Adam Paul

Tuesday was another informative class in the 14-class series on Field Ornithology I’ve been taking from CCSF, although Joe has picked up the pace considerably so we can finish going through the National Geographic Field Guide to North American Birds by our last class, which is also the next class. Detailed notes follow.

Woodpeckers

• Hairy Woodpeckers are expanding their range in California, now breeding in San Francisco and the Central Valley
• Acorn Woodpeckers:
  • Have a unique and complicated communal breeding strategy:
    • Groups communally forage, store acorns in “granaries,” have communal nests, and jointly defend the commune’s territory
    • Exhibit cooperative breeding:
      • Up to 6 Males (brothers & fathers) and 3 Females (sisters or a Mother and her daughter) inhabit the nest, along with non-breeding “helpers”
      • Offspring remain in the nest for several years as “helpers”
      • Nearly all individuals in the nest are related, except for the breeding males and females – this is to prevent incest.
      • When an opening occurs in the group, a “power strugle” erupts between the same-sexed helpers to determine who will become a breeder
• Woodpeckers have 2 toes forward and 2 toes backward, which is called “zygodactyl”
  • Except for the 3-toed Woodpeckers
• Have stiff, pointed tail feathers and a chisel-like bill
• Their tongue bones are verrrrry loooong, running asymmetrically around their skull.
• The tongue is highly extensile so they can get to wood-boring insects
• Flickers have sticky tongue secretions to snare ants, their favorite food, other species of Woodpecker have barbs or bristles to get a their favored prey
• No woodpeckers have down feathers at any age(!)
  • No, not even the Downy or Hairy Woodpecker…
• Northern Flicker:
  • Juvenile is browner overall. Both M & F juv. Flickers have a moustachial stripe, which only the adult Male has.

Q: Why are the Males of so many bird species brightly-colored?

• You’d think it would make them easier prey and that natural selection would select against the brighter individuals
• But sexual selection trumps natural selection in this case, and females prefer the brighter-colored fellows in nearly all cases. Oftentimes, this is because bright plumage indicates good health and diet, which is clearly an advantage
• By the same token, juveniles of most bird species that have brightly-colored adult males look more like the adult female since this is better camouflage, and the color only assists with breeding, which the juveniles aren’t doing yet
• So why do juvenile woodpeckers look more like the adult male?
  • Nobody knows!

The biological species concept works well for birds, but is useless for asexually-reproducing organisms like plants, since it’s based on reproductive compatibility, something that doesn’t apply to life forms that are capable of fertilizing themselves!

Passeriformes (Songbirds)

• 3 toes forward, 1 toe back
• Have a highly-developed syrinx (the equivalent of a voicebox on a bird)
• This order includes 1/2 of the world’s bird species
• Divisions of passeriformes into families is more for organization than due to large biological differences – birds in this order are much more closely related to each other than birds in other orders.
• All have altricial (blind and naked) young

“Sibling” or “cryptic” speices:

• 2 species which look the same or almost the same, but are reproductively incompatible (eg. Pacific Slope Flycatcher and Cordilleran Flycatcher, which can only be told apart by their song)

Tyrant Flycatchers

• New-world Flycatchers
• Were named “Tyrants” due to their aggressiveness towards raptors
• Flycatching: the act of catching insects mid-air, leaving from a perch and returning to the same or a neaerby perch (unlike, say, swallows and swifts, which catch insects mid-air, but do not repeatedly take off and land on a perch while doing so).
  • Many other birds besides flycatchers engage in flycatching.
• Many flycatchers look very similar and are quite closely related
• Songs are believed to be innate, not learned
• Most Tyrannidae have “rictal bristles,” stiff bristles at the base of their bill
  • these bristles’ function is not known, but is thought to either assist with catching prey, or keep debris out of their large eyes

Shrikes

• Loggerhead and Northern are the only two native to the US
• Loggerhead Shrike is on the verge of extinction in Eastern states, and declining elsewhere. No one’s quite sure why – it’s not pesticides or habitat loss…
• Are predatory birds that feed on insects, small birds, and rodents
• M & F are identical
• M store prey by impaling it on thorns (or barbed wire) and storing it for later consumption
  • This habit earned them the name “Butcherbird,” and they were considered to be evil birds by early settlers
  • They do this to mark territory and to impress the ladies (“hey baby, look at my row of impaled crickets!”)
  • Shrikes were shot by the thousands by settlers who thought they were “wanton killers”
• The Loggerhead Shrike is unique to North America, although there are over 2 dozen shrike species in EurAsia

Factoid: Birds that expanded into North America via Alaska typically migrate back the way they originally came in. The Arctic Tern breeds as far south as Cape Cod, but migrates NORTH to the arctic, then over to Europe and south to Africa, since that is the route by which they expanded into North America

Vireos

• Are a New World-only group, genetically pretty closely related to Shrikes
• They’re “foliage gleaners” (they forage in leafy canopies for insects on leaves)
• Parasitism by the Brown-headed Cowbird is causing a vireo decline
• Warbling Vireos:
  • Sing from their nest, unlike most birds (one would think this would be a bad idea since it tells potential predators where the nest is!)
  • Nests are woven and hanging from a horizontal branch. They’re about the size and shape of a tennis ball.

Faunal Zones:

• Areas of special characteristics
• Neo-tropical (Mexico to S. America), Neo-Arctic (N. of Mexico), Eurasial, Ethiopal (Africa S. of the Sahara), Oriental (Asia, incl. China & India), and Australasian (Australia & the islands)

Crows & Jays:

• feed on anything that’s edible (by their definition)
• most species are common and increasing in the US due to their generalization – they can do well almost anywhere, especially Ravens, which can live anywhere at all, from the Arctic to Death Valley, except areas with a large population of Crows.
• most have nasal tufts at the base of their bill
• identifying Ravens vs. Crows: Ravens have a rounder tail, and soar, which Crows never do.
• Ravens are thought to be highly intelligent among birds, and can be taught tricks.

Skylarking: the act of singing mid-flight
Larks (did I mention we moved very quickly through families this class?)

•  The Horned Lark is the only expected North American Lark.  Sky Larks are rare vagrants.
• They’re mostly terrestrial and walk, rather than hop, on the ground
• There are many lark species in Eurasia & Africa
  • The Horned Lark is there too, but occurs only in sandy and tundra terrain, while in North America, it occurs nearly anywhere that’s open.  Why?
    • To prevent competition with the other lark species, none of which occur here in NA
    • Why no other larks in NA?
      • Because in northeast Asia, the Horned Lark is the only lark near the arctic, which allowed it to cross over to Alaska, then expand south
    • So we can conclude that the Horned Lark is probably a relatively recent arrival to North America, since no speciation events have happened to produce new lark species here, and, until such an event occurs, it will remain the only Lark in NA.
• Horned Larks lay flat on the ground in the face of danger to blend in with the dirt and rocks

Factoid: Most birds sing from treetops because sound travels farther the higher up you are.

Swallows

• migratory birds
• Barn Swallow
  • are red-bellied in North America, but white-bellied in Eurasia
  • M has a longer forked tail than F, and is a little bit more colorful
  • build mud nests, like many other swallows
  • babies gape and whine whenever disturbed
• more on Swallows next class