All species, be they resident, visitor or migrant, have their own specific habitat preferences. Some like the Starling Sturnus vulagaris can be found in most habitats yet others like the Spotted Crake Porzana porzana are much more catholic in their requirements. To understand why birds are recorded where they are we need to have a wider knowledge of the geography of the region. The following sections describe the basic geology of the county, how its landscape has evolved and why the numbers and types of birds are where they are.
Geology Geological map of Northamptonshire
All rocks found in Northamptonshire are sedimentary. More than 100 million years ago, the Midlands and Southern England were under the sea. A process of submersion and uplifting recurred several times, each time a new layer of sediment was laid down.
The Northamptonshire Heights are part of the great line of limestone hills that stretch from Yorkshire to the Dorset Coast. The Cotswolds and North York Moors are more distinct from their surroundings than the lower and less striking Northamptonshire Heights. The whole of this geological zone is known as the Jurassic System. The only igneous rocks found in the county are pebbles and small boulders, which were carried here during the great Glacial periods. Much of the county is covered with rock debris deposited during the great Ice Age. The Ice Age considerably affected the landscape. It rounded off the hills where they were capped by soft rocks and shaped many river valleys. The river Nene has a very broad valley east of Northampton. This was probably caused by the enormous amount of water that was released by the melting ice. Gravel pits often indicate glacial deposits and the Nene valley certainly has its fair share.
Geography Altitudinal map of Northamptonshire
The county can be divided into three parts:
1) The first region consists of a hilly area in the south-west, which joins a ridge of hills running from Daventry in a north-easterly direction and ceasing abruptly near Stamford. This area contains all the highest land in the county. The highest points are Arbury Hill(735ft), Borough Hill near Daventry(635ft), and Honey Hill near Cold Ashby(>700ft). The south-east slope of this range of hill is not as steep as the scarp slope of the north-west face. This high land is the source of several important rivers. The Welland, Nene and Ouse all flow eastwards to the Wash. The Avon flows west to the Severn and the Cherwell flows south to join the Thames.
2) The second region of hills divides the River Nene from the River Ouse. None of this land that runs from Deanshanger to Raunds is particularly high.
3) The third area is the central core of the county: the valley of the River Nene. The source of the river is generally regarded as Hartwell Spring, near Staverton Lodge that is just to the north of the countys highest hill - Arbury Hill. It appears as a proper stream about a mile away at Badby. From its source to Northampton the river falls 300ft in 17 miles, in the remaining 100 miles it falls less than 200ft. After the two main feeder streams join at Northampton the river is slow flowing, has a wide valley and is prone to flooding. There are no sizeable south bank tributaries but three main north bank tributaries: the River Ise, Harpers Brook and Willow Brook. From Northampton to Peterborough the river is canalised with 37 locks.
The average rainfall is between 58-63cms (23-25inches) with slightly more the further west you travel. Rainfall is spread throughout the year and falls on about 175 days. The average daily temperature in January is 7oC(44oF) and in July 21oC(70oF). The temperature will rise above 27oC(80oF) on about 8 days and on average there will be 65 frosts.
During the later part of the Old Stone Age, after the last glaciation, Northamptonshire was probably heavily wooded, especially on the valley slopes whilst the valley bottoms were swampy and largely impassable. The thickest forests were in the north-west and south-eastern parts of the county. The summits of the Northampton uplands provided the best conditions for life of early people. In the New Stone Age about 4500 years ago there were several settlements in the western half of the county along the valley slopes, but still humans had little influence on the landscape. During the Bronze Age about 4000 years ago the numbers of people in England increased who farmed using plough and oxen and who also relied on cattle but not in significant numbers in Northamptonshire.
By the Iron Age 2500 years ago Northamptonshire was still a gloomy forested country with only a few scattered villages and rough tracks. The settlements were largely along the valley slopes of the Welland, Nene and Ouse. It was not until the Roman invasion in 43 AD that man had a significant influence on the landscape of Northamptonshire. For the following 400 years the Romans were overlords of all the Celtic villages in the county. As the settlements gradually developed, the forests were reduced and the amount of cultivated land increased. A few good through roads were constructed to move food and troops and local roads were built to collect taxes (in kind). Most settlements were along the Cherwell and Nene valleys and the Northampton Uplands were still heavily wooded and were avoided.
The six hundred years between the end of Roman influence and the Norman Conquest saw the development of the blueprint for what we see today. The Angles used the river as routeways into the interior of Britain and many new settlements were set up along the river valleys. During the invasions by the Danes, Northamptonshire was a key defence district for the Kingdom of Wessex. The Open Field System of land cultivation meant that arable land was divided into large areas with little or no hedges and this continued for several centuries.
By the time of the Norman Conquest nearly all of our present villages had been established and great areas of our forest had already been cleared. During the 12th century a few villages appeared in the north-western uplands but the Rockingham, Salcey and Wittlebury Forest areas were very sparsely populated. Our parish boundaries have changed little since Norman times. The 13th century saw the first great rise in the population.
The Black Death in 1348-9 reduced the work force and small farms became more common place. The lack of labour also saw the increase in sheep farming. With more need for land as a result of a growing population and need for land for sheep farming, much of the forest had been cut down by 1500. The enclosure of the common land by the lords and new farmers for sheep farming saw an increase in hedges. The enclosures proceeded more rapidly in the 16th century and continued intermittently until the 19th century. Cattle rearing grew in importance in the 16th century and some efforts at draining the fens were made, although little was accomplished. In the 17th century Dutch engineers came to the region to assist in the draining of the fens and were considerably more successful.. Until then the fenmen around Peterborough and Ely had caught a multitude of wildfowl for sale at local markets.
The 18th century saw a large increase in population due to improved conditions of life. The end of this century saw another surge in enclosure of common land and improved methods of agriculture. The Industrial Revolution saw a great extension of the factory system and by 1800 only a third of the population was directly employed on the land. The 19th century saw a rapid industrial expansion and trade between countries creating a lack of need for agricultural produce. In the latter part of this century much of Northamptonshire was turned over to pasture.
The 20th century has seen a massive increase in land use for residential, commercial and industrial areas linked to an ever expanding population. Land use has and will continue to be variable in response to fluctuations in population needs. In 1870, 50% of the county was under the plough. This percentage fell to 25% between the wars and increased to 54% by 1995. Farming requirements have changed again in the last quarter of the 20th century. Larger fields are required and consequently there has been a significant loss of hedgerows and those that are left are often severely managed.