Staffan Ulfstrand

Life cycles of benthic insects in Lapland streams (Ephemeroptera, Plecoptera, Trichoptera, Diptera Simuliidae)

A large material of larvae and nymphs of Ephemeroptera, Plecoptera, Trichoptera and Diptera Simuliidae from lotic biotopes in Lapland streams was used for an analysis of life cycle patterns. Flight-periods were determined from collection of winged insects. Although each species had its own distinctive life cycle, certain patterns prevailed and could be classified in several phenological types. The study area was situated on the border between the high boreal and subalpine zones and had an accordingly severe climate with a long period of ice-cover. However, life cycle patterns were not consistently different from those of the same or related species in regions with a milder climate. The life cycles of some species varied from place to place. Some such differences are probably explicable in terms of local temperature differences. The life cycles of some species varied from year to year. Within the same species, some individuals took one year, others two years before reaching emergence.

Composition and Diversity of Benthic Species Collectives Colonizing Implanted Substrates in a South Swedish Stream

Trays with stones were implanted in a south Swedish stream. They rapidly became covered by large quantities of dcbris and detritus. The composition and diversity of the colonizing species collectives were examined after 2, 4, 8, 15 and 32 days. The changing substrate conditions were accompanied by a successive exchange of species demonstrating their capability of active habitat selection. The species diversity first rose but apparently approached an asymptotic level at the end of the experiment. Species richness was the major factor affecting the diversity, while the evenness component played a minor role, at least in more comprehensive samples.

Hybridization as an Agent of Competition between Two Bird Allospecies: Ficedula Albicollis and F. Hypoleuca on the Island of Gotland in the Baltic

Two closely related flycatcher species, Ficedula hypoleuca Pall. and F. albicollis Temm., have largely allopatric distribution ranges in Europe. However, they are sympatric on two islands in the Baltic, where, in contrast to the rest of NW Europe, F. albicollis is much more abundant than F. hypoleuca. Having found a considerable rate of hybridization we suggest that this may prevent F. hypoleuca from building up a large and viable population and thereby to outcompete F. albicollis from its only bastion in NW Europe, i.e. the Baltic islands, where it is probably a relict from a period with circumstances more favourable than at present. Should F. albicollis evolve the faculty of species discrimination, so that hybridization would no longer take place, this would mean the end of its population on the Baltic islands, although the change would enhance individual fitness.

Food resources and breeding frequency of the harlequin duck Histrionicus histrionicus in Iceland.

In four rivers in northern Iceland, benthic standing crop values were lower in 1970 than normal. There are strong indications that the abundance of simuliid larvae, pupae and adults was much below the normal throughout the summer of 1970. Simuliids are the chief food resource of the harlequin duck Histrionicus histrionicus. The breeding frequency of all four populations studied of this species was markedly reduced in 1970.

Age and plumage associated differences of behaviour among blackheaded gulls Larus ridibundus: foraging success, conflict victoriousness and reaction to disturbance

Blackheaded gulls Larus ridibundus L. in juvenile plumage were less efficient foragers than adults and usually were defeated in intraflock conflicts by adults. Juveniles in flocks with no adults present foraged more efficiently than juveniles in flocks with adults. The difference is supposed to be due to interference from the adults. Adult gulls in eclipse plumage foraged as efficiently as adults in nuptial plumage but were socially inferior to them. After disturbance adults landed more quickly but farther from the observer than young birds. On the basis of these observations I discuss (1) advantages and disadvantages of gregariousness for individuals of different social rank, and (2) adaptive background of age and reproductive stage associated plumage differences.

Plumage and Size Variation in Swedish Common Buzzards Buteo buteo L. (Aves, Accipitriformes)

Plumage colouration, using quantitative methods, and size of 320 museum specimens of Buteo buteo from Sweden were measured. The frequency of extremely pale birds was significantly higher in south Sweden than elsewhere. The amount of reddish colour in the plumage was minimal in central Sweden, rising northwards probably because of connexion with more easterly populations, and southwards probably because reddish pigments to a disproportionate degree persist even after an advanced general depigmentation. Size decreases clinally from south to north and a significant negative correlation was established between size and redness. No trace was found of any demarcation line between two distinguishable subpopulations, nor was there any bimodality in the data collected, and therefore nomenclatorial separation of the north Swedish population seems unjustified. Thus, the western limit of Buteo b. vulpinus must be located east of the Baltic. Finally, various factors possibly contributing to the complex pattern of variation in the Swedish population of Buteo buteo are discussed.

Locomotory and dehydrogenase activities of redstarts Phoenicurus phoenicurus L. (Aves) given PCB and DDT

Abstract Caged redstarts trapped during the autumn migration were given PCB and DDT injected into meal-worms. There was a tendency, although not statistically significant, of increased locomotory activity in PCB-treated birds in the early night hours, that is, at the peak of normal migratory activity. Similarly, there was a tendency in both PCB- and DDT-treated birds to altered dehydrogenase activities, suggesting metabolic changes presumably due to the contaminants accumulated during treatment. The organ residue levels found at analysis were comparable to those reported from wild birds in the field. The changes in the dehydrogenase activities were more pronounced for liver and breast muscle of the DDT-treated birds.

Benthic Insect Communities of Streams in Stora Sjöfallet National Park, Swedish Lapland

Benthic animal communities in streams with varying environmental conditions in a national park in northern Swedish Lapland were analysed. Dominant taxa were Ephemeroptera, Plecoptera, Trichoptera and Diptera Simuliidae. Northeasterly or very widely spread species make up the fauna. Intrariverine distribution patterns were found to differ between taxa, and great variations of standing crop values between adjacent sampling sites were the rule. Day-to-day fluctuations of drift rate were unsynchronized between taxa. Some ecological properties of Brachyptera risi (Plec.) are discussed. Some lake shores and streams affected by hydroelectric exploitation appeared virtually devoid of macroscopic animals.