By Prof. Chris Stoate, Allerton Project Head of Research
The annual monitoring of breeding songbirds at the Allerton Project now represents a long-term dataset spanning 33 years. Overall songbird numbers remain around 70% higher than they were at the start of the project in 1992.
This long-term dataset provides an exceptional insight into how bird numbers can respond to suitable management at the farm scale. From this annual monitoring, combined with more intensive research, we know that some species are influenced by predator numbers, others by the availability of food in winter, and others directly by the habitat available to them. There are also interactions between these various influences.
Other species have been affected by processes operating beyond the farm boundary, at the regional and national scales. For these species, farm-scale management is unlikely to have an influence on local breeding numbers.
For migratory species, factors operating in the wintering areas, or on migration routes, play an important role, but again, the extent to which this is the case varies between species, including those that are closely related and share similar niches in their breeding range. My research in West Africa some years ago sheds light on this and we have recently produced a research brief summarising the findings in the context of birds monitored at the Allerton Project.
The broader issue of how these various factors influence breeding abundance of a range of songbird species is discussed in much more detail in my book.