Impact of land cover characteristics on residential diurnal raptor abundance in the agricultural Sudano-Sahelian region © Ralph Buij Deborah Nicole Winkel Student number: 0455253 e-mail: [email protected] Program: Sustainable Development Track: Landuse, Environment and Biodiversity Supervisors: Dr. ir. M.G. Rietkerk Drs. R. Buij Dr. H.H. de Iongh Date: July 31, 2009 1 2 Impact of land cover characteristics on residential diurnal raptor abundance in the agricultural Sudano-Sahelian region Deborah Winkel August 2008 – July 2009 Centre d‟Etude de l‟Environnement et du Développement au Cameroun (CEDC) Department of Environment and Development, Centre of Environmental Sciences (CML), Leiden Utrecht University © 2009 Deborah Winkel Cover photo Ralph Buij: Rüppell‟s Griffon Vulture (Gyps rueppellii), Extreme North province, Cameroon 3 4 Utrecht University Faculty of Geosciences Department of Innovation and Environmental Sciences Programme Science & Innovation Management Programme Sustainable Development Statement of Originality Student’s name: Deborah Nicole Winkel Student’s ID: 0455253 Title report / thesis: Impact of land cover characteristics on residential diurnal raptor abundance in the agricultural Sudano-Sahelian region. I declare that: - this is an original report / thesis and is entirely my own work, - where I used the ideas of other writers, I acknowledge the source in every instance, - where I used any diagrams or visuals, I acknowledged the source in every instance, - this thesis (or part of it) was not and will not be submitted as assessed work in any other academic course. Date of signature:.............................................................................................. Student’s signature: .......................................................................................... 5 6 Preface This study is performed within the framework of a PhD study of R. Buij executed in collaboration between the Institute for Environmental Sciences of the Leiden University in the Netherlands (CML) and the Centre for Environment and Development Studies in Cameroon (CECD). This report was done for my master thesis for the master Sustainable Development, track Land use, Environment and Biodiversity at Utrecht University. The fieldwork which provided the base for this report was conducted at the CEDC, which is a joint cooperation between the CML in the Netherlands and the University of Dschang, Cameroon. The author wishes to thank her friends and family for all their support and motivation. Also, I would like to thank H. de Iongh and M. Rietkerk and for their assistance and comments during the writing of the proposal and this final report and K. Musters for his help with the statistics. My special thanks goes to R. Buij and D.J. van der Goes for helping throughout the entire process between writing the proposal until writing this final report. I would like to thank them, together with B. Croes, for the great conversations, good laughs, friendship, horseback rides and horrible movies during and in between our fieldwork trips. My gratitude also goes to the entire staff of the CEDC in Cameroon, specifically my driver Hamidou, who helped me a lot with my French, had a great sense of humor, helped me with counting crickets I otherwise might have missed, and let me enjoy many great traditional lunches at his home. Salomon: while being the only student at the CEDC you‟ve been of a great mental support and I really enjoyed the coffee you made. Lawane and Inez: I‟m very grateful for your help in learning more about the city and it‟s market, local research, the local places to eat and the introduction to my seamstress. I‟m am also very grateful for the financial and mental support given by my parents Jan N. Winkel en J.K. Serné. Thank you and my brother B.G. Winkel for visiting me in the period in Cameroon that was toughest: I had a great time. Furthermore, I would like to thank Utrecht University and the H.G. Boumeester stichting for financing part of the research. Last I would specifically like to thank D.J. van der Goes for all his help with my research, going as far as entering data while lying in the hospital. 7 Abstract Dry-season counts of diurnal raptors were performed in the wet season in the agricultural region in northern Cameroon along several road transects (total = 900 km), while assessing general land cover characteristics and land cover characteristics of the raptor habitats. 