Common Tern nests may feature a pile of dead vegetation, but many birds use no nest at all, simply laying eggs in a scrape on the bare ground. The birds nest in colonies called ternaries, which can range in size from tens to thousands of birds.
Eggs are olive to buff in color, and marked with brown spots and blotches concentrated around the larger end. Clutch sizes range from 1-4. Both parents incubate the eggs for 27 days; chicks fledge about 21 days after hatching.