Analysing Population Numbers of the House Sparrow in the Netherlands With a Matrix Model and Suggestions for Conservation Measures |
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Authors: | Chris Klok Remko Holtkamp Rob van Apeldoorn Marcel E Visser Lia Hemerik |
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Institution: | (1) ALTERRA, Department of Ecology and Environment, Droevendaalsesteeg 3, P.O. Box 47, 6700, AA, Wageningen, The Netherlands;(2) Biometris, Department of Mathematical and Statistical Methods, Wageningen University, P.O. Box 100, 6700, AC, Wageningen, The Netherlands;(3) Department of Innovation and Environmental Sciences Copernicus Institute, Utrecht University, P.O. Box 80.115, 3508, TC, Utrecht, The Netherlands;(4) ALTERRA, Department of Ecology and Society, Droevendaalsesteeg 3, P.O. Box 47, 6700, AA, Wageningen, The Netherlands;(5) Netherlands Institute of Ecology (NIOO-KNAW), Centre for Terrestrial Ecology, P.O. Box 40, 6666, ZG, Heteren, The Netherlands |
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Abstract: | The House Sparrow (Passer domesticus), formerly a common bird species, has shown a rapid decline in Western Europe over recent decades. In The Netherlands, its
decline is apparent from 1990 onwards. Many causes for this decline have been suggested that all decrease the vital rates,
i.e. survival and reproduction, but their actual impact remains unknown. Although the House Sparrow has been dominant in The
Netherlands, data on life history characteristics for this bird species are scarce: data on reproduction are non-existent,
and here we first present survival estimates based on live encounters and dead recoveries of marked individuals over the period
1976–2003, 14 years before and 14 years during the decline, reported to the Dutch Ringing Centre. We show that there is an
indication that both juvenile and adult survival are lower during the period of decline.
Secondly, to be able to analyse the relative impact of changes in the vital rates, we formulated a general matrix model based
on a range of survival values between zero and one with a step size of 0.01 (both juvenile and adult yearly survival) and
a range of realistic reproduction values (one, three or five fledglings per pair per year). With the matrix model, we calculated
the finite rate of population change (λ) and applied elasticity analysis. To diagnose the cause of the decline in the Dutch
House Sparrow, we parameterised the model with estimates of survival values before and during the decline and present the
resulting λ. With the survival estimates from the declining period, λ < 1 only if reproduction is relatively low. We discuss this result within the light of available literature data on survival
in the House Sparrow. Finally, we evaluate which of the suggested causes of population decline should be reversed to mitigate
the decline and how this can be achieved. |
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Keywords: | conservation MARK matrix model survival |
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