27 August 2015

How to get up close to a ringer

Gary Clewley writes:

Another year and another Birdfair at Rutland Water has come and gone. The bird ringing demonstration proved to be very popular again with people (and especially families) regularly able to get up close and see the process of ringing first hand. In total, around 175 birds from over 20 species were ringed or recaptured over the course of the weekend. This gave us the opportunity to show people how ringers are able to identify and age birds in the hand as well as explaining why ringing and nest recording are essential for monitoring how and why populations are changing.
Great way to get close and learn about our 'British' birds - Stephen McAvoy

Some species do tend to steal the show however, and the Lesser Whitethroats were particularly popular and also quite relevant to this year’s theme at Birdfair; protecting species in the Eastern Mediterranean. With their easterly migration route, there could be a good chance the Lesser Whitethroats which were ringed could be passing through the Eastern Mediterranean soon.

Lesser Whitethroat taken by Morris Rendall

There was a promising start to the event, when at 8:55 am on the Friday morning, the very first bird in the nets was actually a Sparrowhawk! Unfortunately in this case the bird proved too quick for the ringers and managed to free itself within seconds. So it was an especially pleasant surprise when another adult male Sparrowhawk found its way into the nets on the Sunday morning and even better it already had a ring on. This bird was originally ringed at Rutland Water in 2012 and we now know it is still going strong. A very lucky crowd were able to watch the ringers process the bird.

Adult male Sparrowhawk - Dawn Balmer
Sparrowhawk getting efficiently processed while a lucky crowd watch on - Dawn Balmer
Perhaps the most unexpected bird of the weekend was a House Sparrow (and perhaps a sign of the times since this species has seen a substantial decline in recent years) which is the first ever caught during the Birdfair ringing demonstrations.

Unfortunately, we also had our fair share of unfavourable weather over the weekend so there were times when we were unable to safely catch birds. But nonetheless there were ringers on hand to answer questions and even ‘ring’ some people with the wristbands we had available (if you were ringed you can find out your story here).

The ringing demonstration stand. You can tell where the bird is by the crowd - Stephen McAvoy

It is always a privilege to be able to ring birds and even more so at an event like this. It requires a lot of planning and I would just like to thank all those ringers who volunteered their time to help with the demonstration again for all their hard work, in particular the Rutland Water Ringing Group, as well as everyone who came along to see us.

Eds - There are ringing demonstrations run at various sites across the UK by individual ringers or groups however the BTO, in collaboration with the RSPB, are running their next event on Sunday 30 August at the BTO headquarters from 10 am until 3 pm (catching weather dependent).

07 August 2015

Owl and raptor mid-season update

That annual Barn Owl breeding success is influenced by peaks and troughs in abundance of field voles, the species' main prey item in many areas, is hardly news to Barn Owl recorders. But after seeing some of the lowest levels of nesting activity in memory in 2013, followed by record productivity in 2014, many might be wondering just when they'll next get an 'average' season. Not in 2015 it seems: anecdotal reports so far suggest Barn Owl productivity has been much lower than expected, though other species seem to have followed on better from last year's bumper season.

Poorer than predicted Barn Owl breeding

Back in February, Barn Owl expert Colin Shawyer predicted that, provided spring conditions remained mild, the exceptional number of 2014 fledglings would mean good recruitment of young breeding birds, but also that though egg-laying could be expected at the usual time in late-April/early-May, a decline in vole numbers from their 2014 peak would result in smaller brood sizes and fewer fledglings this year.

Subsequent early visits to Barn Owl nest boxes revealed much less activity than expected. In late May, Colin visited 25 boxes that had contained 16 active nests in March 2014, only to find just eight with signs of adults present and three clutches of eggs. Non-breeding females were found to be underweight, suggesting that, whether caused by recent wet weather affecting foraging or simply the scarcity of voles, birds were late getting into breeding condition.

By mid-June, reports on the NRS Forum were sounding similar. Alan Ball, Bob Sheppard and Keith Bowden, in Lincolnshire, had checked most of their boxes and found four Barn Owl pairs on eggs or chicks. On the same date in 2014, they had been monitoring 200 nests. Frank Mawby, in Cumbria, Peter Wilkinson, in Cambs, and David Garner, in Cambs, were also reporting low breeding occupancy, and an apparent shortage of prey. Bob Danson, a recorder in Lancashire, commented that food larders had disappeared after the very beginning of the season, in contrast to 2014 when piles of six and seven voles were common.

