With migration pretty much over (it never truly stops altogether) now is a good time to reflect on what kind of a migration season it has been.
The most obvious feature has been the weather. Migrant birds heading back to the UK from their winter in Africa and southern Europe have had to battle against some horrific conditions. Strong winds, heavy rain, hail and even snow have all featured and less than ideal conditions have dominated pretty much throughout the migration period.
So, what effect has this had on our summer visitors? The first and most obvious effect was to delay the arrival of a number of them, as evidenced by the BirdTrack reporting rates. Whitethroat and Lesser Whitethroat illustrate this well.
Initially it looked like the numbers of many of our summer migrants were going to be quite low this year, and indeed early evidence for Swallow, Swift and House Martin suggest that this might be the case. However, it is interesting to note that Portland Bird Observatory, Dorset have had one of their best springs for numbers of common migrants for many years. At Portland, Whitethroat and Lesser Whitethroat showed an increase of 138% and 137% above the 2007-11 average. The BirdTrack results also indicate that both of these species are at or near their normal levels.
It is too early to know for sure whether there are fewer birds here or not. We will have to wait until later in the year when all of the data that BTO volunteers collect through surveys such as the Breeding Bird Survey, the Constant Effort Ringing Scheme, BirdTrack and the Nest Record Scheme has been analysed to know how out birds coped with a very abnormal spring and early summer.
Anyone can take part in these surveys and help contribute to the bigger picture. For more information, please visit the survey pages on the BTO website.
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