All studies of interactions between fleas and hole‐nesting birds so far have been done in nestboxes. This study, which is the first study of flea infestation of nests of hole‐nesters in natural holes, was carried out in the Białowieża National Park (E Poland) and demonstrated that, in contrast to those studies, both prevalence (below 10%) and intensity of infestation nests of Parus palustris and Ficedula flycatchers were very low, an order of magnitude lower than elsewhere. However, in the same forest, flycatchers breeding in nestboxes, and tits in natural holes within the nestbox plot, had significantly higher infestation rates, approaching those found in other studies. These observations indicate that the high flea loads reported for tits and flycatchers may be a product of biased sampling – exclusive collection of data in nestbox areas – rather than reflect their species‐specific characteristics. The data from natural holes undermine the widespread assumption that data on flea loads in nestboxes can be treated as representative, and generalised to areas without nestboxes.

We analyze the frequency of occurrence of small mammals recorded in natural cavities and nest boxes in the Białowieża Forest (eastern Poland) and also describe some parameters of tree cavities. A total of 748 cavities and 60 nest boxes in primeval tree stands and 190 nest boxes in managed tree stands were monitored. Both cavities and nest boxes in primeval stands were occupied by mammals less often than nest boxes in managed stands (0.70%, 0.12%, and 1.26%, respectively). The following mammal species were recorded in natural cavities: Eurasian red squirrel (Sciurus vulgaris L., 1758), forest dormouse (Dryomys nitedula (Pallas, 1778)), yellow-necked mouse (Apodemus flavicollis (Melchior, 1834)), and bats (Microchiroptera species). Three mammalian species were recorded in nest boxes: forest dormouse, fat dormouse (Myoxus glis (L., 1766)), and yellow-necked mouse. The attractiveness of the boxes for mammals increases in managed forests, probably because of a shortage of natural cavities. We suggest that the role of rodents in the breeding ecology of cavity-nesters is underestimated, since studies on natural cavities are rather rare and the species identities of nest predators are most likely poorly recognized. To understand the breeding ecology of birds, ornithologists should study the population dynamics of mammals and the manner in which they use tree cavities and nest boxes.Résumé : Nous analysons la fréquence des petits mammifères retrouvés dans des cavités naturelles et des boîtes de nidification dans la forêt de Białowieźa (Pologne orientale) et nous décrivons certaines des caractéristiques des cavités dans les arbres. Nous avons suivi un total de 748 cavités et 60 boîtes de nidification dans les peuplements forestiers anciens et 190 boîtes de nidification dans les peuplements aménagés. Tant les cavités que les boîtes de nidification des peuplements anciens sont moins fréquemment utilisées par les mammifères que les boîtes de nidification dans les peuplements aménagés (respectivement 0,70 %, 0,12 % et 1,26 %). Les mammifères suivants se retrouvent dans les cavités naturelles : l'écureuil roux (Sciurus vulgaris L., 1758), le lérotin (Dryomys nitedula (Pallas, 1778)), le mulot à collier roux (Apodemus flavicollis (Melchior, 1834)) et des espèces de chauves-souris microchiroptères. Trois espèces de mammifères s'observent dans les boîtes de nidification : le lérotin, le loir gris (Myoxus glis (L., 1766)) et le mulot à collier roux. Dans les forêts aménagées, l'attrait des boîtes augmente chez les mammifères probablement à cause de la pénurie de cavités naturelles. Nous croyons que le rôle des rongeurs dans l'écologie de la reproduction des animaux qui nichent dans les cavités est sous-estimé, car il y a peu d'études sur les cavités naturelles et l'identité des prédateurs des nids est vraisemblablement mal connue. Afin de comprendre l'écologie de la reproduction des oiseaux, les ornithologues devraient étudier la dynamique des mammifères et leur façon d'utiliser les cavités des arbres et les boîtes de nidification....

