2012 preliminary UK Nest Record Scheme (NRS) results from BTO

Full news report and tables from BTO here

The BTO publishes preliminary results each Autumn to provide an initial assessment on the UK’s bird breeding season prior to the publication of the annual BirdTrends Report the following year. Producing results so soon after the breeding season is only possible thanks to NRS participants’ speedy submission of data.

Record-breaking rainfall

To say it was a wet spring and summer this year is an understatement. UK Met Office rainfall totals for England & Wales in two months were the highest on record, with four times the average falling in April and twice the average falling in June. If the adverse weather affected nesting birds, it also made life difficult for volunteers, resulting in many cancelled field sessions and missed nest visits. However, thanks to the dedication of the nest recorders, over 25,000 records were submitted in time for the preliminary report and 2012 breeding performance figures have been produced for 25 species.

Early breeders advance, late breeders delay

Conditions in February and March were actually warmer and drier than average, and many of the early resident breeders, including tawny owl, song thrush and long-tailed tit, commenced nesting significantly earlier than the five-year average. In contrast, long-distance migrants travelling northwards from their African wintering quarters the following month had to contend with a succession of severe weather systems across Europe and were greeted by cold, wet weather when they finally returned to their breeding grounds. As a result, laying dates of all six species for which preliminary results are produced were significantly delayed relative to the average for the preceding five years. Laying dates of short-distance migrants, blackcap and chiffchaff, which winter in the Mediterranean and therefore return to breed earlier, were no later than average.

Caterpillar-dependent residents struggle

Feedback from lepidopterists suggest that 2012 was a very poor year for moths and species that rely heavily on caterpillars as a source of food for their nestlings experienced a sharp drop in productivity. The average number of fledglings produced per breeding attempt for both blue and great tit was significantly below average, the latter experiencing the second worst season on record. This poor performance was influenced by small clutches and high failure rates during incubation, as well as by a reduction in brood sizes, suggesting that adults were in poor condition when breeding commenced. The number of chaffinch fledglings per nest was at its lowest level since records began in 1966, by some margin. Losses during incubation were high and heavy rainfall may have had a direct impact, wetting the eggs when the female left the nest to feed.

A poor vole year

Many of the lowland owls and raptors feed primarily on volves, which anecdotal evidence suggests were in short supply during 2012, although the extent to which this paucity was influenced by the adverse weather conditions is not yet clear. However, heavy rainfall almost certainly affects the accessibility of these prey items, making it difficult for birds to hunt. Fledgling numbers of all three species for which preliminary trends are produced (kestrel, tawny owl and barn owl) were below average, although this difference was significant only for kestrel.

Flooding and water-logging

Exceptionally high levels of rainfall directly impacted on those species whose nests are vulnerable to flooding. Reed warbler is the most obvious example, demonstrating a significant reduction in every aspect of its breeding success as a result of rising water levels in ponds and lakes, leading to a fall in fledgling production of almost 36%. Increased river flow may also have contributed to the increase in failure rates of dipper nests during incubation.

Poor prospects for fledglings?

The results of the preliminary NRS analyses are broadly consistent with those of the BTO’s Constant Effort Scheme (CES), which calculates breeding success by comparing the numbers of adult and juvenile birds ringed each year at 120 sites across Britain & Ireland. However, there are some species (long-tailed tit, willow warbler) for which CES records a much more marked reduction in productivity during 2012. This difference suggests that young birds may have continued to struggle after leaving the nest, their lack of experience and relatively poor quality plumage making it much harder for them to cope with extreme weather conditions, leading to a drop in survival rates post-fledging.

Long-term impacts

Many of the species for which preliminary trends have been calculated are capable of producing large numbers of offspring each year, and so have the potential to bounce back rapidly following a poor breeding season provided conditions improve. However, the extreme conditions in 2012 resulted from a shift in the jet stream and it is difficult to predict how its position may be influenced by future climatic warming and the melting of the Arctic icecaps. If wet summers become more frequent, then we may witness long-term changes in the numbers of some bird species.

– including an average of 50 house sparrows every hour…

Report from British Birds

Since 1966, the UK has lost breeding birds from the countryside at an average rate of a nesting pair every minute, say conservationists in The State of the UK’s Birds 2012, published on Monday 19^th November.

The report estimates that there are 166 million nesting birds in the UK, compared with 210 million nesting birds in 1966. The house sparrow has seen one of the greatest losses of any bird in the UK. Although since 2000 house sparrow numbers have started to increase, the UK still has 20 million fewer sparrows than it did in 1966. The current population is estimated at around 10 million.

One of the report’s authors, Dr Mark Eaton of the RSPB said: “It is shocking to think that we’ve lost one in five of the individual birds that we had in the 1960s, especially when you think that the 44 million birds we have lost since 1966 is equivalent to the current adult human population of England and Wales.”

There have been many changes in the UK which have affected birds, most notably changes in the land use and the management of the countryside and seas – these can change the amount or quality of key resources needed by birds, such as suitable places to nest or a shortage of food in summer or winter. However, for some species, including the house sparrow, the precise reasons behind these declines aren’t fully understood.

The changing fortunes of two, related species further highlight the changes to the UK’s birds: the turtle dove and the collared dove. In 1966, the turtle dove was still a widespread bird with about 140,000 breeding pairs, whilst numbers of the collared dove were very low, as the species only began nesting in the UK in 1955. Today there are only thought be around 14,000 pairs of turtle dove nesting in the UK, whereas the collared dove had exploded to around one million pairs.

Cold weather is thought to have had a startling effect on bird numbers too. The wren, for example – still the UK’s most numerous bird – has lost an average of 835 individuals a day since 2000. But another garden bird, the chaffinch, has increased at a rate of 150 individuals per day.

Dr Andy Musgrove of the BTO, who worked on compiling these figures, said “We have learnt a great deal about bird numbers in the UK and, particularly, how they have changed through time. Amongst individual species, whilst there have been some winners, the number of losers is greater and the long-term picture is sobering. There is still more to learn though, and we need the continuing support of ever greater numbers of volunteer birdwatchers, on whose efforts all of these numbers are based”.

The State of the UK’s Birds report is a great example of ‘citizen science’ in action. Most of the information upon which the report is based is derived from the efforts of a network of skilled, volunteer ornithologists who contribute to national monitoring schemes like the UK’s Breeding Bird Survey and Wetland Bird Survey. Such schemes provide a high quality evidence base underpinning the work of government, conservation organisations and land managers in their joint efforts to conserve the natural environment and its wildlife. Here in Jersey we too rely on volunteer observers sending in their sightings to the Bird Recorder at the Société Jersiaise Ornithology Section. We in turn compile an annual Bird Report each year (copies are available from The Museum in St Helier and from the Durrell Visitor Centre). The Ornithology Section also takes part in most of the UK’s bird monitoring schemes such as the Breeding Bird Survey and BIRDS ON THE EDGE includes a bird monitoring project. Channel Islands bird numbers are not included in The State of the UK’s Birds 2012 but the current status of Jersey’s bird populations can be seen in our own report Conservation Status of Jersey’s Birds: Jersey’s bird populations in the 21^st Century.

The State of the UK’s Birds 2012 is produced by RSPB, British Trust for Ornithology and the Wildfowl & Wetlands Trust – and the UK Government’s statutory nature conservation. The report also includes the latest information on the number of ducks, geese, swans and wading birds spending the winter in the UK and an update on the internationally-important birds, including albatrosses and penguins, on the UK’s overseas territories.

The State of the UK’s Birds 2012 can be downloaded from the British Trust for Ornithology.