A Mediterranean beach

Allan Hale writes:
"I have been reading Mediterranean Gull rings on the beach at Great Yarmouth since 1999. Of late a group of us have been taking the project much more seriously and we try to make a monthly visit during the period from late summer until the end of winter.

Since the 2009-10 winter we have identified 58 different Mediterranean Gulls that were ringed in 10 different countries.  They have originated from Belgium (32), Germany (12), France (3), Poland (3), U.K. (2), The Netherlands (2), Denmark (1), Czech Republic (1), Hungary (1) and Serbia (1).  There have been multiple sightings of many of these gulls.  Many valuable life histories have been identified, with some of the birds mentioned above also visiting Spain, Portugal and The Azores.

Mediterranean Gull - Dawn Balmer

Mediterranean Gulls have been shown to reach a ripe old age. Three of the birds we have seen this winter were originally ringed in 2001, one of them already 3 years old when ringed. We are anxiously looking out for another which was ringed back in 1999 and last seen at Great Yarmouth during late 2012.

Reading colour-rings has been a rewarding experience. Many onlookers have shown an interest in what we have been doing and have been amazed at the results."

Lee Barber writes:
"Even with all the data collected of colour ringed birds, there are still quite a few unringed birds that visit the site, that we know nothing about. Allan decided to take this project to another level and with the help of Jez Blackburn and his Cannon Netting skills and the kind permission of Seafront Enforcement and Facilities Officer, Keith Eglington, an attempt to catch and ring some of the unringed birds and to collect biometric data on the ones that already have rings was organised.

Now a scarce regular breeding bird, about 20 chicks are ringed every year and the annual total for adult Med Gulls for the last nine years vary from none to eight. These birds can be very wary to anything unusual but hopes were high for a catch, even if it was just one bird (see online report).

Canon net firing - David Pelling

After a couple of canon net fires and 15 unringed and 3 ringed in Belgium Med Gulls were safe under the net, with a few Black-headed Gulls. They were then metal and colour ringed, aged, weighed and measured and then released. We were lucky to have a reasonably large catch and we were able to compare the different ages of birds (below). The second year bird has a light orange beak but more importantly has black wing tips.

Mediterranean Gull. First year bird left, second year bird middle, adult right - David Pelling

 
Hopefully as the winter goes on, more gulls will be ringed and add to our knowledge of the survival and movements of this species. Some birds visiting Great Yarmouth have been seen more than 200 times so the life histories of these birds is fascinating.

Wintering Sand Martins benefit from fewer conspecifics

The theme of this Blog (Demography - "The study of the characteristics of populations, such as size, growth, density, distribution, and vital statistics") certainly applies to David Norman’s long-running study of Sand Martins breeding in mid-Cheshire. In more than 200 mist-netting sessions over 23 years (1981-2003), he ringed 6,053 adult Sand Martins and recaptured 1,179 of them in a subsequent year, many of them multiple times for a total of over 10,000 handlings of adult birds.

Mist netting - David Norman

This long run of data with large sample sizes, and annual assessments of the breeding population from counting nest-holes, allowed a detailed analysis, jointly with Will Peach, which has recently been published in Ibis. The details are in the paper (click here for a copy or e-mail david@davidnorman.org.uk) but in outline the work shows …

1. The annual survival of adult Sand Martins averages around 35%, varying from as low as 10% to a high over 60%, mostly determined by the rainfall in their Sahel wintering quarters. There are fewer insects in the dry years and more birds starve. This is already well-known for several trans-Saharan migrants but this study also showed that the effect is non-linear: above a certain level of African rainfall the birds’ survival flattens off, limited by mortality elsewhere in the life cycle.

2. In this study, there was no effect of summer weather (temperature or rainfall) on adult survival.

3. The size of the breeding population is mostly determined by the survival and return of adults, and much less by recruitment of new birds (one-year-old first-time breeders and immigrants from elsewhere).

Sand Martin - Lawrence G Baxter

 4.  This is the first study to show that overwinter survival in the Sahelian winter quarters is density-dependent. Thus, if the population is high, there is more competition for insect food and more Sand Martins die; if the population is low, even in a dry year there is more food to go round and more martins survive and return to the breeding grounds. 'Population' here means the winter population of all western European Sand Martins, which mix in the Sahel during winter.

5. The recruitment rate of first-time breeding adults was also density-dependent. More un ringed ‘new’ adults were captured during summers when local colony size in Cheshire was relatively small, and vice versa. Competition amongst breeding pairs for nesting sites or food might have caused this pattern.

Sand Martin - John Harding

David and Will comment that such density dependence was suspected from previous studies on other species but required a vast amount of fieldwork and statistical analysis to prove it. Such competition for insect prey may apply to other insectivorous migrants that rely on the seasonal flooding of wetlands across the Sahel zone. Better rains in recent years have allowed breeding populations of several Sahel-dependent species to increase in recent years, but the threat of drought continues to hang over the people and the wildlife of the region.

