EA101 – Field Ornithology, class IV

Last night was the 4th of 7 classes in the first half of CCSF’s Field Ornithology class, taught by Joe Morlan. This was the first class after our inaugural field trip last Saturday (see my blog on that), and folks naturally had some questions about the birds we’d observed

I brought some photographs of gulls I had been unable to identify, and Joe quickly pegged them as Western and California (both relatively common hereabouts) – this despite several fairly long threads on BirdForum in which it was attempted to identify them to no avail!

Topics covered last night (in no particular order) included:

Subspecies and clinal differences:

• species in one extreme of a region that differ noticeably from those in another region, but for which there is no clear line separating the populations are referred to as “clinal differences”
• Species groups that don’t overlap in range, and exhibit differing characteristics, are called “allopatric.”
• Species whose different-looking groups do overlap, but which do not interbreed or produce a zone of hybridization are called “sympatric.”
• A subspecies must havea unique breeding range not shared with other ssp’s
• Subspecies are primarily a means of describing geographic variation

Three Rules of Geographic Variation (among widespread, warm-blooded invertebrate species):

1. Bergman’s Rule (?sp):
   • Body size is inversely proportional to environment temperature
   • this is due to thermal retention – surface area increases by the square, while volume increases as the cube, so larger animals have proportionately less surface area, which makes it easier to stay warm
2. Allen’s Rule (?sp):
   • short legs and short bills occur in colder climates
   • this is also due to heat retention issues
3. Gloger’s Rule (?sp):
   • Pigment saturation increases with the humidity/wetness of a region
   • not well-understood why this is

Color morphs (formerly “phases”)

• do not change over time
• are not subspecies
• are not sex-related differences
• are not age-related differences
• are otherwise unexplained individual variations

Assortive mating

• Positive: individuals prefer to mate with individuals that look the same
• Negative: the opposite of Positive, duh 🙂

Cold vs. warm water

• cold water has more nutritious organisms since it has more oxygen (think of boiling water, which is shedding oxygen as it boils)
• at the continental shelf west of the California shore, cold water upwells and you often see many birds feeding here
• don’t take a pelagic trip from SF to the Farallones unless you enjoy seasickness – go from Monterey instead since it’s ~10mi to the shelf vs. >30mi from SF, and in much choppier waters.

Fox Sparrows:
– most seen in the SF Bay Area are of the “Sooty” ssp.

Quail

• have articularted toes to assist tree climbing
• if you hear a “quail” call in northeastern SF, it’s probably a Starling or Mockingbird, as most SF California Quail have been decimated by feral cats
• chicks are precocial and can fly when they’re still downy and half-grown, unlike most birds, which need to be roughly adult-sized before flight

Grebes

• have flaps of skin on each toe, but don’t have webbed feet
• have no tails, which is unusual for a diver
• hold air in their body feathers, which they expel, along with the air in their air sacs, to assist diving
• can’t walk on land due to their legs being very rear-mounted
• Clark’s & Western Grebes’ bill color is primary means of separating them
• Clark’s & Western Grebes were originally separate species, then were lumped into one (Western Grebe), then split again in the 1980s when a researcher found that they exhibited positive assortive mating
• Western & Clark’s Grebes are expanding in California
• Western Grebes call “creek creek” while Clark’s call a single “creek”
• Both Western & Clark’s Grebes breed in large numbers in Bridgeport, California (east of the Sierras)

Albatross

• have forward-facing tubes on either side of their bill
• eat mostly squid etc., at night
• have rear-mounted feet, and so need a running start for takeoff
• have a second wing joint, called an “elbow” (the joint that all birds have is analogous to the “wrist”)
• 3 of 4 toes are webbed
• there are many more tube-nosed birds (Albatross, Petrel, etc) in the southern hemisphere than the norhtern since there is much more water there, and the “doldrums” (an area of low/no wind at the equator) prevents them from mixing.
• the feathers between the body & elbow of an albatross are called “humoral feathers.”
• Albatross are mostly unafraid of people since they’ve only rarely encountered them (and eat their garbage when jettissoned from ships)
• lay one egg
• parents forage on the open ocean, feeding the young ‘un to obesity (it weighs more than its parents at this point!).
• the offspring is then abandoned, and must learn to fly and forage on its own
• once fledged, the young stay away from their birth island for around 6 years, then return to it to mate
• parents and young can find their nesting island from great distances, even when humans interfere
• Albatross (and other tube-nosed ocean-dwellers) exhibit “dynamic soaring” where they tack into the wind to gain lift, then do a 180 to get a push as they slowly descsend, doing another 180 to rise again once they near the ocean surface. This allows them to progress in the direction of the wind without expending much energy at all

Shearwaters, Fulmars, Petrels

• have nose tubes a la albatross, but they’re together at the top of the nose
• Norther Fulmar is hugely variable
• look somewhat gull-like, but chunkier, and with distinct flight patterns
• N. Fulmars have light, dark, and everything-in-between morphs