Rintamäki, P. T., Höglund, J., Alatalo, R. V. & Lundberg, A. 2001: Correlates of male mating success on black grouse (Tetrao tetrix L.) leks. — Ann. Zool. Fennici 38: 99–109.
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Moreno, J., Potti, J., Yorio, P. & García-Borboroglu, P. 2001: Sex differences in cell-mediated immunity in the Magellanic penguin Spheniscus magellanicus. — Ann. Zool. Fennici 38: 111–116.
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Rantala, M. J., Hovi, M., Korkeamäki, E. & Suhonen, J. 2001: No trade-off between the size and timing of emergence in the damselfly, Calopteryx virgo L. — Ann. Zool. Fennici 38: 117–122.
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Nummi, P. & Väänänen, V.-M. 2001: High overlap in diets of sympatric dabbling ducks — an effect of food abundance? — Ann. Zool. Fennici 38: 123–130.
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Tryjanowski, P. 2001: Proximity of raven (Corvus corax) nest modifies breeding bird community in an intensively used farmland. — Ann. Zool. Fennici 38: 131–138.
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Pérez-Tris, J., de la Puente, J., Pinilla, J. & Bermejo, A. 2001: Body moult and autumn migration in the barn swallow Hirundo rustica: is there a cost of moulting late? — Ann. Zool. Fennici 38: 139–148.
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Smallwood, K. S. & Smith, T. R. 2001: Study design and interpretation of shrew (Sorex) density estimates. — Ann. Zool. Fennici 38: 149–161.
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Kotta, J. & Orav, H. 2001: Role of benthic macroalgae in regulating macrozoobenthic assemblages in the Väinameri (north-eastern Baltic Sea). — Ann. Zool. Fennici 38: 163–171.
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Kojola, I. & Laitala, H.-M. 2001: Body size variation of brown bear in Finland. — Ann. Zool. Fennici 38: 173–178.
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Pöysä, H., Sjöberg, K., Elmberg, J. & Nummi, P. 2001: Pair formation among experimentally introduced mallards Anas platyrhynchos reflects habitat quality. — Ann. Zool. Fennici 38: 179–184.
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Rintamäki, P. T., Höglund, J., Alatalo, R. V. & Lundberg, A. 2001: Correlates of male mating success on black grouse (Tetrao tetrix L.) leks. — Ann. Zool. Fennici 38: 99–109.
Sexual selection in black grouse was studied through multivariate analyses of possible correlates of mating success using data from an eight year study of 10 different leks. Body size was weakly correlated with mating status (0 or >= 1 mating) and tail length was significantly correlated with mating success (total number of copulations) even after controlling for the effects of age and body size. Among several behavioural variables, having a high attendance, being more active and having the tail lyre-feathers erected more often were significantly related to high mating success also when age and the other factors were controlled for. In addition, there were strong relationship between a combined measure of territorial centrality and territory size and their interaction such that males that held relatively large central territories had higher mating success. Males that spent more time rookooing (display) had lower mating success. This last somewhat counter-intuitive result could be explained by a significant interaction between rookoo and centrality; central and successful males were engaged in more interactions with neighbours, and therefore were not allowed to display as often as peripheral unsuccessful males. Display activity indeed turned out to be a significant factor of mating success when we controlled for territory position. All of the significant variables are likely to reflect male motivation and/or competence. The results thus indicate that successful males are signified by being healthy, active and capable to defend relatively large central territories on the leks. We conclude that sexual selection in black grouse is most likely mediated both by male-male competition and female preference.
Moreno, J., Potti, J., Yorio, P. & García-Borboroglu, P. 2001: Sex differences in cell-mediated immunity in the Magellanic penguin Spheniscus magellanicus. — Ann. Zool. Fennici 38: 111–116.