Thanks to David Norman for letting us know.

Black and Gold

Every BTO ringer who has a current ringing licence has a permit number. Trainee ringers have a permit number of 0000 to start with but when they are able to operate with 'remote supervision' (C permit holder) they get issued with another number . This number then stays with them for the rest of their ringing career. The latest permit number to be issued is currently 5866.

Coming from someone whose ringing permit number is after 5000, seeing data going to ringers with permit numbers below 1000 or even 100 is amazing. After Tony Mainwood qualified for his A permit with number 903, the first bird he ringed was a Blackbird on 31st January 1962. Exactly 50 years on, during a routine ringing session on 31st January 2012 he reached this 50 year 'mile stone' by ringing another Blackbird.


We have 64,249 electronic ringing records for Tony (not including all the ringing he has done with other groups). As he started ringing way before the computerisation of ringing records, his total is actually much much more.

Thanks to Jez Blackburn for the photo.

Waiting for the kids to leave home

Over 36,000 Reed Warblers were ringed in the UK during 2010, so what was interesting about the seven caught at a site in south Norfolk on Thursday?

During the summer of 2011, a team of BTO staff, collectively known as The Swamp Things (AKA Dave Leech, Lee Barber, Rachael Portnall, Mike Toms and Jez Blackburn), decided that the best way to spend their free time would be to slip into a pair chest waders and wander the reedbeds of Norfolk. Why, you ask? A good question, especially when the temperature rises into the high twenties and the horseflies are hungry, but there was method in their madness as there really is no other way to collect data on the nesting success of Reed Warblers.

So, when the warblers arrived back from Africa in April, The Swamp Things sprang into action, catching and ringing the adults, finding their nests and ringing the chicks. The first full clutch of eggs was recorded on the 8th May, and the last nestling was ringed on the 12th August, by which time several of the team were looking considerably sleeker and, at least from the shoulders up, more tanned. In the intervening three months, they monitored 257 nests and ringed 596 nestlings. An added bonus was provided by the 12 nests parasitized by Cuckoos, of which at least seven were thought to have fledged (and by now have presumably joined Clement , Martin, Caspar, Lyster, and Chris on their wintering grounds).

The seven birds mentioned at the top of this posting were all ringed as chicks in the nest between the 8th and the 30th July and are still finishing their moult and building up their fat reserves. By adding this information to the other recaptures of ringed nestlings, the team will be able to learn a lot more about the behaviour of the youngsters when they reach independence and prepare for their first ever migration, an incredibly important, yet seldom studied, period in their lives.

Thanks to Dave Leech for this post.

Sand Martin Shenanigans

Richard du Feu is currently taking part in a Retrapping Adults for Survival (RAS) study on Sand Martins at Whittington, Lancashire. Little did he expect that one of the breeding males L334091, ringed at the site on 08/07/2010, would be later re-caught by ringers, whilst wintering in Africa, at Parc National du Djoudj, Senegal on 13/12/2010 (4363km in 158 days).

Amazingly he retrapped this same bird, on Tuesday night, at the original breeding site, just 15 metres from where he ringed it last year.


Richard also had two French ringed Sand Martins so far this year and two British controls with several birds moving up to 15km along the river lune. Higher than average numbers of adults have returned to many colonies this summer so the prospects for a productive breeding season are looking good.

Thanks to Richard for letting us know and to Jez Blackburn for the photo.

Incestuous pairing amongst Wood Warblers

Jerry Lewis writes:
I have been monitoring Wood Warbler nests in Larch plantations (Wentwood Forest, Gwent) for about 10 years, and densities are quite good at about 10 pairs per sq km. I ring most of the chicks so when I catch an adult I can usually see how the chicks have dispersed from the natal nest to the breeding site (males move further than females on average). Last month I caught a pair at one site which turned out to be siblings from a nest about 1400m away in 2009. I suppose that although this may not be particularly unusual, it is not often recorded. It was also interesting that 4 of the 6 eggs did not hatch (I seldom record unhatched eggs in nests), perhaps indicative of the "poor" pairing, and unfortunately the chicks were subsequently taken by a predator when about 10 days old.


Lee Barber adds:
Our ringers have ringed about 20,000 Wood Warblers so far and only 47 had been recovered by the end of 2008. The majority of the reports we receive about this species are from ringers doing this kind of valuable work but we have also received a few reports of birds found abroad. All of these were of dead birds and were from Italy (8), Morocco (1) and Algeria (1). We have had no foreign ringed birds being found or caught in this country yet.

Posted on behalf of Jerry Lewis and photo by Jez Blackburn