I’m in California/ Northern Sierras, and every year in May the American white pelicans fly over the house heading east away from their winter habitat in the valley. I’m lucky that I’m right on the migration path that I can spot them every year.
This year they set out earlier than usual, around mid April. Typically I’ll see 3 to 5 larger flocks “10 - 20 birds” every other year, this year I saw only three smaller flocks numbering 10 and under, and towards the middle of May I saw two small groups actually flying west back towards the valley, most likely deciding to head for the coast.
We didn’t have bird flu reported over the winter so the only cause I can think of is the drought the state has been expieriencing. We also have had more land disappearing due to becoming housing developments in the valley. If other animals like predators were displaced into the remaining wildlife areas that could be another issue.