Page 11 - Complete Birds of Britain and Europe (DK - RSPB)

EVOLUTION

NATURAL SELECTION
“Only the fittest survive.” That is the theory of natural selection
and it is true that the birds best adapted to an environment
have an advantage over the rest and produce offspring that
perpetuate their own genetic make-up.There are many
ways in which a species may evolve in response to changing
habitats or food. If such a change happens in only one part
of a species’ range, and the birds in that area remain separate,
they may change so much that they can no longer interbreed.
The result is two species instead of one.There is a halfway
stage: two groups may differ
in size or colour, but can
still interbreed.At this
point they are called
“subspecies”
or “races”.

PERSISTENT STARLING
The common Starling is successful through most of
Europe but does not breed in Iberia and North Africa,
CHAFFINCH
where the Spotless Starling replaces it. This latter species
must have evolved in isolation but has persisted despite
BRAMBLING an influx of common Starlings into Spain every winter.
EVOLUTION THROUGH ISOLATION
Two finches in the family Fringillidae are alike in size, CLASSIFYING BIRDS
shape, pattern, and even in their behaviour and calls. The purpose of classifying birds is to indicate the relationship
The Chaffinch and the Brambling evolved as two between them while at the same time giving each species a
species from one ancestor. The Ice Age forced one unique name.Birds are grouped into “orders”,each with one
population (later the Chaffinch) southwest, the other
(which became the Brambling) southeast. Ice caps on or more “families”.The next subdivision is the “genus”,which
mountains in the centre separated them for millennia. has one or more “species”(denoted by a two-part name).Some
species are split into “subspecies”,indicated by a third name.
EXTINCTION
Aves (Birds) Class

Passeriformes (perching birds) Order

Motacillidae (pipits and wagtails) Family

Extinction is forever: the total
loss of a species from the world. Motacilla Genus
Modern rates of extinction are
exceptionally high and still
accelerating. In Europe, however,
we have lost only one species in Species
historical times: the Great Auk.
This large, flightless relative of the Motacilla alba Motacilla flava Motacilla cineria
Razorbill bred in Scotland but
was hunted until few remained;
the final survivors were killed by
collectors of stuffed birds.The last
pair to be seen alive were then Subspecies
killed off Iceland in 1844.
M. a. alba M. f. flava M. f. feldegg

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