Problem
I. Which sites are you using? Your question is asking whether urbanization affects pigeon population. So you need to find different levels of urbanization and measure whether the pigeon count changes as urbanization changes. If you are looking only at parks that all have same amount of urbanization, you won't be able to compare anything.
One solution is to make sure each park (which I'm assuming is the "less urban" space) is paired with a nearby urban/polluted area (such as a high-traffic neighborhood) and see how pigeon populations change between them.
II. When and how will you measure pigeon population? Come up with a schedule and method to count pigeons. (And avoid counting any one pigeon twice... there may be suggestions online for how to do this).
III. Regarding your hypothesis- make sure you are basing it off of research. You should have a scientific explanation behind your hypothesis. Also, frame your hypothesis as an educated guess: "Urbanization increases pigeon population..."