Males in domestic and laboratory populations usually display a lower immunocompetence than females due to differential action of steroid hormones, but information for natural populations is scant. Here we show that male Magellanic penguins Spheniscus magellanicus had a significantly lower cell-mediated immunity at hatching of their chicks than females. This was assayed through the phytohemagglutinin injection assay, a standard method of measuring T-cell-dependent immunocompetence in birds. Breeding phenology affected condition at laying and cell-mediated immunity at hatching for males, with higher values for late-breeding males. In females, condition at laying declined with breeding date, with no link with immunocompetence at hatching. Early breeding males may incur date-dependent costs in terms of condition and subsequent immunocompetence.
Rantala, M. J., Hovi, M., Korkeamäki, E. & Suhonen, J. 2001: No trade-off between the size and timing of emergence in the damselfly, Calopteryx virgo L. — Ann. Zool. Fennici 38: 117–122.
Many species of insects have been reported to show seasonally declining size at emergence. This has been explained as an adaptive response to time constraint between size and age at maturity (emergence). We studied seasonal variation in the size of damselfly Calopteryx virgo L. in six different creeks in central Finland. The length of hind wings was measured for 942 males and 285 females covering the flying period from mid June to mid August. The length of the hind wings of damselflies did not decrease towards the end of flying period in any river or either sex. In light of this study, seasonal reduction of body size is not a general phenomenon among odonates contrary to common understanding.
Nummi, P. & Väänänen, V.-M. 2001: High overlap in diets of sympatric dabbling ducks — an effect of food abundance? — Ann. Zool. Fennici 38: 123–130.
We studied diet patterns of six sympatric dabbling ducks (Anas sp.) in wetlands with abundant invertebrates. In contrast to some earlier studies, we found no correlation between the lamellar density of different ducks and the mean length of prey in their diet. The size distributions of prey in the diet of different ducks varied, however, although in most cases the differences were not very large. Compared with earlier studies, the prey size distributions in the diet of the ducks differed quite little from that in the environment. There was not much segregation of food use along the vertical foraging dimensions, although teal Anas crecca and wigeon Anas penelope used invertebrates above the water surface. We propose that the high level of diet overlap was promoted by abundant food resources, which are quite typical for habitats where many species of dabbling ducks coexist.
Tryjanowski, P. 2001: Proximity of raven (Corvus corax) nest modifies breeding bird community in an intensively used farmland. — Ann. Zool. Fennici 38: 131–138.
In this paper I tested the hypothesis that areas around nests of raven Corvus corax built on electricity pylons in an intensively used farmland are avoided by small birds as their nest sites. Birds were counted along 13 transects (length 1000 m, width 200 m) starting from pylons with raven nests, as well as 13 control transect lines which started from pylons without any nests. These two types of transects did not differ with respect to the number of recorded bird species. However, the proximity of raven nests positively affected the total density of bird species, including skylark Alauda arvensis, the most abundant bird species. Neither the presence of raven nests nor control pylons influenced the number of breeding bird species along 100-m sections of the transect. Total density of breeding birds decreased with the increasing distance from raven nests, whereas it increased with the distance from control pylons. Contrary to expectations, these results indicate the positive impact of raven presence on breeding bird community in an open farmland. I suggest that breeding of birds near raven nests is an antipredator adaptation against nest-robbing by other predators.
Pérez-Tris, J., de la Puente, J., Pinilla, J. & Bermejo, A. 2001: Body moult and autumn migration in the barn swallow Hirundo rustica: is there a cost of moulting late? — Ann. Zool. Fennici 38: 139–148.
The timing of moult in birds is thought to be constrained by physiological trade-offs. We studied barn swallows in central Spain to assess whether (a) body moult tends to be temporally separated from migration in adult and first-year birds, (b) it is related to an impaired fattening, and (c) its overlap with migration may involve adverse energetic effects. First-year swallows tended to moult early in the post-breeding period: the proportion of first-year birds in active moult was highest in July, and it decreased progressively until September. On the other hand, adult swallows tended to avoid moulting both in the post-breeding (July) and the migratory period (September), concentrating their moulting period in August. In all periods, swallows in active moult stored less fat than non-moulting ones, suggesting a faster depletion of energy resources by moulting birds. Swallows in active moult showed a better body condition — measured as body mass relative to body size and fat content — than non-moulting ones before migration (coinciding with the periods of highest frequency of moulting individuals), but the opposite was found during autumn migration. Our results support the existence of a physiological trade-off between body moult and migration, which could have fitness consequences; thus, if these activities overlap it would impair migration performance of swallows.
