The given graph illustrates the changes in the populations of five different birds species from 1990 to 2010 in Wollai Park. Units are measured in thousands.
Overall, what stands out from the graph is that parrots are the only species whose quantity, despite fluctuations, ended at the same level as it began, while the populations of the remaining birds species examined all followed a downward trend.
Despite having a relatively similar starting point at 0.9 thousand, the numbers of crows and kookaburras underwent different levels of decline: while the former plummeted significantly by two-thirds to only around 0.3 thousand in the final year, the latter experienced a more moderate decrease, ending at approximately 0.6 thousand.
About 0.5 thousand whip birds were recorded in Wollai Park in 1990, after which it dropped to about 0.45 thousand in 1995 and fluctuated between 0.45 and half of a thousand in a decade until 2005, when this figure sank to its bottom at 0.25 thousand in 2010. As for swallows birds, the figure for this species commenced at 0.25 thousand in 1990, preceding a gradual decrease to 0.1 thousand in 2005 before recovering to north of 0.2 thousand in 2010.
Finally, with regard to parrots, the number of this species rose from around 0.75 thousand to a peak of 0.9 thousand during the first five years of the period, followed by a steady decline back to approximately its initial level of 0.75 thousand.