Seabirds

1. Seabirds Lecture 10

2. Common Groupings of Marine Birds • Seabirds—e.g. penguins, pelicans, gulls, terns • Capable of feeding away from shore • Breed on islands or coastal zones • Shorebirds—e.g. sandpipers • Feed on shorelines in sand/mud • Wading birds—e.g. herons, egrets • Freshwater or marine • Marsh birds • Hunters

3. Seabird Diversity • 27 orders of birds—10,000 species • Four contain “true” seabirds • Sphenisciformes—Penguins • Procellariformes—Albatrosses, Petrels • Pelecaniformes—Pelicans, Cormorants • Charadriiformes—Gulls, Terns

4. Representative Families Family Sternidae: Terns—45 species • Slender, rapid wings • Smaller than gulls • Broad tail, often V-shaped • Feed on fish at surface • Many species highly migratory Royal Tern

5. Representative Families Family Laridae: Gulls—56 species • Intelligent • Often adaptable to human disturbance • Generalist carnivores • The least specialized of all seabirds • More generalized morphology Laughing Gull

6. Representative Families Family Pelecanidae: Pelicans— 8 species • Feed on fish at surface • Gular pouch on lower jaw • One of the heaviest flying birds • Brown pelican is smallest species Brown Pelican

7. Life History—Nesting • Generally occurs at inaccessible coastal areas • Isolated islands, cliff faces, coastal wetlands • Two reasons— • Large nesting colonies • Adults return to natal area • Both parents involved with care

8. Life History—Offspring • Egg incubation  25-35 days • Fledging period  1-2 months • Juvenile seabirds often different plumage color • 4-5 years until maturity Royal Tern Creche

9. Seabird Foraging—Gulls • Unhinging jaws— • Take live prey • Tool use • Baiting, breaking shells • Plunge diving • Scavenging— • Kleptoparasitism— • Advantages of walking ability? Starfish Crabs Mussels Herring Gull Dutch Colony % of diet Spring Summer Fall

10. Seabird Foraging—Terns & Pelicans • Plunge diving—pelicans • Only two species dive • Impact on left side— • Impact may stun fish • Pelicans may also feed from surface • Air sacs beneath skin and in certain bones— • Plunge diving—terns • Hovering • Scavenging

11. Seabird Foraging—Terns

12. Seabird Foraging—other methods Northern Gannet Dive from up to 100’ Depth of up to 50’ Swim with wings/feet

13. Seabird Foraging—other methods Wilson’s Storm Petrel Most abundant bird Feeds on inverts and small fish

14. Seabird Plumage Coloration • Generally drab coloration • White, black, gray, brown • Often countershaded • Adaptive significance poorly studied—hypotheses?

15. Bird Wings—overview • Wings shaped like airfoils— • Secondary feathers lift • Primary feathers generate power—forward motion • Greater flexibility of motion • Connect to “hand” bones • Large range of motion Wing cross-section Lift

16. Seabird Wings—high aspect ratio • Seabird wings not “slotted” to reduce drag • Extended secondary region increases lift • Highapect ratio • Good for soaring (gliding) • Drawbacks? Tern Albatross Grouse Vulture

17. Seabird Wings—high aspect ratio Dynamic Soaring

18. Seabird Wings—High-speed wings • Streamlined • Greater proportion  primary feathers • Good for sustained, high-speed flying • Hovering • Energetically expensive Tern Albatross Grouse Vulture

19. Seabird Osmoregulation • Nitrogenous waste Uric acid • Effective kidneys • Salt Gland— • Many seabirds still require some freshwater • Pelagic seabirds months to years at sea

20. Seabird Conservation • Loss of nesting habitat • Increased disturbance • Invasive species—nest predation • Oil spills

21. Seabird Conservation • Interactions with fishing gear • Long lines • Gill nets • Recreational entanglements • Plastic pollution in ocean

22. Seabird Conservation—Success stories Brown Pelican • Listed as endangered—1970 • Delisted 2009 • DDT outlawed in 1972 Laughing Gulls • Nearly extirpated in U.S. • Late 1800s • Plume hunters