Songbird nesting success

We have been monitoring the nesting success of some songbird species for several years, both at Loddington and at two local comparison sites. 

Our main study species are blackbird, song thrush, dunnock, whitethroat, chaffinch and yellowhammer.  This research reveals that, while habitat and weather influence nest survival of some species at certain nesting stages, overall nest survival is correlated with abundance of crows and magpies which appear to be the main predator. 

We are currently exploring these data more fully, through a PhD project being conducted by Patrick White.  His analysis incorporates data collected in the recent period in which predators have not been controlled (since 2002), as well as the earlier data.  The most recent analysis reveals that predator is the main influence on nest survival, although there is also a strong influence of year. 

What has happened for many species is that nesting success has declined from 1993 to 2001, as songbird breeding numbers have increased.  This could be explained as a density dependent effect, with predators concentrating more on nests as a source of food when they were abundant. 

This work is continuing, but the implication is that, while predator control may contribute to restoring breeding numbers of some species initially, the influence is not maintained when higher songbird numbers are established.