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Out
of Africa
Investigating the declines of
our migrant birds |
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| Our
summer migrant birds face incredible challenges in their daily
lives but none more so than their annual journeys to and from
Africa. To escape the British winter, migrant birds fly thousands
of miles to reach warmer climates, returning again in spring.
However numbers of our summer migrants, such as the Cuckoo and
Turtle Dove, are declining and we don't know why. |
Read
about the projects |
| How
you can help |
| Watch
clips on the A2B Arrival Calendar |
| Swiftly
disappearing
The arrival of the Swift, reminding us of sweltering
summer days, is always a delight. Shooting through our streets
and screaming across the sky, around and over our houses,
they really do signify that summer is really here. Unfortunately
there seem to fewer in our skies year after year. |
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| On
early morning walks though cool oak woodland two other summer
characters are harder to find. Where's the descending trill
of the Wood Warbler and the distinctive song of the Pied Flycatcher?
These
are not the only changes that birdwatchers are noticing; about
two thirds of all our African migrant species seem to be declining.
The Cuckoo and Turtle Dove have now joined other migrants,
like the Wood Warbler, as red on the List of Species of Conservation
Concern.
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Changes between 1994 and 2007(BBS results) |
| Where
are our summer migrants?
It is hard to
know what is happening to our birds to cause these drops in
numbers, but
it looks likely that habitat change in
Africa (south of the Sahara), caused by changes in land use
and land degradation, could play a part. Migrant birds could
also be facing hardships on their journeys to and from Africa
and in the UK.
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Further research
is crucial; without knowing what is causing the declines,
how can anything be done to stop them? We have to act now
because time is running out. Wood Warbler numbers have dropped
by 60% in just 15 years.
The Out of Africa
appeal will fund a range of projects in Africa, where our
migrants spend the winter, others involving the analysis of
data collected by volunteers in the UK and international collaborations
that focus on the migratory journeys. |
A2B—Africa to Britain
A)
Knowledge gaps about wintering grounds
Our knowledge of ecology of migrants in their wintering
grounds is extremely poor and severely hampers our ability
to explain declines and our ability to conserve this group
of species. We lack even basic information about when
birds arrive, the habitats they use and how they move
around within Africa. Could learning more in Africa help
us explain what is happening? |
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There are striking
differences in trends for those migrants wintering in
different areas.Those closer to the Sahara are increasing
whilst those wintering further south in the rainforests,
are generally declining. This could indicate that there
is a problem in Africa which is affecting migrant bird
populations.
Diagram left shows results from BBS (1994-2007) and
the difference in trends for Top Row A) Sand Martin
B) Reed WArbler C) Whitethroat D) Chiffchaff and bottom
row E) Nightingale F) Wood Warbler G) Spotted Flycatcher
and H) Garden Warbler
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2)
Changing habitats could be having an effect
Habitat in Africa is changing; overgrazing, intensive farming
and the consequent degradation of habitat is altering the landscape
in areas where we believe migrants winter and stop over. Is
this habitat change affecting how much food is available? This
is of huge importance both during winter and as they fatten
up before starting on their epic journeys back to the UK.
If birds can’t gain enough fat to fuel them for their
journeys they may well not make it back to the UK or will arrive
in poor condition and delay their breeding attempts. One of
the new projects involves tracking Nightingales; once they arrive
back this spring and are re-caught, we will be able to download
their flight plans and identify the ‘service stations’
they have used whilst on their travels.
Map right shows Spotted Flycatcher migration
map from 'Time to Fly' by Jim Flegg |
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B)
Nesting problems in the UK
Choosing a time to nest is very important. Resident
British birds which winter in the UK have a head start
on those that spend the winter elsewhere, as they are
able to judge more easily when the warmer weather starts.
This judgement is vitally important because, as soon
as spring arrives, buds open on plants and trees and
insects will start to feed. Birds need to match the
rearing of their chicks with the time when insects are
readily available.
Migrant birds in Africa must try to judge what the weather
is doing back in Britain and time their arrival to coincide
with the beginning of spring and the wealth of food
- no easy feat! |
| Some
birds are nesting earlier. For the Cuckoo early nesting
of its various hosts species, some of which remained in
Britain over the winter, could be a real problem as egg
laying needs to be in synchrony with these breeding attempts.
If host species nest early and the Cuckoo has not yet
completed its journey back from Africa it will miss its
chance to plant an egg in the unsuspecting host’s
nest. |
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| With traditional
nesting sites disappearing, could some species like the
Swift and Swallow, be finding it harder to find suitable
spots for their breeding attempts? Data collected here
in the UK by volunteers in the BTO Nest Record
Scheme and the Ringing Scheme
may well give us some clues about whether nesting is taking
place earlier, and assess the relative sucess of breeding
attempts, in an effort to understand what is happening
to these birds in the UK. |
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See BTO Scientists and media
personalities including Chris Packham, Miranda Krestovnikoff
and Stephen Moss talking about their favourite migrants on the
A2B Arrival Calendar. |
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