A single Barn Owl chick at 20-25 days. In 2015 there have been many reports of broods sizes dropping to just one or two chicks. Photo by BTO.

In mid to late July, when Barn Owl chicks are often ready for ringing, there were reports of brood sizes of three and four having reduced to just one—Mike McDowall in East Lothian, David Garner in Cambs and Frank Mawby in Cumbria all ringed single chicks. By the time Bob Danson had ringed his latest brood on 3 August, just eight of the 23 nests he had found so far in his 80 boxes had produced chicks, and his ringing total had reached only 18.

Better Barn Owl news has come in from elsewhere: Nigel Lewis at Salisbury Plain observed a good proportion of boxes with clutches of eggs in May and Judith Smith, in Manchester, has ringed several healthy broods of four and five chicks, including some in new boxes. Geoff Myers, in Lancashire, reported that good numbers of both early and later laying Barn Owl pairs had successfully reared broods and that by 24 June he had ringed a brood of six and several broods of five—very advanced compared to elsewhere.

Tawny Owl, Little Owl and Kestrel fortunes

There have been mixed reports for other box-nesting owl and raptor species that tend to be well-monitored by ringers and nest recorders. Alan Ball, Keith Bowden and Bob Sheppard reported that they had ringed just six Tawny Owl chicks in their boxes in Lincolnshire, compared to 130 in the same boxes in 2014. On the other hand, Bob Danson, in Lancashire, encountered 17 nests in 30 boxes—his second best annual total after last year—from which 26 chicks fledged, including four broods of three. Bob noticed that rats made up a higher proportion of prey in his Tawny Owl boxes, along with baby rabbits.

Several recorders have spoken of Little Owls doing well this year, a species that is obviously less dependent on rodent prey. Alan Ball, Keith Bowden and Bob Sheppard monitored 65 nests and ringed 100 chicks, compared to 80 nests and 188 chicks in 2014. Bob Danson's 70 Little Owl boxes saw occupancy increase to 16 pairs in 2014, from 12 in 2014 and 7 in 2013. He recorded 36 fledged young altogether, including a brood of five and two broods of four.

Two recently fledged Kestrels photographed by Wilf Hockney, who accompanied Steve Baines on several of his Kestrel box rounds this year. 

Kestrel reports have also been positive. Steve Baines monitors 20 boxes in Chelmsford, Essex, and 13 had pairs this year, one of his highest occupancy rates, though he noted that clutch sizes were down relative to 2014: clutches of five and four but no sixes, and that the number of chicks fledged overall (36) was slightly lower than 2014. Bob Danson reported a similarly successful season for Kestrels in Lancashire and noted more bird prey in boxes than usual, including a Swallow. In contrast, Alan Ball, Keith Bowden and Bob Sheppard had monitored only 6 nests by mid-June, compared to 150 at the same time in 2014.

Late season comeback?

Although the breeding season has now finished for Tawny Owl and Little Owl—bar perhaps a few exceptionally late nests—there will still be a proportion of Kestrels tending to chicks, and of course there is the question of whether we will see any Barn Owl second broods or late-season nesting attempts in previously empty boxes. As Dave Leech has pointed out in a recent interview for Radio 4, this might happen if non-breeding females have managed to get into breeding condition, although Colin Shawyer has observed that vole numbers appear to remain very low. Either way, good data on the extent of late and repeat broods is essential for assessing Barn Owl productivity, which is why those late-season box checks are so important...

The BTO Nest Record Scheme is one of the ways in which raptor populations are monitored in Britain & Ireland. These results are complemented by periodic single-species surveys and, in Scotland, by the Scottish Raptor Monitoring Scheme.

Many thanks indeed to: Steve Baines, Alan Ball, Keith Bowden, Bob Danson, Wilf Hockney, Nigel Lewis, Frank Mawby, Mike McDowell, Geoff Myers, Colin Shawyer, Bob Sheppard, Judith Smith, Peter Wilkinson