The latest news on breeding birds

You only have to compare this summer with last to realise how much things can change from one year to the next, both in terms of the weather and its effects on birds and other wildlife. Short term differences in bird populations and their breeding success are of interest to those studying such things but it is the longer term changes that are of wider interest. In the case of birds, information on how well the populations of many of our breeding species are doing comes from the BTO/JNCC/RSPB Breeding Bird Survey (BBS), the latest report from which has just been published.

As a volunteer myself, I appreciate the tremendous value of the survey and the importance of the information collected by the 2,592 volunteers who participate in BBS. Participation is simple enough, involving two visits to a survey square and the recording of what birds are seen and heard, and in what numbers. The survey, which began in 1995 as a replacement for the Common Birds Census operated by BTO, provides a measure of population change for a wide suite of species, highlighting those that have shown significant increases or decreases in their populations over time.

The latest report highlights the continued decline of turtle dove (down by 85% since 1995), cuckoo (down 50%), spotted flycatcher (down 49%) and starling (down 53%), among many others. Some species are, in contrast, increasing. These include: goldfinch (up 109%), blackcap (up 133%), nuthatch (up 88%) and great spotted woodpecker (up 139%). Not all of the increases are welcome, however, with Canada goose, greylag goose, ring-necked parakeet and red-legged partridge all showing sizeable increases in their populations.

One of the great strengths of the survey is that the information can be viewed at the regional level, something that has revealed some fascinating differences in how species have been doing. Cuckoo is one of several species in which populations in England are in decline but those in Scotland are stable or even increasing. There are a number of possible reasons why this might be happening, one of which is related to a changing climate, but more work is needed to be certain of what is going. Fortunately, the efforts of us volunteers provide the information needed to support this work.

Birdwatchers highlight partridge decline

Norfolk is partridge country, the one English county where the grey partridge retains something of a stronghold. Yet, even here, it is under threat and populations have continued to decline. New figures, just published for the Breeding Bird Survey, highlight a 40% decline since 1994 and an 87% decline since 1978. The species is now found on just 9% of the 2,879 sites covered as part of the survey, fewer than for red-legged partridge or pheasant.

The causes of the decline are well known, thanks to the vast amount of research carried out, making this one of the best studied of English birds. The grey partridge favours lowland farmland, using areas of mixed arable and grass leys, with uncultivated margins and hedgerows. Although the hens produce more eggs than any other British bird, typically 12-18, productivity has declined massively since the 1950s because of increasing pesticide use and decreasing amounts of predator control. In particular, the use of herbicides has reduced the availability of those invertebrates taken by partridge chicks after leaving the nest. By understanding what has driven the population decline it has been possible to develop prescriptions to manage farmland in a manner which favours the grey partridges. However, such prescriptions have only really been employed on traditional shooting estates, such as Holkham (which, incidentally, boasts the title of Britain’s premier partridge estate), with the wider countryside far from suitable. If we are to halt the decline in partridge numbers then we need to re-establish the network of hedgerows and field margins that are so important for this species.

That we are able to chart the changing fortunes of this and many other species, is down to the efforts and hard work of the thousands of birdwatchers who give up some of their time each year to participate in long-term surveys. One of the most important of these is the Breeding Bird Survey, administered centrally by the British Trust for Ornithology (BTO) and organised by voluntary regional organisers. Although the survey only began in 1994, the data collected can be compared directly with a previous BTO survey – the Common Birds Census – thanks to a period of overlap between the two, which allowed calibration of the two sets of information. Collectively, the surveys provide a long-term dataset, which can be used to monitor the changing populations of many bird species over a forty year period and across a wide range of habitats, something that is unique within the United Kingdom. For the grey partridge, the efforts of those birdwatchers participating in the Breeding Bird Survey provide a means by which we can evaluate the effectiveness of the conservation measures that are being put into action.