16 February 2017

You’re in for a tweet, with National Nest Box Week

Hazel Evans (Nest Records secretary) writes:

With flurries of snow and frosty mornings over the weekend just gone it hardly feels as though spring is in the air, however some of our garden birds such as Blackbirds and Collared Doves have already started nesting and now is the time for nest box residents to start looking for a place to raise their young. This week is the BTO and Jacobi Jayne’s National Nest Box Week, which aims to encourage and promote putting up nest boxes in your garden and local area.

Whether you buy a nest box from your local garden centre or build a selection of your own, there is no doubt that putting up a nest box is one of the most valuable things you can do for your garden birds. The BTO’s National Nest Box Week webpage contains lots of information on which nest boxes are suitable, how to build a box and where to place them. You may be surprised by the variety of boxes that are available, from Barn Owl to House Martin and Blue Tit to Starling.

Nuthatch. Photo by Edmund Fellows

If you are looking to do more than putting up a couple of boxes in your own garden, you might consider contacting a local landowner, farmer, the council at a local park, or if your children are enthusiastic, their school might allow a few nest boxes to be put up in the grounds. Once the boxes are securely in place it is time to wait and keep your fingers crossed!

Hopefully you will soon see some activity at the box; birds entering and leaving, pecking the entrance hole and carrying nesting material in. The real conservation value of erecting a box is the opportunity it provides to monitor nesting attempts. As long as the BTO Nest Record Scheme (NRS) Code of Conduct is adhered to, we can safely look inside at intervals to count the number of eggs and chicks and submit this data to the scheme. This provides incredibly valuable data, and is also a rewarding and fascinating thing to do. This information is used by the BTO to study the breeding performance of wild birds to help identify when reduced productivity might be causing population declines. People can be concerned about opening up a nest box and checking the contents, but done in the correct way the value of the data collected is huge.

Each year, data from NRS are analysed and, alongside results from the Constant Effort Sites (CES) ringing scheme, are used to produce a summary of the breeding season. In 2016, the data collected by NRS and CES volunteers showed that whilst there were good numbers of adults at the start of the season, there was a late start to the breeding season for some species and productivity was generally poor. Additional results from NRS are presented in the annual BirdTrends report.

As this is the Demog Blog, I feel that as well as the nest monitoring side of nest boxes, I should also mention the value of ringing these broods. I am currently a trainee ringer and in addition to monitoring the nests in the boxes at BTO HQ and a local farm, I am able to ring all of the chicks (under the supervision of my trainer). This provides a huge amount of data – this year I will be monitoring around 70 nest boxes – and it is also a fantastic learning experience.

A Blue Tit shaking it's Bluti. Photo by Jill Pakenham

The most common inhabitants of our nest boxes are Blue and Great Tits. Combining the data from the thousands of nests monitored every year with the thousands of pulli ringed, provides an invaluable national picture for these species. The amazing coverage provided by BTO volunteers allows BTO scientists to explore how changes in the environment affect breeding birds and how their responses vary between regions and habitats. 

Nest boxes can of course be put up at any time of year but winter is ideal as it provides time for prospecting birds to find the site before the breeding season. Once used, it is a great idea to clean out old nests the following winter to allow for a fresh start in the spring. To comply with legislation, nests can only be cleaned out between 1 September and 31 January.

This year we are celebrating 20 years of National Nest Box week, so please do get involved by putting up a nest box and make your contribution really worthwhile by registering with the Nest Record Scheme

10 February 2017

We're stuck in 2016

Since the end of 2016, the Demography Team has been hard at work loading all the ringing data received from our ringers. Data are still coming in by the 'file load', but here is a sneak peek at a few highlights of 2016.

The big question is always, "how many birds were ringed in 2016?". I don't think we will reach a million birds ringed this year, possibly due to Blue and Great Tit not having a great year. We are currently on 990,808 birds ringed and there is a corresponding 281,880 records of birds already wearing rings (either caught again by ringers or found dead by anyone).

The graph below shows the 20 most ringed species in 2016. Despite them having a poor year, Blue Tit is still by far the most ringed species but perhaps more interestingly, Goldfinch is in second place. BirdTrends records show that Goldfinch numbers have increased substantially in recent years; however it is only the 10th most recaught species.

Top 20 species of birds ringed in 2016. Click to enlarge.

Unlike Willow Warbler, Chiffchaff has been doing very well recently, and as you can see from the graph, was the fourth most ringed bird in 2016. The preliminary results from the CES scheme show that Chiffchaff had the highest adult abundance in the history of the scheme last year. Unfortunately, productivity was significantly down in 2016 and the Nest Record Scheme results show that the mean laying date was eight days later than average. Chiffchaff that had originally been ringed in the Channel Islands, Germany, Spain, France, The Netherlands and Portugal were found in Britain and Ireland in 2016. All, apart from three birds were caught by our BTO ringers, one was found dead and two hit a window (one survived and one didn't).

