Birds Battle for Nesting Sites
It isn’t difficult to understand why it is farmland birds which have suffered the greatest decline in number over recent decades. Intensive farming practices have meant that a huge proportion of these birds’ natural habitat has simply disappeared. Hedgerows have been removed to enable farmers to plant crops right up to the margins of the fields whilst pesticides and fertilisers reduce the number of insects for birds to feed on. New approaches to agriculture have meant that there are fewer winter stubbles.
But the loss of habitat doesn’t explain why certain species are faring much worse than other closely related species which live in the same environment.
Scientists have been studying farmland birds to discover why some species are declining more rapidly than others. It is now believed that the competition for nesting sites could explain the situation. Research suggests that the birds which nest in early spring are claiming the available nesting sites at the expense of species which breed later in the season.
With many potential nesting sites having been removed, the birds are competing for far fewer suitable sites. Those who arrive first claim most of these, leaving nowhere for late arrivals to nest.
New research into Nesting Habits
A study conducted by the University of Exeter looked at population changes in over 200 different species around the world. The data was combined with a mathematical model that used game theory to predict the likely behaviour of the birds when faced with competition for nesting sites.
The study found that larger species that nest early generally do much better than smaller species which nest later in the year. This would explain why the chaffinch is doing well in the UK whilst the goldfinch is in decline.
Many conservation efforts have focussed on supplying food to birds but it would appear that a more holistic approach is now required. The restoration and provision of nesting sites is just as important, if not more so. The measures which could be employed could be as simple as delaying the cutting of hedgerows until the breeding season is over or providing more nesting boxes for the birds to use.
There are no quick fixes but the decline of several species could be halted and then reversed if more nesting sites are made available.