Diet composition influences annual breeding success of Montagu's Harriers Circus pygargus feeding on diverse prey: Capsule Diet diversity was positively related to nest failure in Montagu's Harriers

Publication Type:Journal Article
Year of Publication:2006
Authors:Arroyo, BE, García, JT
Journal:Bird Study
Volume:53
Date Published:2006
ISBN Number:0006-3657
Keywords:Accipitridae, Circus, Circus pygargus, Spain
Abstract:Aims To evaluate whether breeding density, age structure and breeding success of Montagu's Harriers were related to variations in diet composition. Methods Breeding data were collected over an eight-year period (1991?98) in Madrid, central Spain. Diet was evaluated through pellets and remains collected near nests. Diet diversity was calculated using Shannon's index. Results Diet diversity was negatively correlated to the proportion of hares Lepus granatensis in the diet, positively to the proportion of insects, and not significantly to other prey types. Breeding parameters varied significantly between years, although annual variation in breeding parameters in Madrid was lower than in populations where diet is less diverse. Nest failure was the most important variable explaining variation in productivity, and was primarily caused by food-related factors (abandonment and starvation). Nest failure was less frequent in years where diet diversity was lower. Conclusion Hares appear to be the preferred prey for Montagu's Harriers in Madrid, and other prey were used mainly when hares were less abundant or less available (with insects being the main alternative prey). Years when diet was less diverse (i.e. when hares were dominant in the diet) were associated with a higher productivity, and with a lower between-pair variation in this parameter.Aims To evaluate whether breeding density, age structure and breeding success of Montagu's Harriers were related to variations in diet composition. Methods Breeding data were collected over an eight-year period (1991?98) in Madrid, central Spain. Diet was evaluated through pellets and remains collected near nests. Diet diversity was calculated using Shannon's index. Results Diet diversity was negatively correlated to the proportion of hares Lepus granatensis in the diet, positively to the proportion of insects, and not significantly to other prey types. Breeding parameters varied significantly between years, although annual variation in breeding parameters in Madrid was lower than in populations where diet is less diverse. Nest failure was the most important variable explaining variation in productivity, and was primarily caused by food-related factors (abandonment and starvation). Nest failure was less frequent in years where diet diversity was lower. Conclusion Hares appear to be the preferred prey for Montagu's Harriers in Madrid, and other prey were used mainly when hares were less abundant or less available (with insects being the main alternative prey). Years when diet was less diverse (i.e. when hares were dominant in the diet) were associated with a higher productivity, and with a lower between-pair variation in this parameter.
URL:http://www.tandfonline.com/doi/abs/10.1080/00063650609461418
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith