2010/05/01 by Stavros M. Xirouchakis, Stavros Xirouchakis · 6 citations
Environmental Science · Agricultural and Biological Sciences · Immunology and Microbiology · #Avian ecology and behavior #Animal Behavior and Reproduction #Bird parasitology and diseases
paper · pdf · doi:10.1080/00063650903505754
Capsule While breeding dates were similar to those of populations in other Mediterranean regions, there is evidence of either a low carrying capacity or insular traits, and the population seems to experience a bottleneck period during the chick‐rearing period. Aims To describe the breeding phenology of Griffon Vultures in Crete, assess their breeding success and productivity, and compare breeding dates and parameters with mainland populations. Methods The breeding ecology of Griffons was studied between 1997 and 2001 by intensively monitoring 70 focal nests, whereas the timing of laying was determined in 86% of the breeding population. The reproductive performance was assessed from1996 to 2005 by visiting all active colonies five to nine times per year. Breeding parameters were compared between years and regions by applying a mixed design repeated‐measures anova. Results The mean laying date was 28 January (range: 25 December–16 April) with clutches peaking in February (86%). Median laying date in west and east Crete were 17 January and 7 February respectively, preceding the rainfall season. The average incubation period was 57 ± 4 days and hatching events occurred from 15 February to 29 April. The nestling stage lasted 119 ± 9 days and fledging dates ranged from 4 June to 23 August. The breeding success was 0.74 chicks/breeding pair/year and productivity was 0.52 chicks/territorial pair/year. Fifty percent of the breeding failures occurred during the egg stage, 16% during hatching and 34% during the chick‐rearing period. Conclusion Breeding success was mainly influenced by fledging success, negatively affected by inclement weather in spring, and decreased in relation to laying date and age of mate. A density‐dependent mechanism in combination with environmental stability seemed to diminish interregional differences in breeding parameters. Thirty‐five percent of the colonies produced 76% of all the young fledged in 10 years. An artificial increase of food supplies during the prelaying and the mid chick‐rearing periods could improve the species breeding performance.