Guest blog by Allan Smith, Waveney Bird Club Ringing Group
The Waveney Bird Club have been ringing Minsmere's sand martins for the last two years, with the first ringing session of 2015 recently undertaken.
Sand martins feed on small aerial insects throughout the year. They are summer visitors in the UK, where they seek out low sandy cliffs for nesting. The sand cliff close to the Minsmere visitor centre is ideal for a colony. The nest chambers are formed by the bird burrowing into the vertical earth and sand face. These holes can be up to one metre long, where 4 – 5 eggs are laid. Incubation is 14 – 15 days, with fledging being a further 19 – 21 days after hatching.
European sand martins migrate to spend the winter in the Sahel region of Africa, which is an area just south of the Sahara desert, an important wintering habitat for many European migrant song birds.
A total of 105 sand martins were recorded at this session. Birds caught for the first time have an official BTO ring placed on one leg. These rings have a unique individual number on them which is specific to each bird. It is this unique number which enables the ringing group, in conjunction with the BTO database, to record and monitor all information about the birds if they are re-caught or found dead. As well as ringing each bird, various measurements and other data are taken, including age, sex, wing length, weight, and readings that allow us to calculate how much fat and muscle they have. All of this information is provided to the BTO using an online computer programme known as IPMR.
It is extremely rewarding to discover that, of the 105 birds caught this year, 12 of them were ringed by our group for the first time at Minsmere in 2014. It is remarkable that these birds, each with an average weight of 14 grams (about the same as two 10 pence coins), have travelled in excess of 4000 miles to their wintering home and back to Minsmere since we ringed them.
Also among this year's catch we ringed 30 juveniles - birds born this year that had only been flying for a matter of days.
The highlight has to be a sand martin with a Paris, France leg ring. ( photo above ) Further details about the history of this bird will follow when the information has been returned via the BTO and the French ringing authority.
The Waveney Bird Club's ringing demonstrations will run every Thursday during the summer holidays, starting next week - Thursday 23 July. The demonstrations run from 10 am to 4 pm, subject to favourable weather conditions, and you can pop along at any time. The event is free, but usual reserve fees apply for non members. We'd love to see you and show you we ring birds.