A little about Bird Migration

Geese gathering at Alrø bird reserve

The migratory birds move thousands of kilometres each spring and autumn, in spring to the north to their breeding places in Scandinavia in order to nest and have kids. Here is a lot of space and food in summer. In autum the migratory birds fly south to their winter-quarter in the warm countries, where they can rest and find food while snow and frost cover the earth in Scandinavia.

Denmark is a crossroad for both water birds and land birds Birdwatchers estimate that about half a a billion birds pass the southern Scandinavia each autumn.

The land birds prefer to fly over land as far as possible before the flight across sea - therefore they follow the coastline until they are forced to cross the sea.
The water birds prefer to fly across water as far as possible -  therefore they also follow the coast line  until they are forced to fly over land.

An extreme example of bird migration is the Arctic tern which breeds far north near Arctis and overwinters at Antarctis. The species fly usually a yearly migration of ab. 34.000 kilometer. Some individuals can even traverse over 80.000 kilometer yearly, which is the double of the circumference of the earth.

The birds' orientation, the ability to find their way, is genetically determined. How the birds orient themselves is not quite clarified, but it is known that birds use several methods like the Terrestrial magnetic field, constellations, the sun and moon position, polarized light and visual Memory.

Some examinations have shown that the birds not only feed on their fat-reserves but that some of their organs grow smaller during the migration - so the birds exploit the bound energy from fx muscles, stomach, liver and other inner organs. In this way the birds get both energy and a lower weight, which makes the flight easier.

During the migration the birds feed on metabolic water, which is released as a biproduct during the metabolism when the stored fat is burned. The biggest loss of fluid during the flight happens via the exhaled air,  but the birds lose only little fluid through their droppings.

Most of the big birds, like swans and geese, must be taught by their parents in order to find the right migratory route between the winter quarter and the breeding place.

Several migratory birds can fly at least a week in a row without landing.

Some species, like geese and swans, fly in formation during the migration like the V-formation (the wedge formation). A common misunderstanding is that a formation like this has a leading goose in front,  but the birds change place alternately.

It is relatively easy to imagine that a big bird of prey can hover all the way to southern Europe or Africa on spread wings, but it is difficult to imagine a little bird on such a long trip. A bird weighing 10-15 gram has to bring fat in order to be able to survive the tour over long stretches, where it might have no possibility to seek food, water or shadow.

And what I have found here above is just a small part about this fantastic bird migration, the source is wikipedia, the photos; grethe bachmann . 


The bird migration is a wonderful miracle, isn't it? 

Red Kite /Rød Glente

Milvus milvus

Red kite
photo: stig bachmann nielsen 2009 naturplan foto

The red kite is a strikingly beautiful bird of prey with its long forked tail twisting as it changes direction, its long wings with contrasts and its rust-red colour. It is 60-66 cm long with a 175-195 cm wingspan; males have a weight of 800-1000 g, and females 1000-1300 g. It is a fantastic flyer and while looking for food it flies rather close to the ground to check up a possible prey. When it wants to mark its nest-territory it may hang for hours like a kite above the forest - hence its English name kite.

The red kite has contrary to its close relative, the black kite, a limited geographic spread. Almost the whole breeding area of this species is inside Europe. 80% of the European population of red kite is concentrated in 3 countries: Germany, France and Spain. The red kite is declining in all three countries. It breeds in few numbers in Denmark, but it has made progress during the latest years and is now found in all parts of the country. Most breeding couples are in the East Jutland.
Red kite
photo: stig bachmann nielsen 2009 naturplan foto

The red kite breeds in open landsccapes with spread forests, likely near water streams, lakes or moors. It often takes over the nests of other large birds in high trees, like raven- or buzzard-nests. The nest is often decorated with paper pieces, coloured plast, rope etc.

The red kite is also few in numbers as a migrating bird in Denmark, although the numbers of migrating kites in eastern Denmark has been rising, in line with the rise of the south Swedish kite-population. During one autumn season were counted up to 1.000 migrating Swedish kites at Stevns. (East Zealand). The Danish and south Swedish breeding birds overwinter primarily in Spain and France. Winter-feeding in Sweden has caused that still more south Swedish kites overwinter close to the breeding area, and the red kite is also observed in Denmark in winter in rising numbers.
The red kite has a broad choice of food, but it is especially known to be an expert in finding and eating carcasses.The bird has an important role as "nature's garbage man". But it is also able to hunt and kill its prey by itself. The young ones are especially fed with fresh-caught amphibians, reptiles, mice, rats, hare kittens, little birds, crow-birds and seagulls. The kite takes the prey, which is represented in large numbers at the breeding ground.
NB: As scavengers, red kites are particularly sensitive to poisoning. Illegal poison baits set for foxes or crows are indiscriminate and kill protected birds and other animals.



Crow pursuing a red kite
photo: grethe bachmann July 2008

History.
In the United Kingdom red kites were once so common that William Shakespeare once described London as "a City of Red Kites and Crows". King James II of Scotland decreed that they should be killed "wherever possible", but they remained protected in England and Wales for the next 100 years as they kept the streets free of carrion and rotting food. Under Tudor "vermin laws" many creatures were seen as competitors for the produce of the countryside and bounties were paid by the parish for their carcasses.

Source: Natur og Fugle, Dansk Ornitoligisk Forening

photo ⓒ: stig bachmann nielsen naturplan foto & grethe bachmann naturplan foto