I have observed and recorded the arrival and departure dates of hummingbirds in my yard for the past 13 years.
It's always almost to the day the same; April 22 in the Spring; leave Sept 22 in the fall.
Makes sense. Actual research, not this kind of uncontrolled garbage, has shown that birds a) migrate according to the length of daylight, not passing weather, and b) seem to have a wired in annual periodicity which causes agitation and orientation toward the usual direction of migration at certain time frames in the year, even in caged birds in controlled environments.
The supposition that "climate change" drives alterations in these instinctive patterns makes no scientific sense. Political sense yes--students of bird behavior need grant money too you know. Might as well get on the bandwagon.