Cilla Kullberg

Cecilia Kullberg

Researcher, Docent

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Works at Department of Zoology
Telephone 08-16 47 13
Visiting address Svante Arrhenius väg 18b
Room D550c
Postal address Zoologiska institutionen: Ekologi 106 91 Stockholm

About me

I have a PhD in evolutionary ecology, I am associate professor (docent) in ethology, and have been performing research in both ecology and ethology at the department of Zoology. At present I mainly study effects of climate change on birds, but I am also interested in many aspects of bird migration, and behavioral adaptations to predation risk.   




I am director of studies in Faunistics at the Department of Zoology and coordinator for the Bachelor thesis course in biology, marine biology and molecular biology. I am also coordinator for the courses Traineeship in Biology and the evening course Bird ecology, systematics and behavior.




Long-term effects of climate change on Swedish bird populations

Global warming is affecting the annual cycle of birds with consequences on population trends. Still, there is a need to understand the large variability between species, and the mechanisms underlying current phenological changes to foresee future effects on biodiversity of avian species and their ecosystem services. In this project we investigate the effects of climate change on shifts in wintering areas, breeding time and reproductive success of birds breeding in Sweden, by time-series analysis of ringing data and nest reports (collected 1950 and onwards) in relation to environmental variables such as temperature, rain and a vegetation index. The project is funded by The Bolin Centre for Climate Research; Research Area 8.


I also take part in a project that in detail study the breeding population of willow warbler in the vicinity of Tovetorp Reseach Station, which has been going on since 1979. From 2020 I also take part in David Wheatcroft’s project on song learning and vocalization in birds.



  • Dr Marta Lomas Vega; Post Doc, SU, Dept of Zoology
  • Prof Thord Fransson; Swedish Museum of Natural History
  • Dr David Wheatcroft; SU, Dept of Zoology
  • Prof Sven Jakobsson; SU, Dept of Zoology
  • Dr Johanna Hedlund; University of Exeter; UK



Earlier PhD students

  • Maria Almbro: Flight ability in butterflies; 2009
  • Ian Henshaw: Avian migration -the role of geomagnetic cues; 2009
  • Robert Stach: Migratory routes and stopover behavior in avian migration; 2016



A selection from Stockholm University publication database
  • Thord Fransson (et al.).

    Migratory birds wintering in Africa face the challenge of passing the Sahara desert with little opportunities to forage. During spring migration birds thus arrive in the Mediterranean area after crossing the desert with very low energy reserves. Since early arrival to the breeding grounds often is of importance to maximize reproductive success, finding stopover sites with good refuelling possibilities after the Saharan passage is of utmost importance. Here we report on extensive fuelling in the great reed warbler, Acrocephalus arundinaceus, on the south coast of Crete in spring, the first land that they encounter after crossing the Sahara desert and the Mediterranean Sea in this area. Birds were trapped with mist nets at a river mouth, individually ringed and information about body mass, wing length, muscle score and fat score were recorded. Due to an exceptional high recapture rate at the trapping site (45%), we were able to calculate minimum stopover time and fuel deposition rates in 25 individual great reed warblers during one spring season. The large proportion of trapped great reed warbler compared to other species and the large number of recaptures suggests that great reed warbler actively choose this area for stopover. The relatively long stopover period at the site, the high fuel deposition rate (1 g day-1) and the large body mass increase show that great reed warblers at this site regularly deposit a much larger fuel load than needed for one continued flight stage to the north. It was also shown that birds with lower body mass at first capture had a higher fuel deposition rate than birds with higher body mass. This indicates that individuals are able to adjust their food intake in relation to energy reserves.

  • Ian Henshaw (et al.).
  • Robert Stach (et al.).

    Birds migrating late in the migration season may need to compensate for the late departure by increasing migration speed. To increase migration speed late migrants should depart from stopovers along the route with larger fuel loads than early migrants. Both higher migration speeds and increasing fuel loads with the progress of the season have been reported in the literature. Here we test if Garden Warblers (Sylvia borin) show different fuelling strategies when captured on migration in the early or late part of autumn migration and given unlimited access to food. We also included a group of birds that were captured early in the season but held under a light regime with shorter day lengths to simulate thirty days advancement in time. We found no difference in maximum body mass between the groups and all groups reached fairly large fuel loads (mean: 39.2 % of lean body mass). Maximum fuel load was also strongly correlated with fuel deposition rate and this may suggest that Garden Warblers migrate at high speed during the entire season, which leaves little room for increasing speed later in the season.

Show all publications by Cecilia Kullberg at Stockholm University

Last updated: May 15, 2020

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