Similar patterns of age-specific reproduction in an island and mainland population of great tits Parus major
Bouwhuis S., Van Noordwijk AJ., Sheldon BC., Verhulst S., Visser ME.
The process of ageing was long thought to be too infrequent to affect life-histories in natural populations. Long-term studies have, however, recently demonstrated ageing to be ubiquitous even in the wild, although confounding factors, such as emigration instead of mortality, or inter-population variation in rates of ageing have seldom been addressed. Here, we present analyses of female age-specific reproductive performance in a Dutch island population of great tits Parus major. For this population with limited connectivity to surrounding areas, we show that, between individuals, reproductive lifespan positively co-varies with recruit production, while within individuals performance improves up to 3 years of age, after which it gradually declines. We also show these patterns to be strikingly similar to those recently found in a less isolated British mainland population of great tits, characterised by different environmental conditions and life-history strategies, in particular the frequency of multiple breeding. Our results therefore suggest patterns of age-specific reproductive performance to be robust to both environmental and life-history variation. © 2010 The Authors.