9 common diurnal residential raptor species (Milvus migrans, Elanus caeruleus, Melierax metabates, Falco alopex, Butastur rufipennis, Necrosyrtes monachus, Buteo auguralis, Gyps rueppellii, Aquila wahlbergi) have been analyzed for their land cover preference at microhabitat scale regarding several land cover characteristics: agriculture, woodland, village, herbaceous layer, trees and shrubs/bushes. Overall all raptors, except Necrosyrtes monachus and Milvus migrans, showed, on a microhabitat scale level, a significant preference for a high percentage of natural woodland. Conservation of the woodland areas within the agricultural region is thus important for preservation of many raptors: only the scavenging raptors living of dead animals and refuse dumps significantly prefer villages above woodland and agricultural fields. Human presence may not be a problem for several raptors, but their activities might. For cover with agriculture and trees, there is a wide variety in preference, varying from a low level (resp. 0-20% and 0-30 trees/hectare) to a high level (80-100% and >120 trees/hectare). On a microhabitat level, many of the investigated raptors seem to prefer a small cover of herbaceous layer above a larger cover, indicating that on a small scale, grazing can be possibly be positive for raptors, when bare soil is surrounded by areas with more grass. Regarding bush/shrub density, there was little variation in the area (88% having a cover of 0-20%), where only Necrosyrtes monachus and Buteo auguralis showed a significant preference for respectively a low to high cover. Maintaining a diverse landscape with a wide diversity in land cover characteristics is thus expected to be crucial for conservation of raptors. Through field experiments, I investigated the effect of very local land cover characteristics on the presence of prey animals for raptors, during the dry season. Literature shows that a wide variety of food types are eaten by different raptors. Analysis in 4 different land use types revealed that in each land use type, grasshoppers had a statistically significant positive correlation with the grass cover. In natural woodland, average grasshopper numbers found were significantly higher than in villages and cotton plantations. Differences are expected to be larger in the growth season (wet season): in the dry season no significant differences were found between the intensive (cotton) plantations and the extensive (sorghum plantations), regarding grasshopper densities. For other types of prey animals, no significant relations have been found regarding land cover characteristics. Only in general, significantly more lizards were present in villages compared to the other three land use types. Résumé Les comptages en saison sèche des rapaces diurnes ont été effectué en saison des pluies dans le nord de la région agricole du Cameroun le long de plusieurs tronçons de route (un total de 900km) tout en évaluant les caractéristiques générales de couvertures du sol ainsi que celles des habitats des rapaces. Neuf espèces communes de rapaces diurnes résidente (Milvus migrans, Elanus caeruleus, Melierax metabates, Falco alopex, Butastur rufipennis, Necrosyrtes monachus, Buteo auguralis, Gyps rueppellii, Aquila wahlbergi) ont été analysé quant à leurs préférence de couverture du sol au niveau du micro-habitat en utilisant plusieurs caractéristiques: agriculture, régions boisées, strate herbacée et buissons/arbustes. Tout les rapaces, sauf Necrosyrtes monachus et Milvus migrans, on démontrés au du micro-habitat une préférence significative pour un haut pourcentage de région boisées naturelles. La conservation des régions boisées situé à l'intérieure de la région agricole est donc importante pour la préservation de plusieurs rapaces: seul les rapaces charognards se nourrissant d'animaux mort et de détritus préfèrent significativement les villages au détriment des régions boisées et des champs agricoles. Pour plusieurs rapaces la présence humaine n'est probablement pas un problème, mais leurs actions pourraient l'être. Pour la couverture avec agriculture et arbres, il y a une grande variété en ce qui à trait à la préférence, variant d'un niveau bas (resp. 0-20% et 0-30 arbres/hectare) jusqu'à un niveau élevé (80-100% et >120 8 arbres/hectare). Au niveau du micro-habitat plusieurs des rapaces étudiés semblent préférer une couverture herbacée de petite taille aux couvertures plus grandes, indiquant qu'à petite échelle, le pâturage pourrait être positif pour les rapaces lorsque qu'un sol dénudé est entouré d'endroit avec plus d'herbes. En ce qui a trait à la densité d'arbustes et de buissons, il y avait peu de variations dans la zone étudiée (88% ayant une couverture de 0-20%) où seulement Necrosyrtes monachus and Buteo auguralis avaient une préférence significative respectivement pour une couverture basse et haute. On peut donc s'attendre à ce que maintenir un paysage diversifié avec une grande variété de caractéristiques de couverture de sol soit crucial pour la conservation des rapaces. À l'aide d'expériences sur le terrain, j'ai étudié l'effet