Even Great Tits Show Their Age

Great Tits Also Have Age-Related Defects

Great Tit (Parus major)

The offspring of older great tit females are much less successful than those of younger mothers. Things mainly go wrong in the later stages of the upbringing, concludes evolutionary biologist Sandra Bouwhuis. For great tit females, it turns out to be a good idea to invest in generating offspring in the first years of life. Bouwhuis will be awarded a PhD by the University of Groningen on 18 March 2011 for her research into the aging of great tits.

Bouwhuis researched aging under female great tits (Parus major) in Wytham Woods (Oxfordshire, UK) and on the island of Vlieland (NL). She investigated the number of eggs and offspring and the reproductive success of this offspring, among other things.

Although great tits can live for nine years, breeding success declines rapidly after the age of two. Nevertheless, older great tits keep on breeding every year, says Bouwhuis: 'They carry on to the bitter end'. What is remarkable is that at the start of the breeding period there's very little difference between the nests of older and younger females. Bouwhuis discovered, however, that massive mortality occurs just after the young leave the nest. 'The parents still have to guide their young in the first crucial weeks after leaving the nest. Perhaps the older mothers have more trouble with that guidance; their young often fall prey to sparrowhawks, for example. Or maybe the older mothers have only been able to find less suitable places in the woods....'

Speaking of great tits, the Chinese seem to value them as well:

I can't understand what they're saying, but some of the diagrams seem to promise something biologically unlikely: