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Recording Year Spring Migration For many birdwatchers, the spring migration period is the most exciting time of the year. It is a time of change, with the departure of winter visitors and arrival of summer migrants. Whether you live on the coast or inland, you will see birds moving. Birdwatchers regularly record the first arrival dates of migrants such as the first Swallow or Cuckoo of the year. These first dates are often ‘extremes’ and don’t give us much information about the main periods of migration. By contributing to BirdTrack you will help build up an annual picture of spring migration and we will be able to monitor the timing of arrival of spring migrants and departure of winter visitors. There is a lot of excellent information collected annually by Bird Observatories. The wardens make complete counts of the birds in a defined area each day and record the results in daily logs. These log books are an incredible resource and have been used by Dick Loxton and Tim Sparks to look at arrival dates over time at four bird observatories: Portland, Skokholm, Bardsey and Calf of Man. The table below shows the average arrival date at each observatory. For some species there was not enough information to produce a meaningful average arrival date. Table 1: Average arrival dates of 24 spring migrants at four bird observatories
However, there are just 18 Bird Observatories dotted around the coastline of Britain and Ireland. With large numbers of birdwatchers spread over a broad geographical area we can find out much more information about the timing and pattern of arrival and departure of migrants in spring. The table below shows the average arrival dates of summer visitors taken from bird reports of five counties spread from southern England to the Shetland Islands. Data is not available for all species from these selected counties but few county bird reports provide average dates at all, most give first and last dates. Look at species like Turtle Dove and Cuckoo and see how the average arrival dates are spread. As we might expect, average arrival in Hampshire is earlier than in the West Midlands and so on. With so many birdwatchers contributing to bird reports its perhaps not too surprising that average arrival dates are often earlier than those collected by bird observatories where just one or two people contribute information from a small area. Table 2: Average arrival dates of summer visitors
na = not available
Table 3: Average departure dates of winter visitors
na = not available References Cox, A. 2003. Hampshire Bird Report 2002. Hampshire Ornithological Society. www.hants.gov.uk/hos Emley, D.W. 2003. The Birds of Staffordshire, Warwickshire, Worcestershire and the West Midlands 2001 Annual Report 68. West Midland Bird Club. www.westmidlandbirdclub.com Loxton, D. & Sparks, T. 1999. Arrival of spring migrants at Portland, Skokholm, Bardsey and Calf of Man. Bardsey Observatory Report 42: 1998. Mackay, A.J. 2002. The Leicestershire and Rutland Bird Report 2001. The Leicestershire and Rutland Ornithological Society. www.lros.org.uk Pennington, M. 2003. Shetland Bird Report 2002. Shetland Bird Club. www.nature.shetland.co.uk/birdclub/ White, S.J. 2003. Lancashire Bird Report 2002. Lancashire & Cheshire Fauna Society No 104. www.lacfs.org.uk
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For
some species the average arrival dates at all four observatories
are very similar eg Willow Warbler, Ring Ouzel which suggests that
these species move quite fast northwards. Other species such as
Turtle Dove seem to move more slowly northwards in the spring, with
20 days between the average arrival dates at Portland and Bardsey.
Generally
speaking there is far less information about the timing of departure
of winter visitors such as thrushes, swans, geese and ducks. Recording
departure dates are more difficult as you need to record every day
until you see the last one. By submitting your records regularly
to BirdTrack we will be able to investigate the timing of departure
for a wide range of species. Migration Watch was able to record
the departure of Redwing, Fieldfare and Brambling and this gave
us a good insight into the timing and pattern of departure. Very
few bird reports provide information of the departure dates of winter
visitors and even fewer are able to present average dates. The table
below gives average departure dates of winter visitors in Hampshire
and West Midlands.
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BirdTrack is organised
by the BTO for the BTO, RSPB and BWI |
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