Wednesday, 27 August 2014

A History of Grasshopper Warblers at Titchfield Haven

Bird ringing studies began at Titchfield Haven in 1973 and in those days the Grasshopper Warbler Locustella naevia was a regular breeder at the site. Between 1973 and 1998 the species was one that was only occasionally caught with 18 birds ringed, the totals are as follows; 1 in 1973, 1 in 1974, 1 in 1979, 1 in 1981, 1 in 1986, 1 in 1990, 8 in 1992 and 4 in 1994. In 1999, the year after I began ringing at the Haven, we decided to try and target Grasshopper Warblers in order to understand more about the migration of the species.

Juvenile Grasshopper Warbler - Titchfield Haven 2014

We sought advice from Trevor Squire, who in those days was the lead ringer at the Icklesham site in East Sussex, as they were catching good numbers annually, and set about our task. We set our nets low to the ground and used tape lures of a singing male Grasshopper Warbler. These were set to come on 1.5 hours before sunrise, as British Trust for Ornithology  guidelines recommend. In our first year we caught 31 birds and were pretty chuffed with our results, but had no idea how the numbers would increase in the future. 

In Birds of Hampshire (Published by the Hampshire Ornithological Society in 1993) Grasshopper Warbler was described as "A scarce summer visitor which has declined considerably since 1970". Cumulative totals of singing males between 1966 and 1990 showed a decline from 139 to 52, so the species was evidently undergoing a dramatic decline in Hampshire. Today the breeding status of Grasshopper Warbler in Hampshire is hanging by a thread with only 12 singing males recorded in 2012 (2013 and 2014 figures are not yet available). 

Despite the decline in breeding numbers, the autumn totals at Titchfield Haven increased from the 31 in 1999 to an annual average of 281 birds. The peak was an exceptional total of 950 birds ringed in 2011, which was also a record year for many species. The total number of birds ringed at the Haven from 1999 to 24th August 2014 stands at 4502, with the grand total standing at 4523.

One of the most interesting facts that we have learnt is the numbers of birds that pass over the Haven during the autumn migration. It is also interesting to note that the first birds are recorded during the second week in July, and can be recorded up to the second week in October, albeit in much smaller numbers. The peak migration period for the species are the last two weeks of August, although there is an initial peak during the last two weeks of July and good numbers are still recorded during the first two weeks in September.

So what else have we learnt? Unfortunately there are not many sites other than the Haven and Icklesham that are ringing Grasshopper Warblers and that is reflected in the number of recoveries and controls that we have had (see below). The hope is that more ringers will try and ring pulli and adults on their breeding grounds so that we could gain a better understanding of where the birds that pass through the Haven come from and are going to. To date we have only had two foreign recoveries, one from France and one from Senegal.

Recoveries and Controls
Y096313             N     3J                      24/07/11          Wheldrake Ings Nature Reserve, Wheldrake, York
                         C      3    Recaptured  14/08/11  IRP   Titchfield Haven National Nature Reserve (SUFF), Hampshire (341
                                                                                km, S, 21 days)
R586576             N      3                       21/08/05  TDC    Titchfield Haven National Nature Reserve (SUFF), Hampshire
                         C      4    Recaptured  25/01/07          Parc National du Djoudj, Fleuve, Senegal, Senegal (4054 km, SSW,
                                                                                1 yr 157days)
R586596           N      3                       23/08/05  BSD   Titchfield Haven National Nature Reserve (SUFF), Hampshire
                         X      0    Dead           30/06/08          Enstone, Oxfordshire (127 km, N, 2 yrs 312days)
T098831            N      3                       17/09/06  BSD   Titchfield Haven National Nature Reserve (SUFF), Hampshire
                         X      0    Long dead   19/02/07          Selbourne, Hampshire (36 km, NE, 155 days)
T617642            N      3                       02/08/08  BSD   Titchfield Haven National Nature Reserve (SUFF), Hampshire
                         C      4    Recaptured  27/06/10          Ailsworth Heath, nr Peterborough (207 km, NNE, 1 yr 329days)
V680118           N      3                       29/08/09  TDC    Titchfield Haven National Nature Reserve (SUFF), Hampshire
                         C      4    Recaptured  15/05/10          Hasfield Ham, Gloucestershire (142 km, NNW, 259 days)
V680191           N      3                       05/09/09  TDC    Titchfield Haven National Nature Reserve (SUFF), Hampshire
                         C      3    Recaptured  11/09/09          Villeton, Lot-et-Garonne, France (727 km, S, 6 days)
Y457414           N      3                       15/09/12  DAB   Titchfield Haven National Nature Reserve (SUFF), Hampshire
                         C      4    Recaptured  12/04/14          Bicester, Oxfordshire (113 km, N, 1 yr 209days)

1 comment:

  1. I just noticed earlier today that the West Cornwall Ringing Group posted good numbers of Grasshopper Warblers on their blog :



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