Biodiversity‐rich grasslands have been severely impacted by agricultural intensification. Although agri‐environment schemes (AES) have been launched partly to combat grassland biodiversity erosion, they could neither halt nor revert it, and this calls for alternative solutions. We carried out controlled experiments on the effects of three mowing regimes on the arthropod biodiversity of extensively managed meadows, testing whether alternative mowing regimes can improve AES effectiveness: (i) mowing according to the Swiss AES prescriptions, i.e. first cut not before 15 June (control meadows); (ii) first cut not before 15 July (delayed mowing); (iii) refuge left uncut on 10–20% of the meadow area, otherwise first cut not before 15 June. Leaf‐ and planthoppers (Auchenorrhyncha) and spiders (Araneae) were sampled before and after mowing during 3 years, which enabled testing for immediate (within season) and carry‐over (1 year to the next) effects. Regarding immediate effects, Auchenorrhyncha and Araneae increased in abundance under the delayed mowing regime, with densities 3.5 and 1.8 times higher, respectively, than in control meadows. Furthermore, a positive carry‐over effect was detected for Araneae density under the delayed mowing regime. The refuge mowing regime had no effect on abundance. Finally, no statistically significant changes were detected for species richness and diversity (Shannon index) after 2 years of manipulations. We conclude that delaying the first cut in extensively managed meadows promotes these two taxa. It could be easily implemented by slight adjustments of the extant grassland AES.

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The question whether total population energy use is invariant to species body size (the energy equivalence hypothesis) is central to metabolic ecology and continues to be controversial. While recent comparative field work and meta-analyses pointed to systematic deviations of the underlying allometric scaling laws from predictions of metabolic theory none of these studies included the variability of metabolic scaling in ecological time. Here we used extensive data on the invertebrate soil fauna of Kampinos National Park (Poland) obtained from six consecutive quantitative sampling seasons to show that phylogenetically corrected species density—body weight and population energy use—body weight relationships across all soil fauna species and within trophic groups and body weight classes were highly variable in time. On average, population energy use tended to increase with species body weight in decomposers and phytophages, but not in predators. Despite these trends, our data do not exclude the possibility that energy equivalence marks the central tendency of energy use in the edaphon. Our results highlight the need for long-term studies on energy use to unequivocally assess predictions of metabolic theory.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-015-3317-3) contains supplementary material, which is available to authorized users.

The impact of disturbance on animal and plant assemblages has been described mainly in terms of aggregate community properties like species richness, abundance, or productivity. However, the question how disturbance acts on species interactions, particularly on patterns of co-occurrence, has received much less attention. Here we use a large pitfall trap sample of spiders from two complexes of lake islands in Northern Poland to show how disturbance by tourist visits affects species richness, composition and co-occurrence. On the pristine and protected islands of Lake Wigry, species co-occurrence was significantly segregated. Further, island species richness and abundances could be predicted from environmental correlates, particularly from island area, soil fertility and humidity. In turn, on the lake islands that are frequently visited by tourists, species co-occurrences were random and environmental correlates other than island area failed to predict species richness and abundances. However, species composition, α−, β-, and γ-diversities, as well as average local spider abundances did not significantly differ between both island complexes. Our results show that disturbance disassembles the structure of spider communities prior to visible richness and abundance effects. This result has implications for biological conservation. The detection of community disassembly might be an early sign for factors that act negatively on ecosystem functioning. Abbreviations: NBM NMDS SAR ReceivedRevised Accepted

Competition theory predicts that species of similar ecological niches are less likely to coexist than species with different niches, a process called species assortment. In contrast, the concept of habitat filtering implies that species with similar ecological requirements should co-occur more often than expected by chance.Here we use environmental and ecological data to assess patterns of co-occurrence of regional communities of spiders distributed across two assemblies of lake islands in northern Poland. We found aggregated and random co-occurrences of species of the same genus and a significant tendency of species segregation across genera. We also found that species of the same genus react similarly to important environmental variables. A comparison of ecological traits of species of the local communities with those expected from a random sample from the regional Polish species pool corroborated partly the habitat filtering hypothesis. On the other hand, we did not find evidence for species assortment.Our results also imply that at least some observed species co-occurrences result from niche differentiation.

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