EA 101 – Field Ornithology, Class V

Another good class tonight, my 3rd from last in this first half of the Field Ornithology series I’m taking from CCS.

Copious notes follow:

My feathers

• The feathers I brought in might well be from a Red-shouldered Hawk, but it was considered odd that there were many dozens of the scattered about, as the few birds that might prey on a RSH do not generally pluck their meals.

Factiod #1: Red-shouldered Hawks used to be very rare between Napa county and Gilroy – it’s only been the past couple decades that they’ve become common’ish in the greater San Francisco area.

Flight Style

• undulating, straight, flock-based, etc – although a useful supporting characteristic, it cannot be reliably used to ID a bird

GISS/Gestalt

• GISS = General Impression, Shape & Size – the “gut feel” of a bird
• Although there are books devoted to this “holistic” style of identification, it’s only really of use for the more common species in an area, as detailed observations are required for rarities records to be accepted.

Bird Behavior categories:

• Body Care
• Feeding
• Social
  • Birds carrying nesting material can be considered to be breeding in the immediate area except:
    • Wrens, which build multiple nests at various times (the males do this, as the male with the most gets the women!)
    • Woodpeckers, which build their nests inside of a tree
  • Birds carrying food are also considered to be nesting in the immediate area.
  • An adult bird carrying off a fecal sac is also proof
    • Some bird young defecate into a white gel-like sac that they then present to their parents (lucky them!), who carry it away for disposal!

Nesting times for some common birds:

• Mourning Dove: April-November
• Pied-billed Grebe: from late November onward
• Great Horned Owl: February & March
• Anna’s Hummingbird: December onwards
• House Sparrow: pretty much all year long (in California)

Most birds only use their nest for nesting activities, not for roosting or sleeping.

• This is largely for hygienic reasons, as nests collect insects/lice/parasites
• Some species will re-use a different species’ nest. Great Horned Owls often re-use Red-tailed Hawk nests, sometimes evicting their occupants.
• Brood parasites (the Brown-headed Cowbird is the most famous example) lay their eggs in a different “host” species’ nest and let that host do the incubation.

Bird Atlases

• Are used to record which birds breed, and exactly where they do so over a period of at least 5 years
• Are usually published on a county-by-county basis
• Although since it takes so long to compile the data and get it published, it’s somewhat out of date by the time it’s released, they establish a baseline that can be compared against.

Observing behavior

• Avoid anthropomorphism: just because a bird looks like it’s yawning does not mean that it is tired, as we would be when we’re yawning.
• Instead, focus on what it is that the bird is doing, and the context in which it is doing it.

Colonial Seabirds:

• disperse when nesting ends
• they leave when the food supplies on/near their breeding islands dwindle
• they go as far as they have to to find reliable food supplies, sometimes leading to some individuals choosing coastal terrain rather than islands.
• juveniles have to fly much farther, because they can’t compete with adults.
• this is why most of the colonial seabirds we see in California are juveniles.

Storm-Petrels

• Notoriously difficult to ID
• Feed on surface plankton etc.
• One can distinguish eg. Ashy & Black Storm-Petrels when they are foraging, we usually see them in escape flight when they are flushed by approaching boats. Unfortunately for us, their escape flight patterns are identical.

Pelicaniformes

• Have fully webbed feet (vs. the 3 webbed toes, with 1 “free” toe of many shorebirds)
• Magnificent Frigatebird
  • Are pirate birds – they steal the catches of boobies, terns, etc.
  • Proportionately long wings and forked tail allow them to out-manouver their victims
  • They are superb fliers, with an 8-foot wingspan and only a 3-pound body weight. Compare this to the American White Pelican, which also has an 8-foot wingspan, but a 15-plus-pound body weight!
  • The males’ red throat sac is purely decorative and puffed out during breeding times
  • They’re only very rarely seen in California, and then mostly juveniles in extreme Southern California
  • Despite their webbed feet, they cannot swim! Can’t plunge either, so the only way they can catch any food other than stealing it is by eating flying fish when they come out of the water!
• Tropicbirds
  • Are very rare in Northern California
  • Are somewhat gull-like, but have very long central tail feathers
• Factiod #2: A “brood patch” is a bald spot on the chest of many nesting birds that allows them to more efficiently transmit body heat to their eggs
• Boobies
  • Do not have a brood patch, but rather keep eggs warm by warming their feet in the sun and wrapping them around the eggs
  • Eat their food (fish) head-first due to the orientation of fishes’ gills
  • Do not chew their food, but store it in their gullet for later digestion
  • The name “Booby” comes from the Spanish “bobo” for “stupid”
  • They plunge-fish, like pelicans do
  • Their nostrils are fused shut – they are obligate mouth-breathers. A small flap at the corners of their mouthes allows them to breathe when it’s open, and be sealed off when diving
  • One Blue-footed Boobie was found in New Hogan Reservoir in the north-central Sierra Nevada foothills in California(!!).
• Pelicans
  • American White Pelicans and Brown Pelicans are the only two pelicans found in North America
  • Brown Pelicans are on the federal endangered species list.
  • One might wonder why this is, as especially on the Pacific Coast in California, they’re pretty abundant!
  • The answer lies in their breeding status – although they used to breed all along the Pacific coast as far north as Monterey, there are no breeding Brown Pelicans in the west coast now – all of the ones we see have come from Mexico.
  • Breeding populations left due to DDT buildup (particularly a problem in such long-lived birds as pelicans) causing thin-shelled eggs. This did not result in egg breakage, as might be imagined, but rather in eggs drying out due to their shells being too permeable.