A young Chiffchaff. Photo taken by Lee Barber
Coming in at number five of the most ringed bird for 2016 was Blackcap. This bird also had a high adult abundance and an even lower productivity than Chiffchaff  in the preliminary CES results. The North Wilts RG ringed an impressive 2,209 Blackcap in 2016, and their ringing session on 11 September, where they caught 257 Blackcap (most of which would have been on autumn passage), will always be remembered by the team on that day.

Male Blackcap. Photo taken by John Dunn.
Some of the more unusual recoveries we received in 2016 include a Blackcap which was found in a 'Horse water bucket', ringed by the West Wilts RG in 2011. We occasionally get birds being hit by vehicles, however I have never heard before of one which was 'trapped inside locked vehicle (entered through partly open window), fresh dead'. We also received a report of the fourth Slovenian ringed Blackcap found by a non-ringer. There are still a few records to be processed of BTO-ringed Blackcap that were found abroad and we look forward to processing those and letting the ringers know if it is one of theirs.

All of the recoveries of fresh dead birds and recaptures of live birds, feed into the longevity records for Britain and Ireland. It will be a little while until the 2016 records are added, but there are a couple of records that look to update the current longevities. The Bisham Barn Owl Group look to have just pipped the current record by a few days, originally set in 2012 (of 15 years 3 months). Click here for more information. The Mediterranean Gull record currently stand at 15 years 3 months as well, and Allan Hale has reported two colour ringed Med Gulls at Great Yarmouth beach, which were ringed just two days apart breaking the current record by over three months.

This post covers just covers the tip of a very big 'data' iceburg, so as we have more time to look into this data, we will undoubtably uncover more exciting information.

02 February 2017

Where do our wintering Blackcaps come from and why?

Over the next three winters, a new study focusing on Blackcaps wintering in Britain and Ireland will help reveal how novel migratory changes arise and spread.  The study will look at genetic and morphological differences between breeding populations and migration strategies, as well as investigate aspects of wintering behaviour, movements and survival of individuals wintering in Britain.

Up until 50 years ago, wintering by Blackcaps in Britain & Ireland was quite unusual, but numbers have since increased considerably, with many thousands now counted each winter by BTO Garden BirdWatch. Gardens are favoured sites where a combination of ‘natural’ berries and fruit along with specially provided fat, seeds, cake and pastry is the main attraction, often fiercely defended by some individuals. 

Male Blackcap. Photo by Greg Conway.

Typically, the majority of Blackcaps breeding in northern Europe migrate to the Mediterranean region for the winter. However, this is changing – some of these birds may now be migrating in a north-westerly direction to the British Isles instead! These changes appear to be facilitated by milder winters and the abundance of food provided by people, according to research carried out using Garden BirdWatch data.

A number of studies have suggested that our wintering birds come from central Europe (southern Germany/Austria), but the small number of ringing recoveries available (see map below) indicates that many may originate much closer to home, or even be resident!  Unfortunately, few recoveries confirm movements between the breeding and winter season.

Origins of ringed Blackcaps wintering in Britain and Ireland and their locations from the breeding season (red), autumn (blue) and spring (grey) (Migration Atlas – Wernham et al 2002).

To improve our knowledge of migration and breeding origin, a number of wintering Blackcaps have been fitted with Geolocators (accurate to around 70km).  These will reveal where they spend the summer, but only once re-caught back at their wintering sites.

Female Blackcap fitted with a geolocator. Photo by Greg Conway.

Colour ringing allows individuals to be identified with unique combinations and this will be used to learn more about winter behaviour, movements and use of wintering sites in Britain, which is surprisingly little understood.  Some appear to remain in the same garden all winter, but others do not!

Male Blackcap with unique colour rings. Photo by Greg Conway.

We would be very grateful for your help with the following:
Blackcap sightings - If you have wintering Blackcap in your garden please let us know and report your counts using BirdTrack or consider joining Garden BirdWatch.

Colour ring sightings - Please report all observations to: blackcap@bto.org

Ringers – Help with catching and colour ringing more Blackcaps over the coming winters would be much appreciated.  If you don’t have sites with Blackcap we can provide details of local sites where ringing is required.

To find out more about getting involved please contact: blackcap@bto.org

Greg Conway (BTO) & Benjamin Van Doren (Oxford University)
This study is collaboration between Oxford University, BTO, Exeter University and the Max Planck Institute for Evolutionary Biology, Germany.