Research interests

The unprecedented rate of global biodiversity loss, mainly due to human over-exploitation of natural resources, calls for the attention of all sectors of the society particularly biologists. My major research interests are influenced by the loss of biodiversity, also in the developing world, and they are focused on the interface between species richness – community ecology – population ecology. Yet, all mechanisms acting on these levels are not fully understood and therefore my studies combine applied as well as basic research.

Projects  

1. Determinants of species richness and nestedness among birds and plants in arctic and sub-arctic areas.

Much interest has been devoted to find a scale independent mechanism for species richness because the N-S gradient extends across so many taxa that a general explanation is expected. At high latitudes, the high rate of global warming is a rapidly increasing risk of changes in important ecological processes as well as global extinction of members of the biota. Many recent studies, using species’ range maps, remotely sensed vegetation and climate variables, show correlations between species richness and variables associated with energy, habitat diversity and climate. However, one problem is that some of these indices may not apply to all scales, e.g. greenness does not account for the effect of temperature on photosynthetic rate. Therefore, to corroborate the findings of continental wide studies, studies on smaller scales are required. I use a unique data set from many stations in the Western Arctic to examine factors influencing species richness particularly the relationship between nestedness and species richness.  

2. The effects of global warming on the bird fauna in the Swedish alpine region.

The rate of global warming is so high in the Swedish mountain areas that there is a great risk of changes in the biotic communities. Yet, however, ongoing changes have not been substantiated by data, which makes realistic projections of the development difficult. Birds are excellent indicators of environmental change, also effects of climate change, and can therefore be used to predict the development over large areas. This project aims to study the effects of climate change that influence the bird communities in Padjelanta, the most species rich area of the World Heritage Area Lapponia in N. Sweden. There, climatic factors limit the distribution and breeding performance of many bird species, which makes it easier to quantify the effects of global warming on reproduction, population dynamics and food supply and predation. During 1971-1995, studies were made of the reproductive performance of fieldfares, merlins, hooded crows as well as of the population dynamics of the passerine communities in the birch forest and on the tundra. Thus, together old and new data will cover a period of some 35 years, which is long enough to measure climatic effects in biological systems.  

3. Ecosystem services by birds.

One part of the project studies ornithophilous pollination systems among important agro-forestry plants in Ethiopia. The birds in focus are the most important bird pollinators, nectar-feeding sunbirds, which are unrivalled as flower specialists among birds in Africa. They transfer pollen over a wide area, up to several km, and deposit more pollen per capita than bees. Particular attention is given to specialised pollination system because if a plant requires a certain pollinator species, that plant species should be grown only in areas where the pollinator species occurs or the pollinator species should be introduced before or simultaneously with the plant. This type of analysis and subsequent treatment are rarely done. Moreover, plants that depend on the services of one or a few animal species are expected to run a higher risk of extinction than other plants because the vulnerabilities of the mutualists are added to those of the plant itself.

The other part of the project studies factors limiting the breeding populations of rodentivorous birds and their prey. There is growing evidence of top-down control in food webs including food webs with rodents. The relaxation of this control may cause trophic cascades resulting in unexpected changes on lower levels of the food web. In areas with unlimited access to breeding sites, raptor populations are regulated by food and vice versa in areas with excess food. A globally, common trait in farmland areas is that habitat fragmentation causes loss of nesting sites and thus reduces the population size of raptors. Many examples indicate that provision of nest sites results in increasing populations of rodentivorous birds in human dominated areas as well as in less disturbed areas. Yet, similar trials have not been done in farming areas in Africa. A likely scenario for African farming areas is that habitat fragmentation has reduced predator populations and thus relaxed the predation pressure so much that rodent population dynamics has changed from stable, dampened fluctuations to cyclic changes in population numbers, similar to those found at higher latitudes. Thus, improved breeding conditions for rodentivorous birds are expected to affect the population dynamics of rodents in African agricultural areas where grass rats can reduce the grain harvest by 50% or more. 

4. Nestedness: Its temporal development and the influence of habitat on nestedness.

Explaining the factors underlying the non-random assembly of biological communities remains a major goal in ecology. Nestedness is one example of non-random distributions that has been shown for a wide variety of taxa. Mechanisms proposed to cause nestedness include predictable extinction sequences, differential colonization, and nested distribution of habitat types and nested habitat quality. Correlative evidence at the assemblage level does not fully reveal the species–specific patterns underpinning the nested pattern, and other non-random community patterns. However, rarely are nestedness and non-nestedness examined concurrently. This study examines the temporal development of nestedness among insular bird communities, in the Dahlak Archipelago, SW Red Sea, as well as the importance of species-habitat associations for nestedness of birds in this area and among birds in the Arctic.  

5. Population ecology of the merlin Falco columbarius: A long-term study of population dynamics, reproductive performance, survival and dispersal.

Selected publications

Temporal dynamics and nestedness of an oceanic island bird fauna. 2006 Global Ecology and Biogeography, 15, 328-339. (E.T. Azeria, A. Carlsson, T. Pärt, CG. Wiklund).

Terrestrial trophic dynamics in the Canadian Arctic. 2003. Can. J. Zool., 81, 827-843.

Food as a mechanism of density dependent regulation of breeding numbers in the merlin Falco columbarius. 2001. Ecology 82, 860-867.

Lemming predators on the Siberian Tundra 1999. Ambio 28:281-286 (C.G. Wiklund, A. Angerbjörn, E. Isakson, N. Kjellén, M. Tannerfeldt).

Mechanisms determining the distribution of microtine predators on the Arctic tundra. 1998. J. Anim. Ecol. 67, 91-98 (C.G. Wiklund, E. Isakson & N. Kjellén)

Body length and wing length provide univariate estimates of overall body size in the merlin. 1996. The Condor 98:581-588.

Determinants of dispersal in breeding merlins Falco columbarius. 1996. Ecology 77:1920-1927.

Breeding lifespan and nest predation determine lifetime production of fledglings by merlin Falco columbarius males. 1996. Proc. R. Soc. Lond. B 263:723-728.

Predation and lifespan: components of variance in LRS among merlin Falco columbarius females. 1995. Ecology 76:1994-1996.

Rovfåglar och lämlar på ryska ishavstundran. 1995. Vår Fågelv. 1:25-27.  (C. G. Wiklund, E. Isaksson & N. Kjellén).

The distribution of breeding merlins Falco columbarius in relation to food and nest sites. 1994. Ornis Svecica 4:113-123. (C. G. Wiklund & B. Larsson)

Natural selection of colony size in a passerine. 1994. J. Anim. Ecol. 63:765-774. (C.G. Wiklund & M. Andersson)

Sexual and Seasonal variation in Territorial behaviour of kestrels Falco tinnunculus. 1992. Anim. Behav. 43:823-830. (C. G. Wiklund & A. Village)

The Snowy Owl - nomads of the Arctic. 1991. (In Swedish). Fåglar i Stockholmstrakten 1:37-41.