Rapid increase in numbers and change of land-use in two expanding Columbidae species(Columba palumbus and Streptopelia decaocto)in Algeria

Background: Investigating population ecology of urban bird species,particularly the invasive and expending spe?cies,is the key for the success of urban management and planning strategies.Methods: Populations of two Columbidae species,the Woodpigeon(Columba palumbus) and the Eurasian Collared Dove(Streptopelia decaocto),were monitored from 1992 to 2010 in the Algiers Sahel,the Mitidja Plain and surround?ing areas(Northern Algeria).Monitoring of species densities was performed by the mapping?plot method.The foraging flight routes of Woodpigeon and the distribution of Eurasian Collared Dove were assessed by systematic observations.Results: The number of counted birds was statistically constant at first years of the survey,and then increased sig?nificantly,beginning from low numbers,their densities accelerated sharply between 2001 and 2006,then reached to an equilibrium state.The significant increase in Woodpigeon's population could be explained by the reduced hunt?ing pressure and by species adaptation to new food resources provided by nearby agriculture.Indeed,monitoring of flight directions of the species revealed the use of agricultural landscapes and habitats,which is a good indicator explaining adaptation and trophic niche of the species.The occurrence of the Eurasian Collared Dove in Algiers began in 2000.Its density experienced a rapid increase with similar trend pattern as that of Woodpigeon.Its distributional range is confined mainly in suburban environments of the Mitidja Plain.Conclusion: The modifications of habitats,urbanization increase and the lessening of hunting in the Mitidja Plain facilitated the rapid expansion of the Eurasian Collared Dove and Woodpigeon as well contributed to the increase in their numbers over time.

Effects of human disturbance on nest placement of the woodpigeon (Columba palumbus): a case study from the Middle Atlas, Morocco

The woodpigeon(Columba palumbus)is a common and widespread bird in Morocco(North Africa).I exam­ined,over 2 years(2010 and 2011),the breeding density and nest placement of this game species in relation to nest site habitat and degree of human disturbance.The study area was in the Middle Atlas Tighboula moun­tain forest,Morocco,in a disturbed and an undisturbed site.Using data collected in the 2 study sites,I aimed to identify the factors influencing the placement of nests within holm oak trees(Quercus rotundifolia)and their densities.I found that habitat structures,influenced by grazing disturbance,have affected nesting density and the location of nests of this species.Woodpigeons place their nests in a higher position(3.42±0.19 m)when disturbance intensity is high and lower(1.68±0.1 m)when disturbance intensity is low,and show higher nest­ing density in less disturbed zone(3.1±0.4 nests/ha)than in highly disturbed zones(1.4±0.2 nests/ha).Graz­ing disturbance could pose a threat to population persistence at a broader scale and could potentially reduce the abundance of this species by altering the composition and the structure of the forest nesting habitat.Further multi-scale studies are needed to assess the effects of different levels of grazing disturbance on woodpigeon nest density and placement,and to enhance our knowledge of the breeding behavior of this game species under vari­able environments.