The graphs illustrate changes in the populations of pigeons, swifts and barn owls between 2010 and 2019, as well as changes in their preferred nesting locations. Overall, pigeon and swift populations increased, whereas the number of barn owls declined considerably. In 2010, there were approximately 500 pigeons. Their population rose steadily and reached a peak of around 675 in 2017 and 2018, before falling slightly to 650 in 2019. Similarly, the swift population grew from just over 300 to about 460. By contrast, barn owl numbers dropped continuously from approximately 500 in 2010 to only 300 in 2019. These trends were probably caused by the town’s expansion. Many surrounding green areas were developed, reducing the amount of natural habitat available. The proportion of birds nesting in natural sites fell from 80% to 50%, while the use of man-made structures increased from 20% to 50%. In the future, pigeons and swifts may continue to increase because they can adapt to urban environments. However, barn owl numbers are likely to fall further unless natural areas and suitable nesting sites are protected.

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