Sea-gulls.
If sea-gulls fly inland, expect storm.
When sea-gulls fly to land, a storm is at hand.
Snow-birds.
When snow-birds gather in flocks and light on fences and hedges, expect rain.
Storks.
If storks and cranes fly high and steady, expect fair weather.
Summer Birds.
When summer birds take their flight, the summer goes with them.
Swallow.