphibians. The share of perch in otter diet decreased, while that of noble crayfish Astacus astacus increased with the distance from Solina reservoir. Changes in otter diet between 1993–2010 were characterized by an increase of the consumption of perch and cyprinids on the one hand, and a decrease of the consumption of crayfish, on the other. Both spatial and temporal changes in otter diet reflected the effect of Solina reservoir on the river community and the availability of prey to otters. The results indicate the ongoing changes in fish community influenced by the construction of Solina reservoir.

Population Viability Modelling and Potential Threats to the Beaver in the Vistula River Valley, Poland

Distribution data on beaver populations thriving in central Poland are common. We modelled beaver population viability to assess the current status and threats to the beaver in the 135-km-long section of the Vistula valley. We simulated different densities of expanding beaver populations and evaluated the three most significant scenarios of potential developments in the valley with the LARCH habitat model. The model output indicated higher vulnerability of low density populations to the same environmental changes. At present, suitable habitats sustain a large minimum viable population as part of one sustainable network. Hypothetical construction of two dams and removal of riparian forests within dykes would lead toa 25% reduction in population size. In contrast, river renaturalisation would increase beaver numbers by 42%. Based on the population trends we conclude that scenario analysis is beneficial in helping to evaluate future management decisions.