Nature Notes - September 2011
The end of August and throughout September is the peak of the autumn bird migration with many of our summer species heading south to avoid the rigours of the northern winter. However what is generally not known is that autumn for some birds starts much earlier with departures in July. A good example is the swift which, by the first week of August has usually left its breeding haunts and gone. Birds seen along the south coast after this are generally migrants from further afield.
Another bird that departs early is that well known and easily recognized semi villain of the birding world, the cuckoo. Any birds seen now will be juveniles, raised by unsuspecting parents such as meadow pipits and reed warblers.
This year the early departure has been amply demonstrated by some research being undertaken by the British Trust for Ornithology, the BTO: the cuckoo has, sadly, declined rapidly over the last 25 years with the reasons for this being unclear but basic information on wintering areas and migration routes is lacking.
Therefore this year the BTO have fitted 5 cuckoos with minute 5g satellite tags such that they can be tracked on leaving the UK. The five birds were all caught close to each other in east Anglia and had all departed from the UK by the third week of July; indeed four of the birds left in June.
The birds have been tracked through Europe and are now all in Africa with four south of the Sahara in the Sahel and one in Morocco. Amazingly, they have taken different routes through Europe and are currently separated by up to 3600km despite being caught within 70km of each other!! To review their migration routes and follow their progress, go to http://www.bto.org/science/migration/tracking-studies/cuckoo-tracking
Similar to the Osprey project already discussed in Nature Notes, hopefully their wintering behaviour can be monitored and the onset of their return journey recorded. For those interested, the BTO also have a similar project looking at nightingales which can be viewed on a link on the same site.
What to look for in September
Pipistrelle Bat
Pipistrelle Bat
As well as the birds migrating, it can also be a good time to see immigrant moths and butterflies with clouded yellow being the most likely of the latter although large influxes of painted lady and red admiral can take place at this time.
Common blue butterflies and gatekeepers are still around and if you visit a chalky area further east such as Portland or the Dorset/Wiltshire chalk downs look for the striking Adonis blue.
Bats are quite in evidence early evening with the small pipistrelle being the most obvious; these little creatures are capable of devouring 3,000 insects in just one night.
First Published September 2011 By The Dart