I would also have to ask if you mean changes in climate as changing location due climate in terms of migrting to another location? Or do you mean how birds movement and gatherings have been claimed to be predictors of climate (weather) changes?
Birds are animals of instinct, and they migrate according to season and temperature changes. If we have an early winter or a late spring, it changes the timing of their migration patterns.
Climate change is already altering these migratory seasons, and the locations and distances to which birds do migrate.
For your paper, look for a university website (ends in .edu) article on bird migration, or search magazine databases for Scientific American or websites like the Sierra Club or Audobon Society.
I would say you first need to determine if you are writing about the normal seasonal migration of birds or if you are suppose to address the effects of global warming on the climate and how those climate changes are changing the habitats of birds in certain areas of the world.
Does this paper have to claim that the movement of birds causes climate change or is it the other way around? I assume it is climate causing bird movement that you are supposed to write about.
If you are talking about changes in the weather and bird movement, you would want to write about seasonal migration. If you are talking about long-term climate change you might talk about how rising temperatures would make various regions of the world more or less inhabitable for various species of birds (so the birds would have to/be able to move to new areas).
Supposing that you're talking about the moving of birds as a result of climate changes, there were new studies that have revealed the fact that ranges have shifted toward north. This shifting was coincidental with the period of time that recorded the increasing of global temperature.
This movement toward north raises questions, the major one being that if this shift is damaging, leading some species to extinction.