Breeding success of a Lesser Spotted Woodpecker Dendrocopos minor population

We made intensive observations of 50 pairs of Lesser Spotted Woodpecker Dendrocopos minor in southern Sweden from 1989 to 1992. Between 7% and 22% of the pairs each year defended a territory but laid no eggs. Overall, 76% of the pairs laying eggs raised fledglings, but this proportion was only 33% in 1991 when the weather was cold and wet. The mean clutch size (5.9) and brood size (4.5) in successful nests did not vary significantly between years. Incubation time was 1 day longer in 1991 (11–12 days) than in 1990 and 1992 (10–11 days). Number of young fledged per nesting attempt (3.5) and per pair (2.7) in the population also varied significantly between years. The initiation of egg laying varied between years but coincided each year remarkably well with the date when oak came into leaf. Breeding success is discussed, and comparisons are made with other hole-nesting species.     

Heat tolerance of strawberry tarsonemid mite Phytonemus pallidus

The heat tolerance of the strawberry tarsonemid mite Phytonemus pallidus ssp. fragariae was studied in northern Sweden by treating adult mites in hot water at temperatures 44°C, 46°C and 48°C. During the summer, the shortest exposure times required to kill all adult mites at these temperatures were 6, 2.5 and 1.25 min, respectively. It is concluded that hot‐water treatment of strawberry runners for 6.5 min at 46°C would suffice to kill all tarsonemid mites on infested runners. This exposure time includes the time needed to raise the temperature of the plant material to that of the water bath. In the autumn, from the middle of September and later, the mites became successively much more heat tolerant as they prepared for hibernation. It is expected that longer exposure periods are needed to kill mites on frigoplants.     

Stimulation of microbial extracellular enzyme activities by elevated CO2 depends on soil aggregate size

Increased belowground carbon (C) transfer by plant roots at elevated CO₂ may change properties of the microbial community in the rhizosphere. Previous investigations that focused on total soil organic C or total microbial C showed contrasting results: small increase, small decrease or no changes. We evaluated the effect of 5 years of elevated CO₂ (550 ppm) on four extracellular enzymes: β‐glucosidase, chitinase, phosphatase, and sulfatase. We expected microorganisms to be differently localized in aggregates of various sizes and, therefore analyzed microbial biomass (C_mic by SIR) and enzyme activities in three aggregate‐size classes: large macro‐ (> 2 mm), small macro‐ (0.25–2 mm), and microaggregates (< 0.25 mm). To estimate the potential enzyme production, we activated microorganisms by substrate (glucose and nutrients) amendment. Although C_total and C_mic as well as the activities of β‐glucosidase, phosphatase, and sulfatase were unaffected in bulk soil and in aggregate‐size classes by elevated CO₂, significant changes were observed in potential enzyme production after substrate amendment. After adding glucose, enzyme activities under elevated CO₂ were 1.2–1.9‐fold higher than under ambient CO₂. This indicates the increased activity of microorganisms, which leads to accelerated C turnover in soil under elevated CO₂. Significantly higher chitinase activity in bulk soil and in large macroaggregates under elevated CO₂ revealed an increased contribution of fungi to turnover processes. At the same time, less chitinase activity in microaggregates underlined microaggregate stability and the difficulties for fungal hyphae penetrating them. We conclude that quantitative and qualitative changes of C input by plants into the soil at elevated CO₂ affect microbial community functioning, but not its total content. Future studies should therefore focus more on the changes of functions and activities, but less on the pools.     

The Appearance and Development of Photosynthetic Activity in Etiolated Barley Leaves and Isolated Etio-chloroplasts

The appearance and development of the oxygen exchanging capacity of greening barley leaves were measured using a manometric technique and an oxygen race electrode. An oxygen evolution could first be detected after one hour of greening. During the first hour of greening a light-dependent oxygen uptake was observed. The oxygen evolving capacity, calculated on a chlorophyll weight basis, showed a fast rise in activity during the first hours of greening. A maximal activity was reached after 5 to 10 hours of greening; the oxygen evolution then declined. Using oxygen electrodes different aspects of the electron transport in etio-chloroplasts prepared from the greening barley leaves were also investigated. The activity in photosystem I and II, as well as the cooperation between the two photosystems, were studied by measuring the oxygen exchange from the etio-chloroplasts in the absence and presence of added oxidants and reductants. An activity in photosystem I could be detected already after 5 minutes of greening. The activity of photosystem I, when calculated on a chlorophyll basis, had the same appearance as the oxygen evolution from the intact plant material. An activity in photosystem II and a cooperation between the two photosystems were first detected after 3 hours of greening. After about 15 hours of greening a cooperation corresponding to that from chloroplasts prepared from normal green leaves was observed.     

Characteristics and utilization of old Black Woodpecker Dryocopus martius holes by hole-nesting species

Old nest holes made by the Black Woodpecker Dryocopus martius were examined in two study areas in Sweden. We found a large variation in nest hole characteristics and that the height in the tree and depth of the hole were important factors in the choice of nest hole by secondary hole nesters. A large proportion of old nest holes remained unoccupied. Many holes were probably of poor quality due to shallow depth, low height or narrow entrance. Nest holes in the vicinity of farmland (<200 m from the field-forest edge) were more often occupied than nest holes deeper into the forest. This was because Jackdaws Corvus monedula , the numerically dominant species, only used nest holes near farmland. Jackdaws usually used the best nest holes, while other subordinate species had to use inferior holes near fields or nest holes in areas with less competition, deeper in the forest. Besides birds, some mammals and bees were found using old Black Woodpecker holes.     

A Note on Opportunism and Parsimony in Data Collection

ABSTRACT Out of precaution, opportunism, and a general tendency towards thoroughness, researchers studying wildlife often collect multiple, sometimes highly correlated measurements or samples. Although such redundancy has its benefits in terms of quality control, increased resolution, and unforeseen future utility, it also comes at a cost if animal welfare (e.g., duration of handling) or time and resource limitation are a concern. Using principle components analysis and bootstrapping, we analyzed sets of morphometric measurements collected on 171 brown bears in Sweden during a long-term monitoring study (1984–2006). We show that of 11 measurements, 7 were so similar in terms of their predictive power for an overall size index that each individual measurement provided little additional information. We argue that when multiple research objectives or data collection goals compete for a limited amount of time or resources, it is advisable to critically evaluate the amount of additional information contributed by extra measurements. We recommend that wildlife researchers look critically at the data they collect not just in terms of quality but also in terms of need.