Sunday, 18 August 2013

Titchfield Haven - Bird Ringing Second Update August 2013

Bird ringing at the Haven was restricted to the Saturday only this weekend since it was forecast to be very breezy on Sunday. At 5 am it was flat calm, not a breath of wind, and before long it was evident that there had been a good movement of birds. Grasshopper warblers were the first species caught, but as seems to be the pattern this year they were not present in particularly high numbers, only seven new birds were ringed. By contrast sedge warblers have been abundant this year, and that pattern continued, with 106 new birds ringed. Reed warblers also were in good numbers with 54 new birds ringed, but the surprises came in the form of garden warblers and common redstarts. 

First Winter male Common Redstart

I have previously written about common redstarts since it is a species that we don't catch very often, in fact one or two a year is a good result. On Saturday two first year male birds were trapped and ringed within the first hour, our first two of the year. 

First Winter male Common Redstart

Male birds are very obvious since they exhibit a dark throat, evidence of a white eyebrow and a grey mantle, as can be seen in the image above. The bigger surprise was the numbers of garden warblers. This is a species that we will typically catch around 100 birds a year, and on a good day will catch 10 new birds. This weekend we caught 24 new birds in one morning, which was astonishing. The total included two adult birds but the rest were juveniles. 

By the end of the session we had ringed 217 new birds, so not as many as the previous weekend but a good haul all the same. The total included 106 sedge warblers, 54 reed warblers, 24 garden warblers, nine willow warblers, seven grasshopper warblers and six common whitethroats.

Looking at the numbers I was intrigued to see how this year compared to the last few years, since 2011 had been exceptional for many species whereas 2012 had been a dreadful. Below is a graph and table giving the ringing totals at the haven between the start of each season between 2010 and 2013 to 23rd August 2010 and 17th August 2011 - 2013 . To ensure that the analysis was comparable I compared the same dates where I could, although it was not possible for 2010. I hope you will agree that it makes interesting reading.

Comparison of Ringing Totals between 2010 and 2013 at Titchfield Haven

The numbers of sedge warblers ringed this year are on a par with the record year of 2011, and reed warbler numbers are in fact higher. Presumably this indicates that both these species have had good breeding seasons. Willow warbler numbers are higher than 2012, but the overall trend for the last four years is still down and grasshopper warbler numbers are on a par with 2010, which was the last average year. Garden warbler numbers are slightly up, albeit boosted by the record day on Saturday, and blackcap numbers mirror those of 2010. Common whitethroat numbers have not recovered from the 2012 low, but Cetti's warblers seem to have had an excellent breeding season.

Table of Ringing Totals between 2010 and 2013

So what does all this mean? Well it is difficult to really say at this point in the season, since it may be just that birds are still breeding due to the good weather. Last year we recorded a higher percentage of adult birds than normal at this time, indicating that birds had given up breeding and started to migrate south. This year the number of adult birds recorded for most species has been low, for example grasshopper warbler only two so far and only two out of 24 garden warblers on Saturday were adults. I will do this analysis again at the end of the season so it will be interesting to see how things pan out then.

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