Publication details
Effect of sex, age and social status on the mortality risk of the grey partridge
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| Year of publication | 2011 |
| Type | Article in Proceedings |
| Conference | XXXth IUGB congress (International Union of Game Biologist) and Perdix XIII 5th-9th September 2011 |
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| Citation | |
| Description | Mortality in birds is known to vary with the stage of life cycle, sex, age and social status of an individual. In the grey partridge (Perdix perdix), only females incubate large clutches and thus invest more than males into reproduction whereas males are more active in pairing prior to the breeding period. Older individuals can benefit from previous experience during pairing and nesting, but they are also burdened with costs of previous reproduction and survival. The birds are exposed to hard winter conditions, a period with reduced food supply and cover. On the other hand, aggregating in coveys and increased vigilance during this period can reduce predation risk. Adult sex ratio in grey partridge populations is moderately skewed towards a male surplus, which is a supposed result of generally higher mortality of hens. We analysed recent survival data of 169 radio-tracked grey partridges from three different areas in the Czech Republic (A: 2002-2003, B: 2003-2004, C: 2009-2010), using models of Cox’s proportional hazard. We found that the mortality risk varied within the year, being the lowest during the covey period (autumn to winter) without any significant effect of sex and age. Mortality increased during the pairing period (late winter to early spring) with similar mortality in both sexes, but significant effect of age. Older (more experienced) individuals survived better, probably due to less time spent pairing compared to yearlings. Mortality increased again during the nesting period when females died significantly more than males. Males had lower mortality throughout the year (25% lower than females) which may cause the male surplus (10-18%) in our studied populations. The results are essential to allow reliable modeling of population dynamics of grey partridge populations in modern agricultural landscapes. |