On the east coast of the United States (and in France), pollution causes the plants to mutate to release a deadly neurotoxin that causes people to kill themselves. But on the west coast of the States, the same pollution mutates the birds so that they become Made of Explodium and gain acid spit. Both events happen at around the same time, which is why we don't hear of one in the other - both sets of protagonists are on the run for the most part, and the news stations are too busy reporting about their own areas to worry about what's happening in the rest of the world.
Five years after Johnny's suicide, Denny's made a pretty good living for himself - he changed his name to Rod to get a fresh start, and he got a stable job as a software salesman. But as soon as he sees Nathalie in the diner, he's instantly reminded of Lisa, his first crush - so he runs after her, makes up a lie about them going to school together, and basically acts like a huge creeper. Nathalie originally goes on a date with him out of pity, but they find themselves genuinely attracted to one another, and it's The Power of Love that allows them to get through the Birdemic. The rest of the cast of The Room dies in the Birdemic, except for Mark, who moved away to get away from Lisa - he later became a playwright, and wrote and starred in a production of Johnny's life, called "The Room".
- Alternately, the Birdemic is Johnny's karmic revenge on San Francisco and all who wronged him.
He came from the future with the secrets of cheap and effective solar power as part of the plan to stem the exploding bird apocalypse, but his difficulties in properly emulating human behavior (and inability to correctly pronounce "solar panels") cost him valuable time.
- Or he's more like Kyle, in that he came back to the past to sleep with Nathalie so she could become pregnant...with himself! The inbreeding inherent in him being his own father might explain why he's the way he is.
- Granted they're built to kill humans, not birds, but wouldn't a Terminator be a better shot than Rod is?
- The Resistance found Rod in a dumpster. He'd been rejected at the factory due to faulty programming. Hence the bad aim and social awkwardness.
Though it's too early to tell at this point, the first teaser trailer is a parody of the shawarma stinger from The Avengers. This does not bode well.
- This movie is so grievously, horrendously awful in its messaging that at first I thought it was a very VERY sad attempt at making a reverse-psychology Author Tract against environmentalism.
With the terribly written lines, the horribly developed romantic subplot, the poorly done action scenes, and the tacked-on Authors Tract, it's like the director wanted to make a story based on The Birds but instead of writing it, he made a movie instead.
Climate change does exist within Birdemic (as evidenced by the characters going to see An Inconvenient Truth), but the specific references to "Global Warming" refer to an eco-terrorist group of the same name, one that was relatively notorious for whatever reason. At some point before the films, the group had found the fossils of a rather unusual species of birds: ones that had developed acidic sacs in their bodies, which they could expel to deter predators but made them prone to exploding. Realizing they would make perfect shock troops, Global Warming the group hired Mad Scientists and had them modify contemporary eagles and vultures with similar adaptations, then sent them to attack the town of Half-Moon Bay as a test run.
The red rain of Birdemic 2 was also an invention of Global Warming the group, created after the previous batch of birds all exploded. Rather than making new birds, they decided to revive the ancient species with a Weather-Control Machine that bathed the La Brea Tar Pits with red rain, which regenerated their bodies and drove them to attack targets that were tangentially related with climate change. The runoff from the red rain also affected the Giant Jumbo Jellyfish, and it revived some zombies and cavemen when the machine passed over a cemetery.
If Birdemic 3 is made, Global Warming the group will crossbreed the exploding birds with humans, creating mutant bird-man hybrids who can better target sources of climate change. They'll also specifically target Rod and Nathalie for foiling their plans twice over, which will prompt them to go to Global Warming the group's headquarters and defeat their leader, Tippi Hedren, who's mutated herself into a Kaiju-sized bird-woman in order to kill off all humans.