Smallwood, K. S. & Smith, T. R. 2001: Study design and interpretation of shrew (Sorex) density estimates. — Ann. Zool. Fennici 38: 149–161.
Population density estimates are a significant aspect of ecological theory. Of the approximately 6000 shrew literature citations, we located none that compared shrew density estimates and explained their variation. We compared 476 usable estimates of shrew density reported in 27 publications for 10 of the 70 species in the genus Sorex. Several factors explained the variation in density, including study area size, year of study, site selection, sampling method, trap type, reported vegetation details, elevation, and body mass. Unlike many larger mammals, shrew numbers were often estimated at study areas too small to encompass "populations". The 59 study areas ranged in size from 0.041 to 9.975 ha, numerical estimates ranged from 0 to 249 shrews, and density estimates ranged from 0 to 17 667 shrews km–2. The average numerical estimate was only 14 shrews and the highest densities were recorded at the smallest study areas. The numerical estimates and study area sizes of shrews were disproportionately small compared to estimates of highly carnivorous species of Carnivora. Our results can provide guidance for setting and designing future studies of shrew numerical patterns that could contribute substantially to knowledge of shrew biology.
Kotta, J. & Orav, H. 2001: Role of benthic macroalgae in regulating macrozoobenthic assemblages in the Väinameri (north-eastern Baltic Sea). — Ann. Zool. Fennici 38: 163–171.
The relationships between the abundance and biomass structure of invertebrate assemblages and environmental variables were sought by using multivariate statistics. Sediment type explained the biggest part of the variation in invertebrate assemblages in the deeper areas and dominant macroalgae in the shallower areas. Additionally, the loose-lying macroalgae, Furcellaria lumbricalis, contributed to the increase in macrozoobenthos densities in the deeper parts of the Väinameri by offering secondary substrate for true hard bottom invertebrates. The infauna below the algal mat was poor when compared to the sediments in unvegetated areas. On the other hand, the introduced polychaete, Marenzelleria viridis, was found only under the mat of F. lumbricalis and the biomass of the polychaete increased with the coverage of F. lumbricalis.
Kojola, I. & Laitala, H.-M. 2001: Body size variation of brown bear in Finland. — Ann. Zool. Fennici 38: 173–178.
Brown bear (Ursus arctos) can be predicted to have larger autumn body mass in the north than south because the duration of winter dormancy lengthens towards the north. We examined variation of body size among hunter-killed female and male brown bears within a latitudal range of 60 and 68deg.N in Finland. The body size of males (mass, contour length) decreased towards the north while our data did not indicate such a trend in females. Our results do not coincide with Bergmann's rule suggesting increasing body size with decreasing ambient temperature, probably owing to energy-saving winter dormancy during which brown bear is not overtly exposed to weather conditions. Secondly, possible differences in the quality of green forage might not largely influence the nutrition of an omnivorous mammal.
Pöysä, H., Sjöberg, K., Elmberg, J. & Nummi, P. 2001: Pair formation among experimentally introduced mallards Anas platyrhynchos reflects habitat quality. — Ann. Zool. Fennici 38: 179–184.
Using data from two independent field experiments, we address whether pair formation in introduced mallards Anas platyrhynchos is associated with habitat quality, specifically food limitation at the brood stage. Based on the concentration of total phosphorous in the water, the study lakes were divided into two groups, `poor' and `rich'. In one of the experiments we used mallard ducklings imprinted on humans to study mass change of ducklings in poor and rich lakes, respectively. It turned out that ducklings foraging on poor lakes gained less mass than ducklings foraging on rich lakes, the division of lakes thus reflecting habitat quality at the brood stage. Introduced mallards formed heterosexual pairs on lakes that were, in a relative sense, high-quality brood habitats, whereas they did not on lakes of low-quality brood habitat. Pair formation thus seemed to reflect the suitability of habitat for breeding.