GfÖ 2014 • Hildesheim, September 8th
Can We Use Functional Types to Predict Responses of Birds to Changes in African Savannas? An Individual-Based Modelling Approach CÉDRIC SCHERER, FLORIAN JELTSCH, VOLKER GRIMM & NIELS BLAUM
[email protected]
Animal Functional Type Model: Introduction
2
Shrub Encroachment in Semi-Arid Savannas (e.g. ARCHER et al. 1995, SCHOLES & ARCHER 1997, KRAAIJ & WARD 2006, COETZEE et al. 2008, ARCHER 2010)
land use
climate change vegetation composition fragmentation
habitat suitability
3
Animal Functional Type Model: Concept
Key Questions Which traits make species sensitive for changes in vegetation structure? Which functional types will be lost first due to these changes?
» Approaches:
↪ functional trait classification ↪ spatially-explicit indivudal-based model in NetLogo
Animal Functional Type Model: Concept
The Animal Functional Type (AFT) Model body mass: continuous values in g ⤷ reproduction (REISS 1991) ⤷ mortality rate (CALDER 1983) ⤷ age-related traits (PRINZINGER 1993) ⤷ home range area (OTTAVIANI et al. 2006) ⤷ dispersal abillities (SUTHERLAND et al. 2000)
vegetation use • habitat preference: open grassland vs bush thickets ⤷ home range area (OTTAVIANI et al. 2006) ⤷ diet (DONALDSON & KELK 1970, SEYMOUR & DEAN 2010)
• nest site needs: on trees vs on large shrubs vs ground-breeding (NEWMAN 2002, HOCKEY et al. 2005)
4
5
Animal Functional Type Model: Concept
Model Structure Vegetation layer
1 year
Rainfall
LANDSCAPE
calculation habitat quality
Territory layer
Ageing Dispersal Reproduction Survival
BIRDS
5
Animal Functional Type Model: Concept
Model Structure Vegetation layer
1 year
Rainfall calculation habitat quality
Territory layer
Ageing
LANDSCAPE
habitat preference precipitation
BIRDS
Dispersal
habitat quality
Reproduction
habitat quality
Survival
habitat quality
6
Animal Functional Type Model: Concept
Landscape Scenarios » Artificial landscapes varying in encroachment and clumping intensity
7
Animal Functional Type Model: Temporal dynamics
Exemplary temporal dynamics
“Healthy population” with a floater:breeder ratio of ~1 or higher (NEWTON 1988)
“Vulnerable population” without floaters
Functional traits: mass = 30 g, both habitats, all breeding types Landscape: medium shrub encroachment, medium clumping intensity
8
Animal Functional Type Model: Sensitivity analysis
population
floater
8
Animal Functional Type Model: Sensitivity analysis
“Healthy populations” are robust
“Vulnerable populations” are highly sensitive to dispersal-related parameters
number of explored territories
Animal Functional Type Model: Results
9
9
Animal Functional Type Model: Results
X X X
Herbivores and carnivores are sensitive to shrub encroachment
9
Animal Functional Type Model: Results
X X X
Herbivores and carnivores are sensitive to shrub encroachment
Small shrub-breeders are more vulnerable in grasslands with low clumping intensities
10
Animal Functional Type Model: Results
X X X
Insectivores and omnivores are sensitive to high clumping intensities Low bird numbers in encroached scenarios
10
Animal Functional Type Model: Results
X X X
Insectivores and omnivores are sensitive to high clumping intensities Low bird numbers in encroached scenarios
Smaller birds survive (at very low numbers) in encroached areas
11
Animal Functional Type Model: Conclusion
Conclusion » Populations without floaters have a higher extinction risk (NEWTON 1988, 1998, PENTERIANI et al. 2011, LENDA et al. 2012)
» Birds related to grassland are endangered due to shrub encroachment
» Surprisingly, birds related to bush thickets are also endangered due to
clumping intensity of shrubs and shrub encroachment » Small shrub-breeding birds are prone to extinction in grasslands
with low clumping intensities of shrubs » Smaller birds perform better in encroached areas compared to larger ones (supported by SEYMOUR & DEAN 2010)
Thank you for your attention … and thanks to my team for ideas, comments and help:
Florian Jeltsch, Niels Blaum & Volker Grimm
Animal Functional Type Model: References » ARCHER S. 2010: Rangeland conservation and shrub encroachment: new perspectives on an old problem. In: Wild Rangelands: Conserving Wildlife
While Maintaining Livestock in Semi-arid Ecosystems, pp. 53–97. J.T.D. TOIT, R. KOCK & J.C. DEUTSCH (Eds.). John Wiley and Sons Ltd, Chichester, United Kingdom. » CALDER III, W.A. 1983: Body size, mortality, and longevity. Journal of Theoretical Biology 102:133–144. » COETZEE B.W.T., L. TINCANI, Z. WODU & S.M. MWASI 2008: Overgrazing and bush encroachment by Tarchonanthus camphoratus in a semi-arid savanna.
African Journal of Ecology 46:449–451. » DONALDSON C.H. & D.M. KELK 1970: An investigation of the veld problems of the Molopo area: I. Early findings. Proceedings of the Annual Congresses of
the Grassland Society of Southern Africa 5:50–57. DOI: 10.1080/00725560.1970.9648610 » HOCKEY P.A.R., W.R.J. DEAN & P.G. RYAN 2005: Roberts birds of southern Africa, 7. Edition. New Holland Publishers, London, United Kingsdoms. » KRAAIJ T. & D. WARD 2006: Effects of rain, nitrogen, fire and grazing on tree recruitment and early survival in bush-encroached savanna, South Africa.
Plant Ecology 186:235–246.
Thank you for your attention
» LENDA M., B. MACIUSIK & P. SKÓRKA 2012: The evolutionary, ecological and behavioural consequences of the presence of floaters in bird populations.
North-Western Journal of Zoology 8:394–408.
» NEWMAN K. 2002: Newman's birds of southern Africa, 8. Edition. Struik, Cape Town, South Africa. » NEWTON I. 1988: Population regulation in peregrines: an overview. In: Peregrine Falcon populations: their management and recovery: 761–770. T.J.
CADE, J.H. ENDERSON, C.G. THELANDER & C.M. WHITE (Eds.). Peregrine Fund, Boise, Idaho. » NEWTON I. 1998: Population limitation in birds. Academic Press, London, United Kingdoms. » OTTAVIANI D., S.C. CAIRNS, M. OLIVERIO & L. BOITANI 2006: Body mass as a predictive variable of home-range size among Italian mammals and birds.
Journal of Zoology 206:317–330. » PENTERIANI V., M. FERRER & M.M. DELGADO 2011: Floater strategies and dynamics in birds, and their importance in conservation biology: towards an
understanding of nonbreeders in avian populations. Animal Conservation 14:233–241. » PRINZINGER R. 1993: Life span in birds and the ageing theory of absolute metabolic scope. Comparative Biochemistry and Physiology Part A: Physiology
105:609–615. » REISS M. 1991: The allometry of growth and reproduction. Cambridge University Press, Cambridge, United Kingdom. » SCHOLES R.J. & S.R. ARCHER 1997: Tree-grass interactions in savannas. Annual Review of Ecology and Systematics 28:517–544. » SEYMOUR, C.L. & W.R.J. DEAN 2010: The influence of changes in habitat structure on the species composition of bird assemblages in the southern
Kalahari. Austral Ecology 35:581–592. » SUTHERLAND G.D., A.S. HARESTAD, K. PRICE & K.P. LERTZMAN 2000: Scaling of natal dispersal distances in terrestrial birds and mammals. Conservation
Ecology 4:16.
