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Vocapedia > Time > Seasons





Why Do We Have Different Seasons?        Video        California Academy of Sciences        29 August 2015


Did you know that the Sun’s light shines differently on Earth

at different times of the year?


In this visualization watch as the Earth orbits the Sun, rotating,

like a slightly tilted, spinning top.


This rotation changes the angle

at which sunlight hits the surface of our planet,

creating the different seasons we experience here on Earth.


Can you see how sunlight at different times of the year

changes the productivity of life on land and in our oceans?



















Seasons        Earth Rocks!        10 February 2015





Seasons        Video        Earth Rocks!        10 February 2015


Review of the causes and impacts of Earth's seasons

on daily light cycles and heat input.


Designed for an introductory oceanography course.






















Fog rises off a lake in Highlands, New York

on Saturday, Oct. 3, 2009.


AP Photo/Mike Groll


Boston Globe > Big Picture

Autumn scenes        9 October 2009
















season        UK












Why Do We Have Different Seasons?

Video        California Academy of Sciences        29 August 2015











Video        Earth Rocks!        10 February 2015

Review of the causes and impacts of Earth's seasons

on daily light cycles and heat input.










silly season        USA










during the festive season


























spring        UK / USA


















early spring        UK






in the spring of 1925





last spring
















summer        UK










































summer        USA



















1967 > USA > summer of love        UK / USA








Britain's wettest ever early summer        UK        2007






summer solstice        UK


The summer solstice,

the northern-most apparent position of the sun














on the summer solstice        UK






throughout the summer





over the summer





summer of discontent        USA











Indian summer





freak summer        UK
















autumn (UK)   /   fall (USA)





















Spring may lose song

of cuckoos, nightingales

and turtle doves


Scientists are struggling to explain
a catastrophic decline in the number of birds
whose annual visits are part of our folklore


Sunday 24 April 2011
The Observer
Robin McKie, science editor
This article appeared on p12
of the Main section section of the Observer
on Sunday 24 April 2011.
It was published on guardian.co.uk
at 00.06 BST on Sunday 24 April 2011

Some of Britain's most cherished spring visitors are disappearing in their thousands. Ornithologists say species such as the cuckoo, nightingale and turtle dove are undergoing catastrophic drops in numbers, although experts are puzzled about the exact reasons for these declines.

The warning, from the RSPB, comes as the songs of the cuckoo, nightingale and wood warbler herald the return of spring. In the case of the cuckoo – "the simple bird that thinks two notes a song", according to the poet William Henry Davies – its call has become synonymous with the arrival of warm weather. It is the quintessential bird of spring.

Yet there is now a real risk that, with other migrant birds from Africa, it may no longer make its annual appearance in our woodlands, said Dr Danaλ Sheehan, a senior RSPB conservation scientist. The call of the cuckoo could be silenced in the near future unless scientists can unravel the causes of the drastic decline in their population, she said.

According to Sheehan, numbers of migrant birds from Africa have declined dramatically in the UK since 1995. For turtle doves the figure is 71%; nightingales, 53%; and cuckoos, 44%. "That is a very significant and very worrying decline," she added.

"The real problem is that there are so many different possible causes for these losses – which makes it difficult to tease out the factors involved in their decline and to prepare plans to put things right.

"These losses could be the result of changes in farmland use in Britain which are affecting the way these birds breed when they arrive here in spring. Or they could be due to the spread of human populations in Africa and the destruction of natural habitats where they make their homes in winter.

"Climate change is almost certainly involved as well. Our problem is to unravel those different causes and assess how they interact."

In a bid to explain what is happening, the RSPB and groups such as the British Trust for Ornithology have launched a series of projects in the UK and in Africa. These include new surveys of numbers of different species arriving in Britain as well as studies, in Africa, of sites that provide winter homes for these birds. Targets will include the cuckoo, nightingale and the turtle dove as well as the wood warbler, garden warbler, whinchat, and pied flycatcher as well as the swift – another popular visitor. Its numbers have dropped 30% since 1995.

"The global pressure for land has now become extreme, and it is starting to have real implications for long-distance migrant birds," said Andre Farrar, the RSPB's campaigns manager. "Climate change – which affects timings of breeding cycles – is another critical factor."

However, the work will be tricky thanks to the complexity of bird migration between Africa and Britain. For a start, these visitors have their winter homes in very different areas. Some birds, like the nightingale, cuckoo and swift, winter in humid western regions – including Nigeria and Ghana – while others, like the turtle dove and yellow wagtail, winter in the dry Sahel area in countries such as Chad. "Both regions are affected by rising populations of humans, but in ways that will have subtly different effects on land use and on individual bird species," said Sheehan.

On top of changes of land use in their wintering grounds, scientists suspect that many migrants are finding it increasingly difficult to feed themselves when they come to breed in Britain. For example, cuckoos eat large moths and it is known that in recent years numbers of such insects have dropped significantly in the UK.

There is almost certainly a significant problem caused by climate change. Migrant birds arrive and breed and then have chicks at times which are no longer synchronised with the best periods when food, such as insects, is available. Again this is likely to have a serious impact on population numbers.

On top of these factors, turtle doves and nightingales are affected by the loss of sandy scrubland on which they like to breed. Intensification of farming has seen major reductions in this sort of habitat and this has had an impact on migrant birds, added Sheehan.

There are factors involved from outside either Africa or Britain. "Adding insult to injury to the effects of this land use and climate change is the massive slaughter that takes place in spring and autumn when birds, flying from and to Africa, cross islands in the Mediterranean Sea, such as Cyprus and Malta," added Farrar. "There they are shot, in their hundreds of thousands, by hunters – who just enjoy killing them for the 'sport'. It is against EU law, but that doesn't stop it happening."

Migrant birds from Africa clearly face a barrage of problems, although the effect of these will differ from species to species. The crucial point, say ornithologists, is that some of the most welcome visitors to the United Kingdom are now disappearing.

"Some of these birds are closely woven into our culture, like the cuckoo," added Farrar. "Others – like the spotted flycatcher, which specialises in living in old leafy churchyards and large gardens – are less well known but loved passionately by small groups of people who are very possessive about them and who watch out carefully for their return every year.

"And that sums up our attitude to migrant birds. We are at the northern edge of their ranges. However, they breed here and we identify them as being British, though it could just as easily be argued they are African or simply birds of the wild skies. Nevertheless, we have a deep, complex relationships with these creatures."

This point was backed by Sheehan. "These birds arrive in our countryside just as the first good weather arrives. We associate them with spring and warmth. That is why they appear so often in folklore. They are part of our culture – which makes the declines in their numbers so worrying. We have got to find out what is going on as soon as possible.

"Many people will hear their first cuckoo of the year this weekend. It is not guaranteed they will be able to do that 10 years from now."

Spring may lose song of cuckoos, nightingales and turtle doves,










Related > Anglonautes > Vocapedia




space, astronomy > Earth


orbits > elliptical orbits




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