The Sibley Guide to Bird Life and Behavior

Well, Sibley illustrated this, but most of Part 1: The World of Birds (the good stuff!), was written by the other editors of this book– Rick Cech, John Dunning, Chris Elphick, Margaret Rubega. I learned a ton of crazy things just in those first hundred pages, which is why I’m doing the write-up now, while I still skim & dance through the remaining 500 pages about the individual species.

* Curlews and other shorebirds that probe for food below the soil– their bills contain tactile sensors to help locate prey. They can feel with their bills!
* To land after flying, birds adjust their wing feathers to create more drag, to slow down, hover, land.
* We’re not sure of the purpose of the rictal bristles near the mouth of certain fly catchers. “Experimental removal” (ouch) doesn’t affect their ability to catch prey, but they could act as an eye protectant.
* Also have tactile sensors in tongue to identify food and know where to position it to crush and swallow (birds don’t have teeth).
* Digestion happens quickly– 30-45 minutes
* Gizzard is lined with rough keratin and sandy grit ingested by the bird; both are used to pulverize the food… acting as teeth
* The gizzard changes based on season! Toughens to handle seeds in winter, softens to handle insects in summer.
* Longer intestines in plant-based diet birds gives the digestive system more time to pull nutrients from veg that’s difficult to extract nutrients from
* Towhee’s gut length increases in winter to accommodate a switch in diet.
* Bird bones are hollow but reinforced with complex strut mechanisms
* Birds see in the UV and near-UV range which humans eyes can’t detect. 1990s studies on kestrels show them using UV light to hunt for mice– mice use urine to mark their trails, urine absorbs UV light, areas of concentrated urine (mouse trails) appear as black lines. Falcons can thus see the trails very distinctly, just sit back and wait for a mouse to appear.
* Syrinx – the vocal organ, is connected to 2 tracheal tubes, so birds can produce two distinct sounds at one time.
* Birds have ability to detect magnetic field of Earth, believed b/c of tiny crystals of magnetite near their olfactory nerves.
* I’ve always wondered why certain groups always flock together– white crowned sparrows hanging with fox sparrows hanging with song sparrows and golden crowned sparrows… these were all at one time the same species, then isolation caused evolutionary distinctions, but if they don’t compete for resources then they can peacefully coexist.
* White crowned sparrow must eat seed every 4-5 seconds to survive winter.
* Migratory activity requires high high energy. Continuous flight for 2-6 days without rest, the human equivalent of running a 4 minute mile for 80 hours straight.
* “Birds have light receptors in the brain that are sensitive to the extremely low light intensities that penetrate into the brain itself. Birds sense the length of day and night with these receptors rather than with their eyes. Stimulation of the brain receptors in the spring initiates a series of hormonal changes that results in production of testosterone in the male and estrogen and other hormones in the female. These physiological changes in turn orchestrate a complex suite of seasonal behaviors that determines the timing of reproductive activities, migration, and molt.”
* Migratory efficiency– most important variable is wind strength and direction. Migrants actively choose to migrate at times with appropriate wind direction and select flight altitude to minimize headwinds and capitalize on tailwinds. Flocks also get aerodynamic advantages with flocks– drafting.
Books to check out:
* Herring gull’s world
* Ravens in winter