Ecological Modelling 224 (2012) 54–64 Contents lists available at SciVerse ScienceDirect Ecological Modelling journa l h o me pa g e: www.elsevier.com/locate/ecolmodel The response of the woodpigeon (Columba palumbus) to relaxation of intraspecific competition: A hybrid modelling approach Suzanne M. O’Regan a,∗ , Denis Flynn a , Thomas C. Kelly b , Michael J.A. O’Callaghan a , Alexei V. Pokrovskii a , Dmitrii Rachinskii a a School of Mathematical Sciences, Western Gateway Building, Western Road, University College Cork, Cork, Ireland b Department of Zoology, Ecology and Plant Science, Distillery Fields, North Mall, University College Cork, Cork, Ireland a r t i c l e i n f o Article history: Received 9 June 2011 Received in revised form 1 October 2011 Accepted 19 October 2011 Available online 25 November 2011 Keywords: Climate change Density-dependence Hybrid model Intraspecific competition Semi-discrete model Woodpigeon a b s t r a c t The recent rapid growth of the woodpigeon population in the British Isles is a cause for concern for environmental managers. It is unclear what has driven their increase in abundance. Using a mathe- matical model, we explored two possible mechanisms, reduced intraspecific competition for food and increased reproductive success. We developed an age-structured hybrid model consisting of a system of ordinary differential equations that describes density-dependent mortality and a discrete component, which represents the birth-pulse. We investigated equilibrium population dynamics using our model. The two hypotheses predict contrasting population age profiles at equilibrium. We adapted the model to examine the impacts of control measures. We showed that an annual shooting season that follows the period of density-dependent mortality is the most effective control strategy because it simultaneously removes adult and juvenile woodpigeons. The model is a first step towards understanding the processes that influence the dynamics of woodpigeon populations. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The woodpigeon, Columba palumbus, is a multi-brooded her- bivore and therefore likely to benefit from global warming and climate change (Jiguet et al., 2007). It is a well-known agricultural pest, which has appeared to have benefitted from changing agricul- tural practices, particularly in Britain (Inglis et al., 1990). The pest status of woodpigeon led to a detailed research programme into its biology and management in the 1960s (Murton, 1958, 1961, 1965, 1971; Murton et al., 1964, 1966, 1974; Murton and Isaacson, 1964). During this period, the population was reasonably stable, although large fluctuations in numbers occurred within years, i.e., the popu- lation increased rapidly over the breeding season and then declined drastically during the winter months so that the total observed each year remained relatively constant. The amount of grain available determined numbers that survived after the breeding season until the period when woodpigeons switched to their clover food sup- ply in December. Juveniles required grain to aid their development in the months after fledging whereas adults could more readily consume less nutritious clover leaves. The timing of the mini- mum in woodpigeon numbers occurred in February and March, ∗ Corresponding author. Present address: Odum School of Ecology, University of Georgia, Athens, GA 30602-2202, USA. Tel.: +1 706 583 5538. E-mail addresses: smoregan@uga.edu, s.m.oregan@gmail.com (S.M. O’Regan). i.e., the period of least plentiful clover stocks. When food supplies became depleted, the effects of intraspecific competition inten- sified and were density-dependent (Murton et al., 1966, 1971), i.e., if the size of a flock was high relative to the quantity of food available, then mortality was higher. Mortality principally affected subordinate individuals and juveniles. It is important to note that during the period of Murton’s studies, winters were noticeably longer and colder than in the period 1976–2000 (Houghton et al., 2001). The recent increase in the woodpigeon population of the British Isles (Baillie et al., 2009; Crowe et al., 2010) has become a cause for concern for agriculture (Tayleur, 2008), but also for aviation safety, because the species is increasingly involved in birdstrikes (Kelly et al., unpublished data). The exact reasons for this increase are unknown (Saari, 1997). One hypothesis is that climate change has induced the earlier onset of the growing season (Carroll et al., 2009; Donnelly et al., 2009; Menzel et al., 2006; Møller et al., 2010). Since the food supply does not fluctuate to the same extent as it did in the 1960s, food is more readily available to woodpigeons through- out the year. Consequently, woodpigeon numbers are no longer regulated by natural fluctuations of the food supply, as they were before the onset of climate change. Therefore, decreased intraspe- cific competition for food during winter may be the mechanism behind the sustained increase. Alternatively, woodpigeons may be particularly adapted to benefit from climate change because they are multi-brooded; the ability to produce multiple broods per year, 0304-3800/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolmodel.2011.10.018