A brief analysis of Grasshopper Warblers ringed at Lytchett Bay 2004 - 2013

Ringing has occurred every summer in the reed beds around the north-west shore of Lytchett Bay since 2004.

Grasshopper Warbler is an uncommon migrant and rare summer visitor to Dorset. However its perceived occurrence on autumn migration is strongly influenced by a combination of its habitat choice and unobtrusive behaviour. It is generally silent and remains hidden in dense vegetation or long grass.

126 Grasshopper Warblers were ringed between 20^th July and 2^nd October during the ten year period. In the same period there have only been 5 field sightings.

The annual distribution is shown in Fig 1

 Over the period the ringing method has remained largely unchanged, though the number and location of nets have varied to a small degree. The song of Grasshopper Warbler is played via a cassette and speakers, on a mixed tape with Aquatic Warbler song, from 45 minutes before dawn until 08:00.

Ringing was undertaken on 134 dates between 20^th July and 31^st August over 10 years, the peak migration period for Grasshopper Warblers. At least one bird this species was ringed on 54 dates (40.3%). In addition ringing occurred on 33 occasions in September. At least one bird was ringed on 7 dates (21.2%). 1 Grasshopper Warbler was caught in Oct, on the 2^nd in 2010.

The pattern of occurrence between the 20^th July and 4^th October is shown in Fig 2

Only one of the Grasshopper Warblers ringed at Lytchett Bay has been recovered. A first year bird ringed on 29^th Aug 2007 was taken by a cat 47 days later in Staplehurst, Kent on 15^th October. A surprisingly late date for a bird of this species to be in Britain.

Typical of migrant passerines ringed in autumn, the majority of birds trapped were first years. Only 7 (5.5%) were adults.

Birds move on from the area quickly. Only 2 birds have been recaptured on a subsequent date following ringing.

Shaun Robson

October 2013