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Urbanization in general and the spread of industrial construction into natural areas can seriously reduce animal populations. The effects often reach beyond the actual point of impact. We monitored wetland bird populations in a nearby Natura 2000 area during the construction of the new Vuosaari Harbour (Helsinki, Finland) in 2002–2011. The harbour was built less than 300 m from a bay, Porvarinlahti, and a railroad bridge was built to cross Porvarinlahti. We compared the wetland bird populations before, during and after construction to evaluate whether the changes observed were linked with the construction work in the nearby harbour area. The numbers of species and territories varied between years and subareas, but we found no clear effects of harbour construction on bird population trends.
Insect cuticle hardens and darkens during the processes of cuticular melanization and sclerotization, and it provides an effective physicochemical barrier against parasites and pathogens. If an invader manages to breach this barrier defense, it is attacked by immune mechanisms in the hemocoel. In this study, we set out to investigate the association between these two lines of defense in the mealworm beetle, Tenebrio molitor. The immune response of freshly emerged beetles was induced with nylon monofilament implants, and later the darkness of their cuticle was assessed. Our study shows that immune challenge has a negative effect on cuticular darkness in T. molitor, which is likely to reflect a trade-off in the allocation of resources between two important components of insect defense system — the protective cuticle and the encapsulation response. The putative trade-off was not affected by the availability of energy resources.
The Siberian jay Perisoreus infaustus has experienced a large decline due to logging in Finland. Populations may also be at risk due to climate warming and interactions with expanding populations of other corvid species. We assessed causes of Siberian jay population changes in southern Norway by conducting field surveys and an online survey addressed to birdwatchers. Field surveys indicated that density of Siberian jays was related to old-growth forest. Density was lower at sites close to the edge of the southeastern distribution margin. Unexpectedly, presence was positively associated with presence of other corvid species. The online survey indicated decreasing populations in logged areas close to the southeastern distribution margin. Respondents reported an increase of other corvid species, but increases were not correlated with decreases of Siberian jays. The field survey and the online survey did not indicate lower population density or population declines at lower-altitude sites (expected if climate change affected the species) when also taking distance from the edge of the southeastern distribution margin into account. In conclusion, there was a decrease in Siberian jay populations at the southeastern distribution margin related to logging, but other corvid species did not affect population trends. Climate change did not appear to be the main factor causing the decline of the Siberian jay, but it cannot be ruled out.
The ring-necked parakeet invaded southern Israel and competes with indigenous cavity-nesting species for nest sites. However, the parakeet can also excavate its own cavities, providing other birds with breeding places, so the final impact on native avifauna is questionable. We studied the effect of the ring-necked parakeet on the indigenous Eurasian hoopoe for 10 years, from 2000 to 2009. The parakeet colonized two palmeries (in 2002 and 2006) with the highest densities of the hoopoe while two remaining palmeries remained unsettled by the parakeet during the study period, and were therefore used as control plots in our study. During the study period, in the unsettled palmeries, the breeding density of the hoopoe did not change while in palmeries colonized by the parakeet, the density of the hoopoe declined significantly. Moreover, the palmery originally hosting the highest density of the hoopoe had the lowest density of this species after the invasion of the parakeet. The results suggest a negative impact of the invasive ring-necked parakeet on the indigenous Eurasian hoopoe, mainly through the aggressive takeover of cavities by parakeets. Expected land-use changes in the region will most probably result in further expansion of the ring-necked parakeet.
After losing their nests or broods due to mowing of grassland, ground-breeding birds may re-nest or disperse from the previous home-range. Breeding corncrakes are frequently affected by mowing of grasslands and often disperse over long distances afterwards. We studied the effects of mowing on departure rates of radio-tagged males from two river floodplain areas in Germany (LOV) and the Netherlands. Birds left from both study areas throughout the breeding season. Daily probabilities that birds survived and remained in the study areas varied between the study areas and within seasons, with lowest values in LOV in June 1998–2000, when mowing was most intensive. When mowing of corncrake habitats was almost completely postponed in LOV 2012–2015, males stayed more than three times as long as previously. Mowing had a strong direct effect on departure rates. The model results show that more than 50% of males died or dispersed within a week after mowing. At the same time, males which were not affected by mowing departed from all study areas, too. Postponed mowing increases the probability of males remaining at the breeding sites thus enabling them to re-nest or initiate second broods. Because dispersing birds can re-nest far away, assessing the situation of the population properly will require a large-scale approach.
The Baltic grey seal (Halichoerus grypus) is a top predator whose numbers have fluctuated during the 2000s in the Finnish sea area. Changes in population size may be due to changes in e.g. population density, food resources and hunting pressure. Here, we examined (1) the trends in grey seal abundance, birth rate of mature females, quality of the main food resource (weight of herring Clupea harengus), and hunting pressure (including the proportions of adults and pups in the catch) in 2003–2015, and (2) the possible effects of birth rate, hunting pressure, and herring weight on abundance index, as well as the possible effects of herring weight and abundance index on birth rate. Results indicated an increasing trend in the grey seal abundance index during the study period. Hunting pressure, especially towards adult seals, explained well the variation in abundance index, suggesting a limiting effect of hunting on population numbers. Herring weight explained well the variation in birth rate but the impact of other factors cannot be ruled out. In recent years, the increasing herring weight and birth rate, and a decreasing hunting pressure and adult hunting mortality probably enabled population growth. A negative relationship between birth rate and abundance index suggested a possibility of some density-dependence of the grey seal population.